#:include "common.fypp"
submodule(stdlib_lapack_eig_svd_lsq) stdlib_lapack_eigv_sym_comp
implicit none
contains
#:for ik,it,ii in LINALG_INT_KINDS_TYPES
pure module subroutine stdlib${ii}$_ssygst( itype, uplo, n, a, lda, b, ldb, info )
!! SSYGST reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by SPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(sp), intent(inout) :: a(lda,*)
real(sp), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSYGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'SSYGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_ssygs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_ssygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_strsm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT',kb, n-k-kb+1, &
one, b( k, k ), ldb,a( k, k+kb ), lda )
call stdlib${ii}$_ssymm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_ssyr2k( uplo, 'TRANSPOSE', n-k-kb+1, kb, -one,a( k, k+kb ), &
lda, b( k, k+kb ), ldb,one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_ssymm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_strsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, one,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_ssygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_strsm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',n-k-kb+1, kb, &
one, b( k, k ), ldb,a( k+kb, k ), lda )
call stdlib${ii}$_ssymm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_ssyr2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-one, a( k+kb, k &
), lda, b( k+kb, k ),ldb, one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_ssymm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_strsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, one,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_strmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, one, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_ssymm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_ssyr2k( uplo, 'NO TRANSPOSE', k-1, kb, one,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_ssymm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_strmm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',k-1, kb, one, b( &
k, k ), ldb, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_ssygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**t*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_strmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, one, &
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ssymm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ssyr2k( uplo, 'TRANSPOSE', k-1, kb, one,a( k, 1_${ik}$ ), lda, b( k, &
1_${ik}$ ), ldb, one, a,lda )
call stdlib${ii}$_ssymm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_strmm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT', kb,k-1, one, b( &
k, k ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ssygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_ssygst
pure module subroutine stdlib${ii}$_dsygst( itype, uplo, n, a, lda, b, ldb, info )
!! DSYGST reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by DPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(dp), intent(inout) :: a(lda,*)
real(dp), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSYGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'DSYGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_dsygs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_dsygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_dtrsm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT',kb, n-k-kb+1, &
one, b( k, k ), ldb,a( k, k+kb ), lda )
call stdlib${ii}$_dsymm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_dsyr2k( uplo, 'TRANSPOSE', n-k-kb+1, kb, -one,a( k, k+kb ), &
lda, b( k, k+kb ), ldb,one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_dsymm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_dtrsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, one,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_dsygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_dtrsm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',n-k-kb+1, kb, &
one, b( k, k ), ldb,a( k+kb, k ), lda )
call stdlib${ii}$_dsymm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_dsyr2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-one, a( k+kb, k &
), lda, b( k+kb, k ),ldb, one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_dsymm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_dtrsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, one,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_dtrmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, one, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_dsymm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_dsyr2k( uplo, 'NO TRANSPOSE', k-1, kb, one,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_dsymm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_dtrmm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',k-1, kb, one, b( &
k, k ), ldb, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_dsygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**t*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_dtrmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, one, &
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dsymm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dsyr2k( uplo, 'TRANSPOSE', k-1, kb, one,a( k, 1_${ik}$ ), lda, b( k, &
1_${ik}$ ), ldb, one, a,lda )
call stdlib${ii}$_dsymm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dtrmm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT', kb,k-1, one, b( &
k, k ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dsygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_dsygst
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$sygst( itype, uplo, n, a, lda, b, ldb, info )
!! DSYGST: reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by DPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(${rk}$), intent(inout) :: a(lda,*)
real(${rk}$), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSYGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'DSYGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_${ri}$sygs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_${ri}$sygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_${ri}$trsm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT',kb, n-k-kb+1, &
one, b( k, k ), ldb,a( k, k+kb ), lda )
call stdlib${ii}$_${ri}$symm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_${ri}$syr2k( uplo, 'TRANSPOSE', n-k-kb+1, kb, -one,a( k, k+kb ), &
lda, b( k, k+kb ), ldb,one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_${ri}$symm( 'LEFT', uplo, kb, n-k-kb+1, -half,a( k, k ), lda, b( &
k, k+kb ), ldb, one,a( k, k+kb ), lda )
call stdlib${ii}$_${ri}$trsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, one,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_${ri}$sygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_${ri}$trsm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',n-k-kb+1, kb, &
one, b( k, k ), ldb,a( k+kb, k ), lda )
call stdlib${ii}$_${ri}$symm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_${ri}$syr2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-one, a( k+kb, k &
), lda, b( k+kb, k ),ldb, one, a( k+kb, k+kb ), lda )
call stdlib${ii}$_${ri}$symm( 'RIGHT', uplo, n-k-kb+1, kb, -half,a( k, k ), lda, b(&
k+kb, k ), ldb, one,a( k+kb, k ), lda )
call stdlib${ii}$_${ri}$trsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, one,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_${ri}$trmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, one, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_${ri}$symm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_${ri}$syr2k( uplo, 'NO TRANSPOSE', k-1, kb, one,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_${ri}$symm( 'RIGHT', uplo, k-1, kb, half, a( k, k ),lda, b( 1_${ik}$, k ), &
ldb, one, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_${ri}$trmm( 'RIGHT', uplo, 'TRANSPOSE', 'NON-UNIT',k-1, kb, one, b( &
k, k ), ldb, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_${ri}$sygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**t*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_${ri}$trmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, one, &
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$symm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$syr2k( uplo, 'TRANSPOSE', k-1, kb, one,a( k, 1_${ik}$ ), lda, b( k, &
1_${ik}$ ), ldb, one, a,lda )
call stdlib${ii}$_${ri}$symm( 'LEFT', uplo, kb, k-1, half, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, one, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$trmm( 'LEFT', uplo, 'TRANSPOSE', 'NON-UNIT', kb,k-1, one, b( &
k, k ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$sygs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_${ri}$sygst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_ssygs2( itype, uplo, n, a, lda, b, ldb, info )
!! SSYGS2 reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T *A*L.
!! B must have been previously factorized as U**T *U or L*L**T by SPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(sp), intent(inout) :: a(lda,*)
real(sp), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(sp) :: akk, bkk, ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSYGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_sscal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_saxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_ssyr2( uplo, n-k, -one, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_saxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_strsv( uplo, 'TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), ldb, &
a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_sscal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_saxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_ssyr2( uplo, n-k, -one, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1, &
k+1 ), lda )
call stdlib${ii}$_saxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_strsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_strmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_saxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_ssyr2( uplo, k-1, one, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_saxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_sscal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_strmv( uplo, 'TRANSPOSE', 'NON-UNIT', k-1, b, ldb,a( k, 1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_saxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ssyr2( uplo, k-1, one, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_saxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_sscal( k-1, bkk, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_ssygs2
pure module subroutine stdlib${ii}$_dsygs2( itype, uplo, n, a, lda, b, ldb, info )
!! DSYGS2 reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T *A*L.
!! B must have been previously factorized as U**T *U or L*L**T by DPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(dp), intent(inout) :: a(lda,*)
real(dp), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(dp) :: akk, bkk, ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSYGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_dscal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_daxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_dsyr2( uplo, n-k, -one, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_daxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_dtrsv( uplo, 'TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), ldb, &
a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_dscal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_daxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_dsyr2( uplo, n-k, -one, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1, &
k+1 ), lda )
call stdlib${ii}$_daxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_dtrsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_dtrmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_daxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_dsyr2( uplo, k-1, one, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_daxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_dscal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_dtrmv( uplo, 'TRANSPOSE', 'NON-UNIT', k-1, b, ldb,a( k, 1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_daxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dsyr2( uplo, k-1, one, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_daxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_dscal( k-1, bkk, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_dsygs2
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$sygs2( itype, uplo, n, a, lda, b, ldb, info )
!! DSYGS2: reduces a real symmetric-definite generalized eigenproblem
!! to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T *A*L.
!! B must have been previously factorized as U**T *U or L*L**T by DPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
real(${rk}$), intent(inout) :: a(lda,*)
real(${rk}$), intent(in) :: b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(${rk}$) :: akk, bkk, ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSYGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_${ri}$scal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_${ri}$axpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_${ri}$syr2( uplo, n-k, -one, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_${ri}$axpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_${ri}$trsv( uplo, 'TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), ldb, &
a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**t)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = a( k, k )
bkk = b( k, k )
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_${ri}$scal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_${ri}$axpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_${ri}$syr2( uplo, n-k, -one, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1, &
k+1 ), lda )
call stdlib${ii}$_${ri}$axpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_${ri}$trsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**t
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_${ri}$trmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_${ri}$axpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_${ri}$syr2( uplo, k-1, one, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_${ri}$axpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_${ri}$scal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = a( k, k )
bkk = b( k, k )
call stdlib${ii}$_${ri}$trmv( uplo, 'TRANSPOSE', 'NON-UNIT', k-1, b, ldb,a( k, 1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_${ri}$axpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$syr2( uplo, k-1, one, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_${ri}$axpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ri}$scal( k-1, bkk, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_${ri}$sygs2
#:endif
#:endfor
pure module subroutine stdlib${ii}$_sspgst( itype, uplo, n, ap, bp, info )
!! SSPGST reduces a real symmetric-definite generalized eigenproblem
!! to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by SPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
real(sp), intent(inout) :: ap(*)
real(sp), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(sp) :: ajj, akk, bjj, bkk, ct
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
bjj = bp( jj )
call stdlib${ii}$_stpsv( uplo, 'TRANSPOSE', 'NONUNIT', j, bp,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_sspmv( uplo, j-1, -one, ap, bp( j1 ), 1_${ik}$, one,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_sscal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_sdot( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**t)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = ap( kk )
bkk = bp( kk )
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_sscal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_saxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_sspr2( uplo, n-k, -one, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 )&
)
call stdlib${ii}$_saxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_stpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**t
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = ap( kk )
bkk = bp( kk )
call stdlib${ii}$_stpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_saxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_sspr2( uplo, k-1, one, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_saxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_sscal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = ap( jj )
bjj = bp( jj )
ap( jj ) = ajj*bjj + stdlib${ii}$_sdot( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_sscal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_sspmv( uplo, n-j, one, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,one, ap( jj+1 ), &
1_${ik}$ )
call stdlib${ii}$_stpmv( uplo, 'TRANSPOSE', 'NON-UNIT', n-j+1,bp( jj ), ap( jj ), 1_${ik}$ &
)
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_sspgst
pure module subroutine stdlib${ii}$_dspgst( itype, uplo, n, ap, bp, info )
!! DSPGST reduces a real symmetric-definite generalized eigenproblem
!! to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by DPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
real(dp), intent(inout) :: ap(*)
real(dp), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(dp) :: ajj, akk, bjj, bkk, ct
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
bjj = bp( jj )
call stdlib${ii}$_dtpsv( uplo, 'TRANSPOSE', 'NONUNIT', j, bp,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_dspmv( uplo, j-1, -one, ap, bp( j1 ), 1_${ik}$, one,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_dscal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_ddot( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**t)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = ap( kk )
bkk = bp( kk )
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_dscal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_daxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_dspr2( uplo, n-k, -one, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 )&
)
call stdlib${ii}$_daxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_dtpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**t
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = ap( kk )
bkk = bp( kk )
call stdlib${ii}$_dtpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_daxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_dspr2( uplo, k-1, one, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_daxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_dscal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = ap( jj )
bjj = bp( jj )
ap( jj ) = ajj*bjj + stdlib${ii}$_ddot( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_dscal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_dspmv( uplo, n-j, one, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,one, ap( jj+1 ), &
1_${ik}$ )
call stdlib${ii}$_dtpmv( uplo, 'TRANSPOSE', 'NON-UNIT', n-j+1,bp( jj ), ap( jj ), 1_${ik}$ &
)
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_dspgst
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$spgst( itype, uplo, n, ap, bp, info )
!! DSPGST: reduces a real symmetric-definite generalized eigenproblem
!! to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**T)*A*inv(U) or inv(L)*A*inv(L**T)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**T or L**T*A*L.
!! B must have been previously factorized as U**T*U or L*L**T by DPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
real(${rk}$), intent(inout) :: ap(*)
real(${rk}$), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(${rk}$) :: ajj, akk, bjj, bkk, ct
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**t)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
bjj = bp( jj )
call stdlib${ii}$_${ri}$tpsv( uplo, 'TRANSPOSE', 'NONUNIT', j, bp,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$spmv( uplo, j-1, -one, ap, bp( j1 ), 1_${ik}$, one,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$scal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_${ri}$dot( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**t)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = ap( kk )
bkk = bp( kk )
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_${ri}$scal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_${ri}$axpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$spr2( uplo, n-k, -one, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 )&
)
call stdlib${ii}$_${ri}$axpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$tpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**t
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = ap( kk )
bkk = bp( kk )
call stdlib${ii}$_${ri}$tpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_${ri}$axpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$spr2( uplo, k-1, one, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_${ri}$axpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$scal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**t *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = ap( jj )
bjj = bp( jj )
ap( jj ) = ajj*bjj + stdlib${ii}$_${ri}$dot( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$scal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$spmv( uplo, n-j, one, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,one, ap( jj+1 ), &
1_${ik}$ )
call stdlib${ii}$_${ri}$tpmv( uplo, 'TRANSPOSE', 'NON-UNIT', n-j+1,bp( jj ), ap( jj ), 1_${ik}$ &
)
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_${ri}$spgst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_ssbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, info )
!! SSBGST reduces a real symmetric-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**T*S by SPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**T*A*X, where
!! X = S**(-1)*Q and Q is an orthogonal matrix chosen to preserve the
!! bandwidth of A.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(sp), intent(inout) :: ab(ldab,*)
real(sp), intent(in) :: bb(ldbb,*)
real(sp), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(sp) :: bii, ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_slaset( 'FULL', n, n, zero, one, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_spbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**t*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**t*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the cosines and sines of the rotations are stored in the array
! work. the cosines of the 1st set of rotations are stored in
! elements n+2:n+m-kb-1 and the sines of the 1st set in elements
! 2:m-kb-1; the cosines of the 2nd set are stored in elements
! n+m-kb+1:2*n and the sines of the second set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*ab( k-i+ka1, i ) -bb(&
k-i+kb1, i )*ab( j-i+ka1, i ) +ab( ka1, i )*bb( j-i+kb1, i )*bb( k-i+kb1, &
i )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( k-i+kb1, i )*ab( j-i+ka1, i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_sscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_sger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i ), &
1_${ik}$, x( m+1, i-kbt ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_slartg( ab( k+1, i-k+ka ), ra1,work( n+i-k+ka-m ), work( i-k+&
ka-m ),ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_slargv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,work( &
n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2-m ),work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_srot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, work( n+j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,work( n+j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2 ),work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_srot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*ab( i-k+1, k ) -bb( i-k+1, &
k )*ab( i-j+1, j ) +ab( 1_${ik}$, i )*bb( i-j+1, j )*bb( i-k+1, k )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-k+1, k )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_sscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_sger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-kbt )&
, ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_slartg( ab( ka1-k, i ), ra1, work( n+i-k+ka-m ),work( i-k+ka-m &
), ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_slargv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
work( n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2-m ), work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_srot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,work( n+j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,work( n+j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2 ), work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_srot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i1, i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*ab( i-k+ka1, k ) -bb(&
i-k+kb1, k )*ab( i-j+ka1, j ) +ab( ka1, i )*bb( i-j+kb1, j )*bb( i-k+kb1, &
k )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-k+kb1, k )*ab( i-j+ka1, j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_sscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_sger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( kb, i+1 ),ldbb-&
1_${ik}$, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_slartg( ab( k+1, i ), ra1, work( n+i+k-ka ),work( i+k-ka ), ra &
)
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_slargv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,work( &
n+j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_srot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca,&
work( n+m-kb+j1 ), work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_srot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i1, i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*ab( k-i+1, i ) -bb( k-i+1, &
i )*ab( j-i+1, i ) +ab( 1_${ik}$, i )*bb( j-i+1, i )*bb( k-i+1, i )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( k-i+1, i )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_sscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_sger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ), 1_${ik}$,x( 1_${ik}$, &
i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_slartg( ab( ka1-k, i+k-ka ), ra1,work( n+i+k-ka ), work( i+k-&
ka ), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( ka1, i+k-ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_slargv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,work( n+&
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_srot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_slartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_slar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_srot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_ssbgst
pure module subroutine stdlib${ii}$_dsbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, info )
!! DSBGST reduces a real symmetric-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**T*S by DPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**T*A*X, where
!! X = S**(-1)*Q and Q is an orthogonal matrix chosen to preserve the
!! bandwidth of A.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(dp), intent(inout) :: ab(ldab,*)
real(dp), intent(in) :: bb(ldbb,*)
real(dp), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(dp) :: bii, ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_dlaset( 'FULL', n, n, zero, one, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_dpbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**t*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**t*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the cosines and sines of the rotations are stored in the array
! work. the cosines of the 1st set of rotations are stored in
! elements n+2:n+m-kb-1 and the sines of the 1st set in elements
! 2:m-kb-1; the cosines of the 2nd set are stored in elements
! n+m-kb+1:2*n and the sines of the second set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*ab( k-i+ka1, i ) -bb(&
k-i+kb1, i )*ab( j-i+ka1, i ) +ab( ka1, i )*bb( j-i+kb1, i )*bb( k-i+kb1, &
i )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( k-i+kb1, i )*ab( j-i+ka1, i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_dscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_dger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i ), &
1_${ik}$, x( m+1, i-kbt ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_dlartg( ab( k+1, i-k+ka ), ra1,work( n+i-k+ka-m ), work( i-k+&
ka-m ),ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_dlargv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,work( &
n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2-m ),work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_drot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, work( n+j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,work( n+j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2 ),work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_drot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*ab( i-k+1, k ) -bb( i-k+1, &
k )*ab( i-j+1, j ) +ab( 1_${ik}$, i )*bb( i-j+1, j )*bb( i-k+1, k )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-k+1, k )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_dscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_dger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-kbt )&
, ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_dlartg( ab( ka1-k, i ), ra1, work( n+i-k+ka-m ),work( i-k+ka-m &
), ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_dlargv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
work( n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2-m ), work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_drot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,work( n+j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,work( n+j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2 ), work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_drot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i1, i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*ab( i-k+ka1, k ) -bb(&
i-k+kb1, k )*ab( i-j+ka1, j ) +ab( ka1, i )*bb( i-j+kb1, j )*bb( i-k+kb1, &
k )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-k+kb1, k )*ab( i-j+ka1, j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_dscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_dger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( kb, i+1 ),ldbb-&
1_${ik}$, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_dlartg( ab( k+1, i ), ra1, work( n+i+k-ka ),work( i+k-ka ), ra &
)
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_dlargv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,work( &
n+j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_drot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca,&
work( n+m-kb+j1 ), work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_drot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i1, i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*ab( k-i+1, i ) -bb( k-i+1, &
i )*ab( j-i+1, i ) +ab( 1_${ik}$, i )*bb( j-i+1, i )*bb( k-i+1, i )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( k-i+1, i )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_dscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_dger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ), 1_${ik}$,x( 1_${ik}$, &
i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_dlartg( ab( ka1-k, i+k-ka ), ra1,work( n+i+k-ka ), work( i+k-&
ka ), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( ka1, i+k-ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_dlargv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,work( n+&
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_drot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_dlartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_dlar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_drot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_dsbgst
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$sbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, info )
!! DSBGST: reduces a real symmetric-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**T*S by DPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**T*A*X, where
!! X = S**(-1)*Q and Q is an orthogonal matrix chosen to preserve the
!! bandwidth of A.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(${rk}$), intent(inout) :: ab(ldab,*)
real(${rk}$), intent(in) :: bb(ldbb,*)
real(${rk}$), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(${rk}$) :: bii, ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_${ri}$laset( 'FULL', n, n, zero, one, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_${ri}$pbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**t*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**t*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the cosines and sines of the rotations are stored in the array
! work. the cosines of the 1st set of rotations are stored in
! elements n+2:n+m-kb-1 and the sines of the 1st set in elements
! 2:m-kb-1; the cosines of the 2nd set are stored in elements
! n+m-kb+1:2*n and the sines of the second set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*ab( k-i+ka1, i ) -bb(&
k-i+kb1, i )*ab( j-i+ka1, i ) +ab( ka1, i )*bb( j-i+kb1, i )*bb( k-i+kb1, &
i )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( k-i+kb1, i )*ab( j-i+ka1, i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ri}$scal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ri}$ger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i ), &
1_${ik}$, x( m+1, i-kbt ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_${ri}$lartg( ab( k+1, i-k+ka ), ra1,work( n+i-k+ka-m ), work( i-k+&
ka-m ),ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$largv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,work( &
n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2-m ),work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_${ri}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, work( n+j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = work( n+j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,work( n+j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, work(&
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
work( n+j2 ),work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_${ri}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca,work( n+j2-m ), work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*ab( i-k+1, k ) -bb( i-k+1, &
k )*ab( i-j+1, j ) +ab( 1_${ik}$, i )*bb( i-j+1, j )*bb( i-k+1, k )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-k+1, k )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ri}$scal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ri}$ger( n-m, kbt, -one, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-kbt )&
, ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_${ri}$lartg( ab( ka1-k, i ), ra1, work( n+i-k+ka-m ),work( i-k+ka-m &
), ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = work( n+i-k+ka-m )*t -work( i-k+ka-m )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +work( n+i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$largv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
work( n+j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2-m ), work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_${ri}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j-m ), &
work( j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,work( n+j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
work( n+j ) = work( n+j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = work( n+j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,work( n+j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, work( &
n+j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, work( n+&
j2 ), work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_${ri}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,work( n+j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, work( n+j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, i - kb + 2*ka + 1, -1
work( n+j-m ) = work( n+j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( kb1, i )
do j = i1, i
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*ab( i-k+ka1, k ) -bb(&
i-k+kb1, k )*ab( i-j+ka1, j ) +ab( ka1, i )*bb( i-j+kb1, j )*bb( i-k+kb1, &
k )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-k+kb1, k )*ab( i-j+ka1, j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ri}$scal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ri}$ger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( kb, i+1 ),ldbb-&
1_${ik}$, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_${ri}$lartg( ab( k+1, i ), ra1, work( n+i+k-ka ),work( i+k-ka ), ra &
)
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$largv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,work( &
n+j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_${ri}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = work( n+m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca,&
work( n+m-kb+j1 ), work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
work( n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_${ri}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
work( n+j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**t * a * inv(s(i))
bii = bb( 1_${ik}$, i )
do j = i1, i
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*ab( k-i+1, i ) -bb( k-i+1, &
i )*ab( j-i+1, i ) +ab( 1_${ik}$, i )*bb( j-i+1, i )*bb( k-i+1, i )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( k-i+1, i )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ri}$scal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ri}$ger( nx, kbt, -one, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ), 1_${ik}$,x( 1_${ik}$, &
i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_${ri}$lartg( ab( ka1-k, i+k-ka ), ra1,work( n+i+k-ka ), work( i+k-&
ka ), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = work( n+i+k-ka )*t -work( i+k-ka )*ab( ka1, i+k-ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +work( n+i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$largv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,work( n+&
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+j1 ),work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_${ri}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+j ), work( j ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,work( n+m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
work( n+m-kb+j ) = work( n+m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = work( n+m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, work( n+m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, work( n+&
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ri}$lar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, work( &
n+m-kb+j1 ),work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_${ri}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,work( n+m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,work( n+j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, min( i+kb, m ) - 2*ka - 1
work( n+j ) = work( n+j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_${ri}$sbgst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chegst( itype, uplo, n, a, lda, b, ldb, info )
!! CHEGST reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by CPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(sp), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHEGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'CHEGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_chegs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_chegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_ctrsm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, &
n-k-kb+1, cone,b( k, k ), ldb, a( k, k+kb ), lda )
call stdlib${ii}$_chemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_cher2k( uplo, 'CONJUGATE TRANSPOSE', n-k-kb+1,kb, -cone, a( &
k, k+kb ), lda,b( k, k+kb ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_chemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_ctrsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, cone,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_chegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_ctrsm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', n-k-&
kb+1, kb, cone,b( k, k ), ldb, a( k+kb, k ), lda )
call stdlib${ii}$_chemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_cher2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-cone, a( k+kb, &
k ), lda,b( k+kb, k ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_chemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_ctrsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, cone,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_ctrmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, cone, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_chemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_cher2k( uplo, 'NO TRANSPOSE', k-1, kb, cone,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_chemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_ctrmm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', k-1, &
kb, cone, b( k, k ), ldb,a( 1_${ik}$, k ), lda )
call stdlib${ii}$_chegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**h*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_ctrmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, cone,&
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_chemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_cher2k( uplo, 'CONJUGATE TRANSPOSE', k-1, kb,cone, a( k, 1_${ik}$ ), &
lda, b( k, 1_${ik}$ ), ldb,one, a, lda )
call stdlib${ii}$_chemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_ctrmm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, k-1,&
cone, b( k, k ), ldb,a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_chegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_chegst
pure module subroutine stdlib${ii}$_zhegst( itype, uplo, n, a, lda, b, ldb, info )
!! ZHEGST reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by ZPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(dp), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHEGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'ZHEGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_zhegs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_zhegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_ztrsm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, &
n-k-kb+1, cone,b( k, k ), ldb, a( k, k+kb ), lda )
call stdlib${ii}$_zhemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_zher2k( uplo, 'CONJUGATE TRANSPOSE', n-k-kb+1,kb, -cone, a( &
k, k+kb ), lda,b( k, k+kb ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_zhemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_ztrsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, cone,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_zhegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_ztrsm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', n-k-&
kb+1, kb, cone,b( k, k ), ldb, a( k+kb, k ), lda )
call stdlib${ii}$_zhemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_zher2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-cone, a( k+kb, &
k ), lda,b( k+kb, k ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_zhemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_ztrsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, cone,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_ztrmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, cone, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_zhemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_zher2k( uplo, 'NO TRANSPOSE', k-1, kb, cone,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_zhemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_ztrmm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', k-1, &
kb, cone, b( k, k ), ldb,a( 1_${ik}$, k ), lda )
call stdlib${ii}$_zhegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**h*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_ztrmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, cone,&
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_zhemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_zher2k( uplo, 'CONJUGATE TRANSPOSE', k-1, kb,cone, a( k, 1_${ik}$ ), &
lda, b( k, 1_${ik}$ ), ldb,one, a, lda )
call stdlib${ii}$_zhemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_ztrmm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, k-1,&
cone, b( k, k ), ldb,a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_zhegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_zhegst
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hegst( itype, uplo, n, a, lda, b, ldb, info )
!! ZHEGST: reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by ZPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(${ck}$), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k, kb, nb
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHEGST', -info )
return
end if
! quick return if possible
if( n==0 )return
! determine the block size for this environment.
nb = stdlib${ii}$_ilaenv( 1_${ik}$, 'ZHEGST', uplo, n, -1_${ik}$, -1_${ik}$, -1_${ik}$ )
if( nb<=1_${ik}$ .or. nb>=n ) then
! use unblocked code
call stdlib${ii}$_${ci}$hegs2( itype, uplo, n, a, lda, b, ldb, info )
else
! use blocked code
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(k:n,k:n)
call stdlib${ii}$_${ci}$hegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_${ci}$trsm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, &
n-k-kb+1, cone,b( k, k ), ldb, a( k, k+kb ), lda )
call stdlib${ii}$_${ci}$hemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_${ci}$her2k( uplo, 'CONJUGATE TRANSPOSE', n-k-kb+1,kb, -cone, a( &
k, k+kb ), lda,b( k, k+kb ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_${ci}$hemm( 'LEFT', uplo, kb, n-k-kb+1, -chalf,a( k, k ), lda, b(&
k, k+kb ), ldb,cone, a( k, k+kb ), lda )
call stdlib${ii}$_${ci}$trsm( 'RIGHT', uplo, 'NO TRANSPOSE','NON-UNIT', kb, n-k-kb+&
1_${ik}$, cone,b( k+kb, k+kb ), ldb, a( k, k+kb ),lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(k:n,k:n)
call stdlib${ii}$_${ci}$hegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
if( k+kb<=n ) then
call stdlib${ii}$_${ci}$trsm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', n-k-&
kb+1, kb, cone,b( k, k ), ldb, a( k+kb, k ), lda )
call stdlib${ii}$_${ci}$hemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_${ci}$her2k( uplo, 'NO TRANSPOSE', n-k-kb+1, kb,-cone, a( k+kb, &
k ), lda,b( k+kb, k ), ldb, one,a( k+kb, k+kb ), lda )
call stdlib${ii}$_${ci}$hemm( 'RIGHT', uplo, n-k-kb+1, kb, -chalf,a( k, k ), lda, &
b( k+kb, k ), ldb,cone, a( k+kb, k ), lda )
call stdlib${ii}$_${ci}$trsm( 'LEFT', uplo, 'NO TRANSPOSE','NON-UNIT', n-k-kb+1, &
kb, cone,b( k+kb, k+kb ), ldb, a( k+kb, k ),lda )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the upper triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_${ci}$trmm( 'LEFT', uplo, 'NO TRANSPOSE', 'NON-UNIT',k-1, kb, cone, &
b, ldb, a( 1_${ik}$, k ), lda )
call stdlib${ii}$_${ci}$hemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_${ci}$her2k( uplo, 'NO TRANSPOSE', k-1, kb, cone,a( 1_${ik}$, k ), lda, b( &
1_${ik}$, k ), ldb, one, a,lda )
call stdlib${ii}$_${ci}$hemm( 'RIGHT', uplo, k-1, kb, chalf, a( k, k ),lda, b( 1_${ik}$, k ),&
ldb, cone, a( 1_${ik}$, k ),lda )
call stdlib${ii}$_${ci}$trmm( 'RIGHT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', k-1, &
kb, cone, b( k, k ), ldb,a( 1_${ik}$, k ), lda )
call stdlib${ii}$_${ci}$hegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
else
! compute l**h*a*l
do k = 1, n, nb
kb = min( n-k+1, nb )
! update the lower triangle of a(1:k+kb-1,1:k+kb-1)
call stdlib${ii}$_${ci}$trmm( 'RIGHT', uplo, 'NO TRANSPOSE', 'NON-UNIT',kb, k-1, cone,&
b, ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$hemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_${ci}$her2k( uplo, 'CONJUGATE TRANSPOSE', k-1, kb,cone, a( k, 1_${ik}$ ), &
lda, b( k, 1_${ik}$ ), ldb,one, a, lda )
call stdlib${ii}$_${ci}$hemm( 'LEFT', uplo, kb, k-1, chalf, a( k, k ),lda, b( k, 1_${ik}$ ), &
ldb, cone, a( k, 1_${ik}$ ),lda )
call stdlib${ii}$_${ci}$trmm( 'LEFT', uplo, 'CONJUGATE TRANSPOSE','NON-UNIT', kb, k-1,&
cone, b( k, k ), ldb,a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$hegs2( itype, uplo, kb, a( k, k ), lda,b( k, k ), ldb, info )
end do
end if
end if
end if
return
end subroutine stdlib${ii}$_${ci}$hegst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chegs2( itype, uplo, n, a, lda, b, ldb, info )
!! CHEGS2 reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H *A*L.
!! B must have been previously factorized as U**H *U or L*L**H by ZPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(sp), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(sp) :: akk, bkk
complex(sp) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHEGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=sp)
bkk = real( b( k, k ),KIND=sp)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_csscal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_clacgv( n-k, a( k, k+1 ), lda )
call stdlib${ii}$_clacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_caxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_cher2( uplo, n-k, -cone, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_caxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_clacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_ctrsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-k, b( k+1, k+&
1_${ik}$ ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_clacgv( n-k, a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=sp)
bkk = real( b( k, k ),KIND=sp)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_csscal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_caxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_cher2( uplo, n-k, -cone, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1,&
k+1 ), lda )
call stdlib${ii}$_caxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_ctrsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=sp)
bkk = real( b( k, k ),KIND=sp)
call stdlib${ii}$_ctrmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_caxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_cher2( uplo, k-1, cone, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_caxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_csscal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=sp)
bkk = real( b( k, k ),KIND=sp)
call stdlib${ii}$_clacgv( k-1, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ctrmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', k-1,b, ldb, a( k, &
1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_clacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_caxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_cher2( uplo, k-1, cone, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_caxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_clacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_csscal( k-1, bkk, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_clacgv( k-1, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_chegs2
pure module subroutine stdlib${ii}$_zhegs2( itype, uplo, n, a, lda, b, ldb, info )
!! ZHEGS2 reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H *A*L.
!! B must have been previously factorized as U**H *U or L*L**H by ZPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(dp), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(dp) :: akk, bkk
complex(dp) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHEGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=dp)
bkk = real( b( k, k ),KIND=dp)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_zdscal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_zlacgv( n-k, a( k, k+1 ), lda )
call stdlib${ii}$_zlacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_zaxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_zher2( uplo, n-k, -cone, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_zaxpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_zlacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_ztrsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-k, b( k+1, k+&
1_${ik}$ ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_zlacgv( n-k, a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=dp)
bkk = real( b( k, k ),KIND=dp)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_zdscal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_zaxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_zher2( uplo, n-k, -cone, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1,&
k+1 ), lda )
call stdlib${ii}$_zaxpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_ztrsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=dp)
bkk = real( b( k, k ),KIND=dp)
call stdlib${ii}$_ztrmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_zaxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_zher2( uplo, k-1, cone, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_zaxpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_zdscal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=dp)
bkk = real( b( k, k ),KIND=dp)
call stdlib${ii}$_zlacgv( k-1, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_ztrmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', k-1,b, ldb, a( k, &
1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_zlacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_zaxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_zher2( uplo, k-1, cone, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_zaxpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_zlacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_zdscal( k-1, bkk, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_zlacgv( k-1, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_zhegs2
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hegs2( itype, uplo, n, a, lda, b, ldb, info )
!! ZHEGS2: reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H *A*L.
!! B must have been previously factorized as U**H *U or L*L**H by ZPOTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, lda, ldb, n
! Array Arguments
complex(${ck}$), intent(inout) :: a(lda,*), b(ldb,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: k
real(${ck}$) :: akk, bkk
complex(${ck}$) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( lda<max( 1_${ik}$, n ) ) then
info = -5_${ik}$
else if( ldb<max( 1_${ik}$, n ) ) then
info = -7_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHEGS2', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
do k = 1, n
! update the upper triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=${ck}$)
bkk = real( b( k, k ),KIND=${ck}$)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_${ci}$dscal( n-k, one / bkk, a( k, k+1 ), lda )
ct = -half*akk
call stdlib${ii}$_${ci}$lacgv( n-k, a( k, k+1 ), lda )
call stdlib${ii}$_${ci}$lacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_${ci}$axpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_${ci}$her2( uplo, n-k, -cone, a( k, k+1 ), lda,b( k, k+1 ), ldb, a( &
k+1, k+1 ), lda )
call stdlib${ii}$_${ci}$axpy( n-k, ct, b( k, k+1 ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_${ci}$lacgv( n-k, b( k, k+1 ), ldb )
call stdlib${ii}$_${ci}$trsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-k, b( k+1, k+&
1_${ik}$ ), ldb, a( k, k+1 ),lda )
call stdlib${ii}$_${ci}$lacgv( n-k, a( k, k+1 ), lda )
end if
end do
else
! compute inv(l)*a*inv(l**h)
do k = 1, n
! update the lower triangle of a(k:n,k:n)
akk = real( a( k, k ),KIND=${ck}$)
bkk = real( b( k, k ),KIND=${ck}$)
akk = akk / bkk**2_${ik}$
a( k, k ) = akk
if( k<n ) then
call stdlib${ii}$_${ci}$dscal( n-k, one / bkk, a( k+1, k ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_${ci}$axpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_${ci}$her2( uplo, n-k, -cone, a( k+1, k ), 1_${ik}$,b( k+1, k ), 1_${ik}$, a( k+1,&
k+1 ), lda )
call stdlib${ii}$_${ci}$axpy( n-k, ct, b( k+1, k ), 1_${ik}$, a( k+1, k ), 1_${ik}$ )
call stdlib${ii}$_${ci}$trsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,b( k+1, k+1 ), &
ldb, a( k+1, k ), 1_${ik}$ )
end if
end do
end if
else
if( upper ) then
! compute u*a*u**h
do k = 1, n
! update the upper triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=${ck}$)
bkk = real( b( k, k ),KIND=${ck}$)
call stdlib${ii}$_${ci}$trmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, b,ldb, a( 1_${ik}$, k ), 1_${ik}$ &
)
ct = half*akk
call stdlib${ii}$_${ci}$axpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_${ci}$her2( uplo, k-1, cone, a( 1_${ik}$, k ), 1_${ik}$, b( 1_${ik}$, k ), 1_${ik}$,a, lda )
call stdlib${ii}$_${ci}$axpy( k-1, ct, b( 1_${ik}$, k ), 1_${ik}$, a( 1_${ik}$, k ), 1_${ik}$ )
call stdlib${ii}$_${ci}$dscal( k-1, bkk, a( 1_${ik}$, k ), 1_${ik}$ )
a( k, k ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
do k = 1, n
! update the lower triangle of a(1:k,1:k)
akk = real( a( k, k ),KIND=${ck}$)
bkk = real( b( k, k ),KIND=${ck}$)
call stdlib${ii}$_${ci}$lacgv( k-1, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$trmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', k-1,b, ldb, a( k, &
1_${ik}$ ), lda )
ct = half*akk
call stdlib${ii}$_${ci}$lacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_${ci}$axpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$her2( uplo, k-1, cone, a( k, 1_${ik}$ ), lda, b( k, 1_${ik}$ ),ldb, a, lda )
call stdlib${ii}$_${ci}$axpy( k-1, ct, b( k, 1_${ik}$ ), ldb, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$lacgv( k-1, b( k, 1_${ik}$ ), ldb )
call stdlib${ii}$_${ci}$dscal( k-1, bkk, a( k, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$lacgv( k-1, a( k, 1_${ik}$ ), lda )
a( k, k ) = akk*bkk**2_${ik}$
end do
end if
end if
return
end subroutine stdlib${ii}$_${ci}$hegs2
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chpgst( itype, uplo, n, ap, bp, info )
!! CHPGST reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by CPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
complex(sp), intent(inout) :: ap(*)
complex(sp), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(sp) :: ajj, akk, bjj, bkk
complex(sp) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
ap( jj ) = real( ap( jj ),KIND=sp)
bjj = real( bp( jj ),KIND=sp)
call stdlib${ii}$_ctpsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', j,bp, ap( j1 ), 1_${ik}$ &
)
call stdlib${ii}$_chpmv( uplo, j-1, -cone, ap, bp( j1 ), 1_${ik}$, cone,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_csscal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_cdotc( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**h)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = real( ap( kk ),KIND=sp)
bkk = real( bp( kk ),KIND=sp)
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_csscal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_caxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_chpr2( uplo, n-k, -cone, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 &
) )
call stdlib${ii}$_caxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_ctpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**h
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = real( ap( kk ),KIND=sp)
bkk = real( bp( kk ),KIND=sp)
call stdlib${ii}$_ctpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_caxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_chpr2( uplo, k-1, cone, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_caxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_csscal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = real( ap( jj ),KIND=sp)
bjj = real( bp( jj ),KIND=sp)
ap( jj ) = ajj*bjj + stdlib${ii}$_cdotc( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_csscal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_chpmv( uplo, n-j, cone, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,cone, ap( jj+1 )&
, 1_${ik}$ )
call stdlib${ii}$_ctpmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-j+1, bp( jj ), &
ap( jj ), 1_${ik}$ )
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_chpgst
pure module subroutine stdlib${ii}$_zhpgst( itype, uplo, n, ap, bp, info )
!! ZHPGST reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by ZPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
complex(dp), intent(inout) :: ap(*)
complex(dp), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(dp) :: ajj, akk, bjj, bkk
complex(dp) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
ap( jj ) = real( ap( jj ),KIND=dp)
bjj = real( bp( jj ),KIND=dp)
call stdlib${ii}$_ztpsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', j,bp, ap( j1 ), 1_${ik}$ &
)
call stdlib${ii}$_zhpmv( uplo, j-1, -cone, ap, bp( j1 ), 1_${ik}$, cone,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_zdscal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_zdotc( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**h)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = real( ap( kk ),KIND=dp)
bkk = real( bp( kk ),KIND=dp)
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_zdscal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_zaxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_zhpr2( uplo, n-k, -cone, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 &
) )
call stdlib${ii}$_zaxpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_ztpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**h
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = real( ap( kk ),KIND=dp)
bkk = real( bp( kk ),KIND=dp)
call stdlib${ii}$_ztpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_zaxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_zhpr2( uplo, k-1, cone, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_zaxpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_zdscal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = real( ap( jj ),KIND=dp)
bjj = real( bp( jj ),KIND=dp)
ap( jj ) = ajj*bjj + stdlib${ii}$_zdotc( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_zdscal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_zhpmv( uplo, n-j, cone, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,cone, ap( jj+1 )&
, 1_${ik}$ )
call stdlib${ii}$_ztpmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-j+1, bp( jj ), &
ap( jj ), 1_${ik}$ )
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_zhpgst
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hpgst( itype, uplo, n, ap, bp, info )
!! ZHPGST: reduces a complex Hermitian-definite generalized
!! eigenproblem to standard form, using packed storage.
!! If ITYPE = 1, the problem is A*x = lambda*B*x,
!! and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)
!! If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
!! B*A*x = lambda*x, and A is overwritten by U*A*U**H or L**H*A*L.
!! B must have been previously factorized as U**H*U or L*L**H by ZPPTRF.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: itype, n
! Array Arguments
complex(${ck}$), intent(inout) :: ap(*)
complex(${ck}$), intent(in) :: bp(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, j1, j1j1, jj, k, k1, k1k1, kk
real(${ck}$) :: ajj, akk, bjj, bkk
complex(${ck}$) :: ct
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( itype<1_${ik}$ .or. itype>3_${ik}$ ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHPGST', -info )
return
end if
if( itype==1_${ik}$ ) then
if( upper ) then
! compute inv(u**h)*a*inv(u)
! j1 and jj are the indices of a(1,j) and a(j,j)
jj = 0_${ik}$
do j = 1, n
j1 = jj + 1_${ik}$
jj = jj + j
! compute the j-th column of the upper triangle of a
ap( jj ) = real( ap( jj ),KIND=${ck}$)
bjj = real( bp( jj ),KIND=${ck}$)
call stdlib${ii}$_${ci}$tpsv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT', j,bp, ap( j1 ), 1_${ik}$ &
)
call stdlib${ii}$_${ci}$hpmv( uplo, j-1, -cone, ap, bp( j1 ), 1_${ik}$, cone,ap( j1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$dscal( j-1, one / bjj, ap( j1 ), 1_${ik}$ )
ap( jj ) = ( ap( jj )-stdlib${ii}$_${ci}$dotc( j-1, ap( j1 ), 1_${ik}$, bp( j1 ),1_${ik}$ ) ) / &
bjj
end do
else
! compute inv(l)*a*inv(l**h)
! kk and k1k1 are the indices of a(k,k) and a(k+1,k+1)
kk = 1_${ik}$
do k = 1, n
k1k1 = kk + n - k + 1_${ik}$
! update the lower triangle of a(k:n,k:n)
akk = real( ap( kk ),KIND=${ck}$)
bkk = real( bp( kk ),KIND=${ck}$)
akk = akk / bkk**2_${ik}$
ap( kk ) = akk
if( k<n ) then
call stdlib${ii}$_${ci}$dscal( n-k, one / bkk, ap( kk+1 ), 1_${ik}$ )
ct = -half*akk
call stdlib${ii}$_${ci}$axpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$hpr2( uplo, n-k, -cone, ap( kk+1 ), 1_${ik}$,bp( kk+1 ), 1_${ik}$, ap( k1k1 &
) )
call stdlib${ii}$_${ci}$axpy( n-k, ct, bp( kk+1 ), 1_${ik}$, ap( kk+1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$tpsv( uplo, 'NO TRANSPOSE', 'NON-UNIT', n-k,bp( k1k1 ), ap( &
kk+1 ), 1_${ik}$ )
end if
kk = k1k1
end do
end if
else
if( upper ) then
! compute u*a*u**h
! k1 and kk are the indices of a(1,k) and a(k,k)
kk = 0_${ik}$
do k = 1, n
k1 = kk + 1_${ik}$
kk = kk + k
! update the upper triangle of a(1:k,1:k)
akk = real( ap( kk ),KIND=${ck}$)
bkk = real( bp( kk ),KIND=${ck}$)
call stdlib${ii}$_${ci}$tpmv( uplo, 'NO TRANSPOSE', 'NON-UNIT', k-1, bp,ap( k1 ), 1_${ik}$ )
ct = half*akk
call stdlib${ii}$_${ci}$axpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$hpr2( uplo, k-1, cone, ap( k1 ), 1_${ik}$, bp( k1 ), 1_${ik}$,ap )
call stdlib${ii}$_${ci}$axpy( k-1, ct, bp( k1 ), 1_${ik}$, ap( k1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$dscal( k-1, bkk, ap( k1 ), 1_${ik}$ )
ap( kk ) = akk*bkk**2_${ik}$
end do
else
! compute l**h *a*l
! jj and j1j1 are the indices of a(j,j) and a(j+1,j+1)
jj = 1_${ik}$
do j = 1, n
j1j1 = jj + n - j + 1_${ik}$
! compute the j-th column of the lower triangle of a
ajj = real( ap( jj ),KIND=${ck}$)
bjj = real( bp( jj ),KIND=${ck}$)
ap( jj ) = ajj*bjj + stdlib${ii}$_${ci}$dotc( n-j, ap( jj+1 ), 1_${ik}$,bp( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$dscal( n-j, bjj, ap( jj+1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$hpmv( uplo, n-j, cone, ap( j1j1 ), bp( jj+1 ), 1_${ik}$,cone, ap( jj+1 )&
, 1_${ik}$ )
call stdlib${ii}$_${ci}$tpmv( uplo, 'CONJUGATE TRANSPOSE', 'NON-UNIT',n-j+1, bp( jj ), &
ap( jj ), 1_${ik}$ )
jj = j1j1
end do
end if
end if
return
end subroutine stdlib${ii}$_${ci}$hpgst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, rwork,&
!! CHBGST reduces a complex Hermitian-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**H*S by CPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**H*A*X, where
!! X = S**(-1)*Q and Q is a unitary matrix chosen to preserve the
!! bandwidth of A.
info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(sp), intent(out) :: rwork(*)
complex(sp), intent(inout) :: ab(ldab,*)
complex(sp), intent(in) :: bb(ldbb,*)
complex(sp), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(sp) :: bii
complex(sp) :: ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_claset( 'FULL', n, n, czero, cone, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_cpbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**h*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**h*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the real cosines and complex sines of the rotations are stored in
! the arrays rwork and work, those of the 1st set in elements
! 2:m-kb-1, and those of the 2nd set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=sp)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=sp) / bii ) / bii
do j = i + 1, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*conjg( ab( k-i+ka1, &
i ) ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1, i ) +real( ab( ka1, i ),&
KIND=sp)*bb( j-i+kb1, i )*conjg( bb( k-i+kb1, i ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1,&
i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_csscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_cgerc( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i )&
, 1_${ik}$, x( m+1, i-kbt ),ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_clartg( ab( k+1, i-k+ka ), ra1,rwork( i-k+ka-m ), work( i-k+ka-&
m ), ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( 1_${ik}$, i-k+ka &
)
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_clargv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,rwork(&
j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
call stdlib${ii}$_clacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_crot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), &
conjg( work( j-m ) ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, rwork( j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,rwork( j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
call stdlib${ii}$_clacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_crot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), conjg( &
work( j ) ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=sp)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=sp) / bii ) / bii
do j = i + 1, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*conjg( ab( i-k+1,k ) ) - &
conjg( bb( i-k+1, k ) )*ab( i-j+1, j ) + real( ab( 1_${ik}$, i ),KIND=sp)*bb( i-j+&
1_${ik}$, j )*conjg( bb( i-k+1,k ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -conjg( bb( i-k+1, k ) )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_csscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_cgeru( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-&
kbt ), ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_clartg( ab( ka1-k, i ), ra1, rwork( i-k+ka-m ),work( i-k+ka-m )&
, ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_clargv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
rwork( j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2-m ), work( j2-m ), ka1 )
call stdlib${ii}$_clacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_crot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), work(&
j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,rwork( j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,rwork( j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2 ), work( j2 ), ka1 )
call stdlib${ii}$_clacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_crot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=sp)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=sp) / bii ) / bii
do j = i1, i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*conjg( ab( i-k+ka1, &
k ) ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1, j ) +real( ab( ka1, i ),&
KIND=sp)*bb( i-j+kb1, j )*conjg( bb( i-k+kb1, k ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1,&
j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_csscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_cgeru( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$,bb( kb, i+1 ), &
ldbb-1, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_clartg( ab( k+1, i ), ra1, rwork( i+k-ka ),work( i+k-ka ), ra )
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_clargv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( j1 ), work( j1 ),ka1 )
call stdlib${ii}$_clacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_crot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, rwork( m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_clacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_crot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=sp)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=sp) / bii ) / bii
do j = i1, i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*conjg( ab( k-i+1,i ) ) - &
conjg( bb( k-i+1, i ) )*ab( j-i+1, i ) + real( ab( 1_${ik}$, i ),KIND=sp)*bb( j-i+&
1_${ik}$, i )*conjg( bb( k-i+1,i ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -conjg( bb( k-i+1, i ) )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_csscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_cgerc( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ),1_${ik}$, x( &
1_${ik}$, i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_clartg( ab( ka1-k, i+k-ka ), ra1,rwork( i+k-ka ), work( i+k-ka &
), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( ka1, i+k-&
ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_clargv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
j1 ),work( j1 ), ka1 )
call stdlib${ii}$_clacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_crot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), conjg( work(&
j ) ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, rwork( m-kb+&
j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_clartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_clar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_clacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_crot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), conjg( &
work( m-kb+j ) ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_chbgst
pure module subroutine stdlib${ii}$_zhbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, rwork,&
!! ZHBGST reduces a complex Hermitian-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**H*S by ZPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**H*A*X, where
!! X = S**(-1)*Q and Q is a unitary matrix chosen to preserve the
!! bandwidth of A.
info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(dp), intent(out) :: rwork(*)
complex(dp), intent(inout) :: ab(ldab,*)
complex(dp), intent(in) :: bb(ldbb,*)
complex(dp), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(dp) :: bii
complex(dp) :: ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_zlaset( 'FULL', n, n, czero, cone, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_zpbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**h*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**h*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the real cosines and complex sines of the rotations are stored in
! the arrays rwork and work, those of the 1st set in elements
! 2:m-kb-1, and those of the 2nd set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=dp)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=dp) / bii ) / bii
do j = i + 1, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*conjg( ab( k-i+ka1, &
i ) ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1, i ) +real( ab( ka1, i ),&
KIND=dp)*bb( j-i+kb1, i )*conjg( bb( k-i+kb1, i ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1,&
i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_zdscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_zgerc( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i )&
, 1_${ik}$, x( m+1, i-kbt ),ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_zlartg( ab( k+1, i-k+ka ), ra1,rwork( i-k+ka-m ), work( i-k+ka-&
m ), ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( 1_${ik}$, i-k+ka &
)
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_zlargv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,rwork(&
j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_zrot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), &
conjg( work( j-m ) ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, rwork( j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,rwork( j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_zrot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), conjg( &
work( j ) ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=dp)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=dp) / bii ) / bii
do j = i + 1, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*conjg( ab( i-k+1,k ) ) - &
conjg( bb( i-k+1, k ) )*ab( i-j+1, j ) + real( ab( 1_${ik}$, i ),KIND=dp)*bb( i-j+&
1_${ik}$, j )*conjg( bb( i-k+1,k ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -conjg( bb( i-k+1, k ) )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_zdscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_zgeru( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-&
kbt ), ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_zlartg( ab( ka1-k, i ), ra1, rwork( i-k+ka-m ),work( i-k+ka-m )&
, ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_zlargv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
rwork( j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2-m ), work( j2-m ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_zrot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), work(&
j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,rwork( j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,rwork( j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2 ), work( j2 ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_zrot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=dp)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=dp) / bii ) / bii
do j = i1, i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*conjg( ab( i-k+ka1, &
k ) ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1, j ) +real( ab( ka1, i ),&
KIND=dp)*bb( i-j+kb1, j )*conjg( bb( i-k+kb1, k ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1,&
j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_zdscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_zgeru( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$,bb( kb, i+1 ), &
ldbb-1, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_zlartg( ab( k+1, i ), ra1, rwork( i+k-ka ),work( i+k-ka ), ra )
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_zlargv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( j1 ), work( j1 ),ka1 )
call stdlib${ii}$_zlacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_zrot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, rwork( m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_zrot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=dp)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=dp) / bii ) / bii
do j = i1, i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*conjg( ab( k-i+1,i ) ) - &
conjg( bb( k-i+1, i ) )*ab( j-i+1, i ) + real( ab( 1_${ik}$, i ),KIND=dp)*bb( j-i+&
1_${ik}$, i )*conjg( bb( k-i+1,i ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -conjg( bb( k-i+1, i ) )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_zdscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_zgerc( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ),1_${ik}$, x( &
1_${ik}$, i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_zlartg( ab( ka1-k, i+k-ka ), ra1,rwork( i+k-ka ), work( i+k-ka &
), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( ka1, i+k-&
ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_zlargv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
j1 ),work( j1 ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_zrot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), conjg( work(&
j ) ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, rwork( m-kb+&
j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_zlartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_zlar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_zlacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_zrot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), conjg( &
work( m-kb+j ) ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_zhbgst
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hbgst( vect, uplo, n, ka, kb, ab, ldab, bb, ldbb, x,ldx, work, rwork,&
!! ZHBGST: reduces a complex Hermitian-definite banded generalized
!! eigenproblem A*x = lambda*B*x to standard form C*y = lambda*y,
!! such that C has the same bandwidth as A.
!! B must have been previously factorized as S**H*S by ZPBSTF, using a
!! split Cholesky factorization. A is overwritten by C = X**H*A*X, where
!! X = S**(-1)*Q and Q is a unitary matrix chosen to preserve the
!! bandwidth of A.
info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ka, kb, ldab, ldbb, ldx, n
! Array Arguments
real(${ck}$), intent(out) :: rwork(*)
complex(${ck}$), intent(inout) :: ab(ldab,*)
complex(${ck}$), intent(in) :: bb(ldbb,*)
complex(${ck}$), intent(out) :: work(*), x(ldx,*)
! =====================================================================
! Local Scalars
logical(lk) :: update, upper, wantx
integer(${ik}$) :: i, i0, i1, i2, inca, j, j1, j1t, j2, j2t, k, ka1, kb1, kbt, l, m, nr, &
nrt, nx
real(${ck}$) :: bii
complex(${ck}$) :: ra, ra1, t
! Intrinsic Functions
! Executable Statements
! test the input parameters
wantx = stdlib_lsame( vect, 'V' )
upper = stdlib_lsame( uplo, 'U' )
ka1 = ka + 1_${ik}$
kb1 = kb + 1_${ik}$
info = 0_${ik}$
if( .not.wantx .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( ka<0_${ik}$ ) then
info = -4_${ik}$
else if( kb<0_${ik}$ .or. kb>ka ) then
info = -5_${ik}$
else if( ldab<ka+1 ) then
info = -7_${ik}$
else if( ldbb<kb+1 ) then
info = -9_${ik}$
else if( ldx<1_${ik}$ .or. wantx .and. ldx<max( 1_${ik}$, n ) ) then
info = -11_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHBGST', -info )
return
end if
! quick return if possible
if( n==0 )return
inca = ldab*ka1
! initialize x to the unit matrix, if needed
if( wantx )call stdlib${ii}$_${ci}$laset( 'FULL', n, n, czero, cone, x, ldx )
! set m to the splitting point m. it must be the same value as is
! used in stdlib${ii}$_${ci}$pbstf. the chosen value allows the arrays work and rwork
! to be of dimension (n).
m = ( n+kb ) / 2_${ik}$
! the routine works in two phases, corresponding to the two halves
! of the split cholesky factorization of b as s**h*s where
! s = ( u )
! ( m l )
! with u upper triangular of order m, and l lower triangular of
! order n-m. s has the same bandwidth as b.
! s is treated as a product of elementary matrices:
! s = s(m)*s(m-1)*...*s(2)*s(1)*s(m+1)*s(m+2)*...*s(n-1)*s(n)
! where s(i) is determined by the i-th row of s.
! in phase 1, the index i takes the values n, n-1, ... , m+1;
! in phase 2, it takes the values 1, 2, ... , m.
! for each value of i, the current matrix a is updated by forming
! inv(s(i))**h*a*inv(s(i)). this creates a triangular bulge outside
! the band of a. the bulge is then pushed down toward the bottom of
! a in phase 1, and up toward the top of a in phase 2, by applying
! plane rotations.
! there are kb*(kb+1)/2 elements in the bulge, but at most 2*kb-1
! of them are linearly independent, so annihilating a bulge requires
! only 2*kb-1 plane rotations. the rotations are divided into a 1st
! set of kb-1 rotations, and a 2nd set of kb rotations.
! wherever possible, rotations are generated and applied in vector
! operations of length nr between the indices j1 and j2 (sometimes
! replaced by modified values nrt, j1t or j2t).
! the real cosines and complex sines of the rotations are stored in
! the arrays rwork and work, those of the 1st set in elements
! 2:m-kb-1, and those of the 2nd set in elements m-kb+1:n.
! the bulges are not formed explicitly; nonzero elements outside the
! band are created only when they are required for generating new
! rotations; they are stored in the array work, in positions where
! they are later overwritten by the sines of the rotations which
! annihilate them.
! **************************** phase 1 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = n, m + 1, -1
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions downward
! end do
! update = .false.
! do i = m + ka + 1, n - 1
! apply rotations to push all bulges ka positions downward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = n + 1_${ik}$
10 continue
if( update ) then
i = i - 1_${ik}$
kbt = min( kb, i-1 )
i0 = i - 1_${ik}$
i1 = min( n, i+ka )
i2 = i - kbt + ka1
if( i<m+1 ) then
update = .false.
i = i + 1_${ik}$
i0 = m
if( ka==0 )go to 480
go to 10
end if
else
i = i + ka
if( i>n-1 )go to 480
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=${ck}$)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=${ck}$) / bii ) / bii
do j = i + 1, i1
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( j-i+kb1, i )*conjg( ab( k-i+ka1, &
i ) ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1, i ) +real( ab( ka1, i ),&
KIND=${ck}$)*bb( j-i+kb1, i )*conjg( bb( k-i+kb1, i ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -conjg( bb( k-i+kb1, i ) )*ab( j-i+ka1,&
i )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( k-i+kb1, i )*ab( i-j+ka1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ci}$dscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ci}$gerc( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kb1-kbt, i )&
, 1_${ik}$, x( m+1, i-kbt ),ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+ka1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_130: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i,i-k+ka+1)
call stdlib${ii}$_${ci}$lartg( ab( k+1, i-k+ka ), ra1,rwork( i-k+ka-m ), work( i-k+ka-&
m ), ra )
! create nonzero element a(i-k,i-k+ka+1) outside the
! band and store it in work(i-k)
t = -bb( kb1-k, i )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( 1_${ik}$, i-k+ka &
)
ab( 1_${ik}$, i-k+ka ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( 1_${ik}$, i-k+ka )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j-m )*ab( 1_${ik}$, j+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$largv( nrt, ab( 1_${ik}$, j2t ), inca, work( j2t-m ), ka1,rwork(&
j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2-m ),work( j2-m ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_${ci}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), &
conjg( work( j-m ) ) )
end do
end if
end do loop_130
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt,i-kbt+ka+1) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kb1-kbt, i )*ra1
end if
end if
loop_170: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j2-l+1 ), inca,ab( l+1, j2-l+1 ), &
inca, rwork( j2-ka ),work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j-ka,j+1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+1 )
ab( 1_${ik}$, j+1 ) = rwork( j )*ab( 1_${ik}$, j+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_170
loop_210: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( 1_${ik}$, j2 ), inca, work( j2 ), ka1,rwork( j2 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( ka1-l, j2 ), inca,ab( ka-l, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( ka1, j2 ), ab( ka1, j2+1 ),ab( ka, j2+1 ), inca, &
rwork( j2 ),work( j2 ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_${ci}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), conjg( &
work( j ) ) )
end do
end if
end do loop_210
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j2+ka1-l ), inca,ab( l+1, j2+ka1-l &
), inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=${ck}$)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=${ck}$) / bii ) / bii
do j = i + 1, i1
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do j = max( 1, i-ka ), i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do k = i - kbt, i - 1
do j = i - kbt, k
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( i-j+1, j )*conjg( ab( i-k+1,k ) ) - &
conjg( bb( i-k+1, k ) )*ab( i-j+1, j ) + real( ab( 1_${ik}$, i ),KIND=${ck}$)*bb( i-j+&
1_${ik}$, j )*conjg( bb( i-k+1,k ) )
end do
do j = max( 1, i-ka ), i - kbt - 1
ab( k-j+1, j ) = ab( k-j+1, j ) -conjg( bb( i-k+1, k ) )*ab( i-j+1, j )
end do
end do
do j = i, i1
do k = max( j-ka, i-kbt ), i - 1
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( i-k+1, k )*ab( j-i+1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ci}$dscal( n-m, one / bii, x( m+1, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ci}$geru( n-m, kbt, -cone, x( m+1, i ), 1_${ik}$,bb( kbt+1, i-&
kbt ), ldbb-1,x( m+1, i-kbt ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions down toward the bottom of the
! band
loop_360: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i-k+ka<n .and. i-k>1_${ik}$ ) then
! generate rotation to annihilate a(i-k+ka+1,i)
call stdlib${ii}$_${ci}$lartg( ab( ka1-k, i ), ra1, rwork( i-k+ka-m ),work( i-k+ka-m )&
, ra )
! create nonzero element a(i-k+ka+1,i-k) outside the
! band and store it in work(i-k)
t = -bb( k+1, i-k )*ra1
work( i-k ) = rwork( i-k+ka-m )*t -conjg( work( i-k+ka-m ) )*ab( ka1, i-k )
ab( ka1, i-k ) = work( i-k+ka-m )*t +rwork( i-k+ka-m )*ab( ka1, i-k )
ra1 = ra
end if
end if
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( update ) then
j2t = max( j2, i+2*ka-k+1 )
else
j2t = j2
end if
nrt = ( n-j2t+ka ) / ka1
do j = j2t, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j-m)
work( j-m ) = work( j-m )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j-m )*ab( ka1, j-ka+1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$largv( nrt, ab( ka1, j2t-ka ), inca, work( j2t-m ),ka1, &
rwork( j2t-m ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2-m ),work( j2-m ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2-m ), work( j2-m ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j2-m ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j2, j1, ka1
call stdlib${ii}$_${ci}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j-m ), work(&
j-m ) )
end do
end if
end do loop_360
if( update ) then
if( i2<=n .and. kbt>0_${ik}$ ) then
! create nonzero element a(i-kbt+ka+1,i-kbt) outside the
! band and store it in work(i-kbt)
work( i-kbt ) = -bb( kbt+1, i-kbt )*ra1
end if
end if
loop_400: do k = kb, 1, -1
if( update ) then
j2 = i - k - 1_${ik}$ + max( 2_${ik}$, k-i0+1 )*ka1
else
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+ka+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j2-ka ), inca,ab( ka1-l, j2-&
ka+1 ), inca,rwork( j2-ka ), work( j2-ka ), ka1 )
end do
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
do j = j1, j2, -ka1
work( j ) = work( j-ka )
rwork( j ) = rwork( j-ka )
end do
do j = j2, j1, ka1
! create nonzero element a(j+1,j-ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-ka+1 )
ab( ka1, j-ka+1 ) = rwork( j )*ab( ka1, j-ka+1 )
end do
if( update ) then
if( i-k<n-ka .and. k<=kbt )work( i-k+ka ) = work( i-k )
end if
end do loop_400
loop_440: do k = kb, 1, -1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+1 )*ka1
nr = ( n-j2+ka ) / ka1
j1 = j2 + ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( ka1, j2-ka ), inca, work( j2 ), ka1,rwork( j2 ), &
ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( l+1, j2-l ), inca,ab( l+2, j2-l ), inca, rwork(&
j2 ),work( j2 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( 1_${ik}$, j2 ), ab( 1_${ik}$, j2+1 ), ab( 2_${ik}$, j2 ),inca, rwork( &
j2 ), work( j2 ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j2 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2 ),work( j2 ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j2, j1, ka1
call stdlib${ii}$_${ci}$rot( n-m, x( m+1, j ), 1_${ik}$, x( m+1, j+1 ), 1_${ik}$,rwork( j ), work( &
j ) )
end do
end if
end do loop_440
do k = 1, kb - 1
j2 = i - k - 1_${ik}$ + max( 1_${ik}$, k-i0+2 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( n-j2+l ) / ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j2 ), inca,ab( ka1-l, j2+1 ),&
inca, rwork( j2-m ),work( j2-m ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = n - 1, j2 + ka, -1
rwork( j-m ) = rwork( j-ka-m )
work( j-m ) = work( j-ka-m )
end do
end if
end if
go to 10
480 continue
! **************************** phase 2 *****************************
! the logical structure of this phase is:
! update = .true.
! do i = 1, m
! use s(i) to update a and create a new bulge
! apply rotations to push all bulges ka positions upward
! end do
! update = .false.
! do i = m - ka - 1, 2, -1
! apply rotations to push all bulges ka positions upward
! end do
! to avoid duplicating code, the two loops are merged.
update = .true.
i = 0_${ik}$
490 continue
if( update ) then
i = i + 1_${ik}$
kbt = min( kb, m-i )
i0 = i + 1_${ik}$
i1 = max( 1_${ik}$, i-ka )
i2 = i + kbt - ka1
if( i>m ) then
update = .false.
i = i - 1_${ik}$
i0 = m + 1_${ik}$
if( ka==0 )return
go to 490
end if
else
i = i - ka
if( i<2 )return
end if
if( i<m-kbt ) then
nx = m
else
nx = n
end if
if( upper ) then
! transform a, working with the upper triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( kb1, i ),KIND=${ck}$)
ab( ka1, i ) = ( real( ab( ka1, i ),KIND=${ck}$) / bii ) / bii
do j = i1, i - 1
ab( j-i+ka1, i ) = ab( j-i+ka1, i ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( i-j+ka1, j ) = ab( i-j+ka1, j ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -bb( i-j+kb1, j )*conjg( ab( i-k+ka1, &
k ) ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1, j ) +real( ab( ka1, i ),&
KIND=${ck}$)*bb( i-j+kb1, j )*conjg( bb( i-k+kb1, k ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( k-j+ka1, j ) = ab( k-j+ka1, j ) -conjg( bb( i-k+kb1, k ) )*ab( i-j+ka1,&
j )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( j-k+ka1, k ) = ab( j-k+ka1, k ) -bb( i-k+kb1, k )*ab( j-i+ka1, i )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ci}$dscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ci}$geru( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$,bb( kb, i+1 ), &
ldbb-1, x( 1_${ik}$, i+1 ), ldx )
end if
! store a(i1,i) in ra1 for use in next loop over k
ra1 = ab( i1-i+ka1, i )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_610: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i+k-ka-1,i)
call stdlib${ii}$_${ci}$lartg( ab( k+1, i ), ra1, rwork( i+k-ka ),work( i+k-ka ), ra )
! create nonzero element a(i+k-ka-1,i+k) outside the
! band and store it in work(m-kb+i+k)
t = -bb( kb1-k, i+k )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( 1_${ik}$, i+k )
ab( 1_${ik}$, i+k ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( 1_${ik}$, i+k )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( j )*ab( 1_${ik}$, j+ka-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$largv( nrt, ab( 1_${ik}$, j1+ka ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( j1 ),work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( j1 ), work( j1 ),ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_${ci}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), work( j ) )
end do
end if
end do loop_610
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt-ka-1,i+kbt) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kb1-kbt, i+kbt )*ra1
end if
end if
loop_650: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the right
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j1t+ka ), inca,ab( l+1, j1t+ka-1 ),&
inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j-1,j+ka) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
ab( 1_${ik}$, j+ka-1 ) = rwork( m-kb+j )*ab( 1_${ik}$, j+ka-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_650
loop_690: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( 1_${ik}$, j1+ka ), inca, work( m-kb+j1 ),ka1, rwork( m-&
kb+j1 ), ka1 )
! apply rotations in 2nd set from the left
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( ka1-l, j1+l ), inca,ab( ka-l, j1+l ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( ka1, j1 ), ab( ka1, j1-1 ),ab( ka, j1 ), inca, &
rwork( m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the right
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_${ci}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), work( &
m-kb+j ) )
end do
end if
end do loop_690
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the right
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l, j1t ), inca,ab( l+1, j1t-1 ), inca,&
rwork( j1t ),work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
else
! transform a, working with the lower triangle
if( update ) then
! form inv(s(i))**h * a * inv(s(i))
bii = real( bb( 1_${ik}$, i ),KIND=${ck}$)
ab( 1_${ik}$, i ) = ( real( ab( 1_${ik}$, i ),KIND=${ck}$) / bii ) / bii
do j = i1, i - 1
ab( i-j+1, j ) = ab( i-j+1, j ) / bii
end do
do j = i + 1, min( n, i+ka )
ab( j-i+1, i ) = ab( j-i+1, i ) / bii
end do
do k = i + 1, i + kbt
do j = k, i + kbt
ab( j-k+1, k ) = ab( j-k+1, k ) -bb( j-i+1, i )*conjg( ab( k-i+1,i ) ) - &
conjg( bb( k-i+1, i ) )*ab( j-i+1, i ) + real( ab( 1_${ik}$, i ),KIND=${ck}$)*bb( j-i+&
1_${ik}$, i )*conjg( bb( k-i+1,i ) )
end do
do j = i + kbt + 1, min( n, i+ka )
ab( j-k+1, k ) = ab( j-k+1, k ) -conjg( bb( k-i+1, i ) )*ab( j-i+1, i )
end do
end do
do j = i1, i
do k = i + 1, min( j+ka, i+kbt )
ab( k-j+1, j ) = ab( k-j+1, j ) -bb( k-i+1, i )*ab( i-j+1, j )
end do
end do
if( wantx ) then
! post-multiply x by inv(s(i))
call stdlib${ii}$_${ci}$dscal( nx, one / bii, x( 1_${ik}$, i ), 1_${ik}$ )
if( kbt>0_${ik}$ )call stdlib${ii}$_${ci}$gerc( nx, kbt, -cone, x( 1_${ik}$, i ), 1_${ik}$, bb( 2_${ik}$, i ),1_${ik}$, x( &
1_${ik}$, i+1 ), ldx )
end if
! store a(i,i1) in ra1 for use in next loop over k
ra1 = ab( i-i1+1, i1 )
end if
! generate and apply vectors of rotations to chase all the
! existing bulges ka positions up toward the top of the band
loop_840: do k = 1, kb - 1
if( update ) then
! determine the rotations which would annihilate the bulge
! which has in theory just been created
if( i+k-ka1>0_${ik}$ .and. i+k<m ) then
! generate rotation to annihilate a(i,i+k-ka-1)
call stdlib${ii}$_${ci}$lartg( ab( ka1-k, i+k-ka ), ra1,rwork( i+k-ka ), work( i+k-ka &
), ra )
! create nonzero element a(i+k,i+k-ka-1) outside the
! band and store it in work(m-kb+i+k)
t = -bb( k+1, i )*ra1
work( m-kb+i+k ) = rwork( i+k-ka )*t -conjg( work( i+k-ka ) )*ab( ka1, i+k-&
ka )
ab( ka1, i+k-ka ) = work( i+k-ka )*t +rwork( i+k-ka )*ab( ka1, i+k-ka )
ra1 = ra
end if
end if
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( update ) then
j2t = min( j2, i-2*ka+k-1 )
else
j2t = j2
end if
nrt = ( j2t+ka-1 ) / ka1
do j = j1, j2t, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(j)
work( j ) = work( j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( j )*ab( ka1, j-1 )
end do
! generate rotations in 1st set to annihilate elements which
! have been created outside the band
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$largv( nrt, ab( ka1, j1 ), inca, work( j1 ), ka1,rwork( &
j1 ), ka1 )
if( nr>0_${ik}$ ) then
! apply rotations in 1st set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
j1 ), work( j1 ), ka1 )
end do
! apply rotations in 1st set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
j1 ),work( j1 ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( j1 ), ka1 )
end if
! start applying rotations in 1st set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 1st set
do j = j1, j2, ka1
call stdlib${ii}$_${ci}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( j ), conjg( work(&
j ) ) )
end do
end if
end do loop_840
if( update ) then
if( i2>0_${ik}$ .and. kbt>0_${ik}$ ) then
! create nonzero element a(i+kbt,i+kbt-ka-1) outside the
! band and store it in work(m-kb+i+kbt)
work( m-kb+i+kbt ) = -bb( kbt+1, i )*ra1
end if
end if
loop_880: do k = kb, 1, -1
if( update ) then
j2 = i + k + 1_${ik}$ - max( 2_${ik}$, k+i0-m )*ka1
else
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
end if
! finish applying rotations in 2nd set from the left
do l = kb - k, 1, -1
nrt = ( j2+ka+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j1t+l-1 ), inca,ab( ka1-l, &
j1t+l-1 ), inca,rwork( m-kb+j1t+ka ),work( m-kb+j1t+ka ), ka1 )
end do
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
do j = j1, j2, ka1
work( m-kb+j ) = work( m-kb+j+ka )
rwork( m-kb+j ) = rwork( m-kb+j+ka )
end do
do j = j1, j2, ka1
! create nonzero element a(j+ka,j-1) outside the band
! and store it in work(m-kb+j)
work( m-kb+j ) = work( m-kb+j )*ab( ka1, j-1 )
ab( ka1, j-1 ) = rwork( m-kb+j )*ab( ka1, j-1 )
end do
if( update ) then
if( i+k>ka1 .and. k<=kbt )work( m-kb+i+k-ka ) = work( m-kb+i+k )
end if
end do loop_880
loop_920: do k = kb, 1, -1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m )*ka1
nr = ( j2+ka-1 ) / ka1
j1 = j2 - ( nr-1 )*ka1
if( nr>0_${ik}$ ) then
! generate rotations in 2nd set to annihilate elements
! which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( ka1, j1 ), inca, work( m-kb+j1 ),ka1, rwork( m-kb+&
j1 ), ka1 )
! apply rotations in 2nd set from the right
do l = 1, ka - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( l+1, j1 ), inca, ab( l+2, j1-1 ),inca, rwork( &
m-kb+j1 ), work( m-kb+j1 ),ka1 )
end do
! apply rotations in 2nd set from both sides to diagonal
! blocks
call stdlib${ii}$_${ci}$lar2v( nr, ab( 1_${ik}$, j1 ), ab( 1_${ik}$, j1-1 ),ab( 2_${ik}$, j1-1 ), inca, rwork(&
m-kb+j1 ),work( m-kb+j1 ), ka1 )
call stdlib${ii}$_${ci}$lacgv( nr, work( m-kb+j1 ), ka1 )
end if
! start applying rotations in 2nd set from the left
do l = ka - 1, kb - k + 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( m-kb+j1t ), work( m-kb+j1t ),ka1 )
end do
if( wantx ) then
! post-multiply x by product of rotations in 2nd set
do j = j1, j2, ka1
call stdlib${ii}$_${ci}$rot( nx, x( 1_${ik}$, j ), 1_${ik}$, x( 1_${ik}$, j-1 ), 1_${ik}$,rwork( m-kb+j ), conjg( &
work( m-kb+j ) ) )
end do
end if
end do loop_920
do k = 1, kb - 1
j2 = i + k + 1_${ik}$ - max( 1_${ik}$, k+i0-m+1 )*ka1
! finish applying rotations in 1st set from the left
do l = kb - k, 1, -1
nrt = ( j2+l-1 ) / ka1
j1t = j2 - ( nrt-1 )*ka1
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( ka1-l+1, j1t-ka1+l ), inca,ab( ka1-l, &
j1t-ka1+l ), inca,rwork( j1t ), work( j1t ), ka1 )
end do
end do
if( kb>1_${ik}$ ) then
do j = 2, i2 - ka
rwork( j ) = rwork( j+ka )
work( j ) = work( j+ka )
end do
end if
end if
go to 490
end subroutine stdlib${ii}$_${ci}$hbgst
#:endif
#:endfor
pure module subroutine stdlib${ii}$_spbstf( uplo, n, kd, ab, ldab, info )
!! SPBSTF computes a split Cholesky factorization of a real
!! symmetric positive definite band matrix A.
!! This routine is designed to be used in conjunction with SSBGST.
!! The factorization has the form A = S**T*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
real(sp), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(sp) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_sscal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_ssyr( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_sscal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_ssyr( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_sscal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_ssyr( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_sscal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_ssyr( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_spbstf
pure module subroutine stdlib${ii}$_dpbstf( uplo, n, kd, ab, ldab, info )
!! DPBSTF computes a split Cholesky factorization of a real
!! symmetric positive definite band matrix A.
!! This routine is designed to be used in conjunction with DSBGST.
!! The factorization has the form A = S**T*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
real(dp), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(dp) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_dscal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_dsyr( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_dscal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_dsyr( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_dscal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_dsyr( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_dscal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_dsyr( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_dpbstf
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$pbstf( uplo, n, kd, ab, ldab, info )
!! DPBSTF: computes a split Cholesky factorization of a real
!! symmetric positive definite band matrix A.
!! This routine is designed to be used in conjunction with DSBGST.
!! The factorization has the form A = S**T*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
real(${rk}$), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(${rk}$) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_${ri}$scal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_${ri}$syr( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( kd+1, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_${ri}$scal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_${ri}$syr( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**t*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_${ri}$scal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_${ri}$syr( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**t*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = ab( 1_${ik}$, j )
if( ajj<=zero )go to 50
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_${ri}$scal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_${ri}$syr( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_${ri}$pbstf
#:endif
#:endfor
pure module subroutine stdlib${ii}$_cpbstf( uplo, n, kd, ab, ldab, info )
!! CPBSTF computes a split Cholesky factorization of a complex
!! Hermitian positive definite band matrix A.
!! This routine is designed to be used in conjunction with CHBGST.
!! The factorization has the form A = S**H*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
complex(sp), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(sp) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=sp)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_csscal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_cher( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=sp)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_csscal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_clacgv( km, ab( kd, j+1 ), kld )
call stdlib${ii}$_cher( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
call stdlib${ii}$_clacgv( km, ab( kd, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=sp)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_csscal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_clacgv( km, ab( km+1, j-km ), kld )
call stdlib${ii}$_cher( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
call stdlib${ii}$_clacgv( km, ab( km+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=sp)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_csscal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_cher( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_cpbstf
pure module subroutine stdlib${ii}$_zpbstf( uplo, n, kd, ab, ldab, info )
!! ZPBSTF computes a split Cholesky factorization of a complex
!! Hermitian positive definite band matrix A.
!! This routine is designed to be used in conjunction with ZHBGST.
!! The factorization has the form A = S**H*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
complex(dp), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(dp) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=dp)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_zdscal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_zher( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=dp)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_zdscal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_zlacgv( km, ab( kd, j+1 ), kld )
call stdlib${ii}$_zher( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
call stdlib${ii}$_zlacgv( km, ab( kd, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=dp)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_zdscal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_zlacgv( km, ab( km+1, j-km ), kld )
call stdlib${ii}$_zher( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
call stdlib${ii}$_zlacgv( km, ab( km+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=dp)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_zdscal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_zher( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_zpbstf
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$pbstf( uplo, n, kd, ab, ldab, info )
!! ZPBSTF: computes a split Cholesky factorization of a complex
!! Hermitian positive definite band matrix A.
!! This routine is designed to be used in conjunction with ZHBGST.
!! The factorization has the form A = S**H*S where S is a band matrix
!! of the same bandwidth as A and the following structure:
!! S = ( U )
!! ( M L )
!! where U is upper triangular of order m = (n+kd)/2, and L is lower
!! triangular of order n-m.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, n
! Array Arguments
complex(${ck}$), intent(inout) :: ab(ldab,*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: j, kld, km, m
real(${ck}$) :: ajj
! Intrinsic Functions
! Executable Statements
! test the input parameters.
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( kd<0_${ik}$ ) then
info = -3_${ik}$
else if( ldab<kd+1 ) then
info = -5_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZPBSTF', -info )
return
end if
! quick return if possible
if( n==0 )return
kld = max( 1_${ik}$, ldab-1 )
! set the splitting point m.
m = ( n+kd ) / 2_${ik}$
if( upper ) then
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=${ck}$)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th column and update the
! the leading submatrix within the band.
call stdlib${ii}$_${ci}$dscal( km, one / ajj, ab( kd+1-km, j ), 1_${ik}$ )
call stdlib${ii}$_${ci}$her( 'UPPER', km, -one, ab( kd+1-km, j ), 1_${ik}$,ab( kd+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( kd+1, j ),KIND=${ck}$)
if( ajj<=zero ) then
ab( kd+1, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( kd+1, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th row and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_${ci}$dscal( km, one / ajj, ab( kd, j+1 ), kld )
call stdlib${ii}$_${ci}$lacgv( km, ab( kd, j+1 ), kld )
call stdlib${ii}$_${ci}$her( 'UPPER', km, -one, ab( kd, j+1 ), kld,ab( kd+1, j+1 ), kld )
call stdlib${ii}$_${ci}$lacgv( km, ab( kd, j+1 ), kld )
end if
end do
else
! factorize a(m+1:n,m+1:n) as l**h*l, and update a(1:m,1:m).
do j = n, m + 1, -1
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=${ck}$)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( j-1, kd )
! compute elements j-km:j-1 of the j-th row and update the
! trailing submatrix within the band.
call stdlib${ii}$_${ci}$dscal( km, one / ajj, ab( km+1, j-km ), kld )
call stdlib${ii}$_${ci}$lacgv( km, ab( km+1, j-km ), kld )
call stdlib${ii}$_${ci}$her( 'LOWER', km, -one, ab( km+1, j-km ), kld,ab( 1_${ik}$, j-km ), kld )
call stdlib${ii}$_${ci}$lacgv( km, ab( km+1, j-km ), kld )
end do
! factorize the updated submatrix a(1:m,1:m) as u**h*u.
do j = 1, m
! compute s(j,j) and test for non-positive-definiteness.
ajj = real( ab( 1_${ik}$, j ),KIND=${ck}$)
if( ajj<=zero ) then
ab( 1_${ik}$, j ) = ajj
go to 50
end if
ajj = sqrt( ajj )
ab( 1_${ik}$, j ) = ajj
km = min( kd, m-j )
! compute elements j+1:j+km of the j-th column and update the
! trailing submatrix within the band.
if( km>0_${ik}$ ) then
call stdlib${ii}$_${ci}$dscal( km, one / ajj, ab( 2_${ik}$, j ), 1_${ik}$ )
call stdlib${ii}$_${ci}$her( 'LOWER', km, -one, ab( 2_${ik}$, j ), 1_${ik}$,ab( 1_${ik}$, j+1 ), kld )
end if
end do
end if
return
50 continue
info = j
return
end subroutine stdlib${ii}$_${ci}$pbstf
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slag2( a, lda, b, ldb, safmin, scale1, scale2, wr1,wr2, wi )
!! SLAG2 computes the eigenvalues of a 2 x 2 generalized eigenvalue
!! problem A - w B, with scaling as necessary to avoid over-/underflow.
!! The scaling factor "s" results in a modified eigenvalue equation
!! s A - w B
!! where s is a non-negative scaling factor chosen so that w, w B,
!! and s A do not overflow and, if possible, do not underflow, either.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(in) :: lda, ldb
real(sp), intent(in) :: safmin
real(sp), intent(out) :: scale1, scale2, wi, wr1, wr2
! Array Arguments
real(sp), intent(in) :: a(lda,*), b(ldb,*)
! =====================================================================
! Parameters
real(sp), parameter :: fuzzy1 = one+1.0e-5_sp
! Local Scalars
real(sp) :: a11, a12, a21, a22, abi22, anorm, as11, as12, as22, ascale, b11, b12, b22, &
binv11, binv22, bmin, bnorm, bscale, bsize, c1, c2, c3, c4, c5, diff, discr, pp, qq, r,&
rtmax, rtmin, s1, s2, safmax, shift, ss, sum, wabs, wbig, wdet, wscale, wsize, &
wsmall
! Intrinsic Functions
! Executable Statements
rtmin = sqrt( safmin )
rtmax = one / rtmin
safmax = one / safmin
! scale a
anorm = max( abs( a( 1_${ik}$, 1_${ik}$ ) )+abs( a( 2_${ik}$, 1_${ik}$ ) ),abs( a( 1_${ik}$, 2_${ik}$ ) )+abs( a( 2_${ik}$, 2_${ik}$ ) ), &
safmin )
ascale = one / anorm
a11 = ascale*a( 1_${ik}$, 1_${ik}$ )
a21 = ascale*a( 2_${ik}$, 1_${ik}$ )
a12 = ascale*a( 1_${ik}$, 2_${ik}$ )
a22 = ascale*a( 2_${ik}$, 2_${ik}$ )
! perturb b if necessary to insure non-singularity
b11 = b( 1_${ik}$, 1_${ik}$ )
b12 = b( 1_${ik}$, 2_${ik}$ )
b22 = b( 2_${ik}$, 2_${ik}$ )
bmin = rtmin*max( abs( b11 ), abs( b12 ), abs( b22 ), rtmin )
if( abs( b11 )<bmin )b11 = sign( bmin, b11 )
if( abs( b22 )<bmin )b22 = sign( bmin, b22 )
! scale b
bnorm = max( abs( b11 ), abs( b12 )+abs( b22 ), safmin )
bsize = max( abs( b11 ), abs( b22 ) )
bscale = one / bsize
b11 = b11*bscale
b12 = b12*bscale
b22 = b22*bscale
! compute larger eigenvalue by method described by c. van loan
! ( as is a shifted by -shift*b )
binv11 = one / b11
binv22 = one / b22
s1 = a11*binv11
s2 = a22*binv22
if( abs( s1 )<=abs( s2 ) ) then
as12 = a12 - s1*b12
as22 = a22 - s1*b22
ss = a21*( binv11*binv22 )
abi22 = as22*binv22 - ss*b12
pp = half*abi22
shift = s1
else
as12 = a12 - s2*b12
as11 = a11 - s2*b11
ss = a21*( binv11*binv22 )
abi22 = -ss*b12
pp = half*( as11*binv11+abi22 )
shift = s2
end if
qq = ss*as12
if( abs( pp*rtmin )>=one ) then
discr = ( rtmin*pp )**2_${ik}$ + qq*safmin
r = sqrt( abs( discr ) )*rtmax
else
if( pp**2_${ik}$+abs( qq )<=safmin ) then
discr = ( rtmax*pp )**2_${ik}$ + qq*safmax
r = sqrt( abs( discr ) )*rtmin
else
discr = pp**2_${ik}$ + qq
r = sqrt( abs( discr ) )
end if
end if
! note: the test of r in the following if is to cover the case when
! discr is small and negative and is flushed to zero during
! the calculation of r. on machines which have a consistent
! flush-to-zero threshold and handle numbers above that
! threshold correctly, it would not be necessary.
if( discr>=zero .or. r==zero ) then
sum = pp + sign( r, pp )
diff = pp - sign( r, pp )
wbig = shift + sum
! compute smaller eigenvalue
wsmall = shift + diff
if( half*abs( wbig )>max( abs( wsmall ), safmin ) ) then
wdet = ( a11*a22-a12*a21 )*( binv11*binv22 )
wsmall = wdet / wbig
end if
! choose (real) eigenvalue closest to 2,2 element of a*b**(-1)
! for wr1.
if( pp>abi22 ) then
wr1 = min( wbig, wsmall )
wr2 = max( wbig, wsmall )
else
wr1 = max( wbig, wsmall )
wr2 = min( wbig, wsmall )
end if
wi = zero
else
! complex eigenvalues
wr1 = shift + pp
wr2 = wr1
wi = r
end if
! further scaling to avoid underflow and overflow in computing
! scale1 and overflow in computing w*b.
! this scale factor (wscale) is bounded from above using c1 and c2,
! and from below using c3 and c4.
! c1 implements the condition s a must never overflow.
! c2 implements the condition w b must never overflow.
! c3, with c2,
! implement the condition that s a - w b must never overflow.
! c4 implements the condition s should not underflow.
! c5 implements the condition max(s,|w|) should be at least 2.
c1 = bsize*( safmin*max( one, ascale ) )
c2 = safmin*max( one, bnorm )
c3 = bsize*safmin
if( ascale<=one .and. bsize<=one ) then
c4 = min( one, ( ascale / safmin )*bsize )
else
c4 = one
end if
if( ascale<=one .or. bsize<=one ) then
c5 = min( one, ascale*bsize )
else
c5 = one
end if
! scale first eigenvalue
wabs = abs( wr1 ) + abs( wi )
wsize = max( safmin, c1, fuzzy1*( wabs*c2+c3 ),min( c4, half*max( wabs, c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale1 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale1 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr1 = wr1*wscale
if( wi/=zero ) then
wi = wi*wscale
wr2 = wr1
scale2 = scale1
end if
else
scale1 = ascale*bsize
scale2 = scale1
end if
! scale second eigenvalue (if real)
if( wi==zero ) then
wsize = max( safmin, c1, fuzzy1*( abs( wr2 )*c2+c3 ),min( c4, half*max( abs( wr2 ), &
c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale2 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale2 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr2 = wr2*wscale
else
scale2 = ascale*bsize
end if
end if
return
end subroutine stdlib${ii}$_slag2
pure module subroutine stdlib${ii}$_dlag2( a, lda, b, ldb, safmin, scale1, scale2, wr1,wr2, wi )
!! DLAG2 computes the eigenvalues of a 2 x 2 generalized eigenvalue
!! problem A - w B, with scaling as necessary to avoid over-/underflow.
!! The scaling factor "s" results in a modified eigenvalue equation
!! s A - w B
!! where s is a non-negative scaling factor chosen so that w, w B,
!! and s A do not overflow and, if possible, do not underflow, either.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(in) :: lda, ldb
real(dp), intent(in) :: safmin
real(dp), intent(out) :: scale1, scale2, wi, wr1, wr2
! Array Arguments
real(dp), intent(in) :: a(lda,*), b(ldb,*)
! =====================================================================
! Parameters
real(dp), parameter :: fuzzy1 = one+1.0e-5_dp
! Local Scalars
real(dp) :: a11, a12, a21, a22, abi22, anorm, as11, as12, as22, ascale, b11, b12, b22, &
binv11, binv22, bmin, bnorm, bscale, bsize, c1, c2, c3, c4, c5, diff, discr, pp, qq, r,&
rtmax, rtmin, s1, s2, safmax, shift, ss, sum, wabs, wbig, wdet, wscale, wsize, &
wsmall
! Intrinsic Functions
! Executable Statements
rtmin = sqrt( safmin )
rtmax = one / rtmin
safmax = one / safmin
! scale a
anorm = max( abs( a( 1_${ik}$, 1_${ik}$ ) )+abs( a( 2_${ik}$, 1_${ik}$ ) ),abs( a( 1_${ik}$, 2_${ik}$ ) )+abs( a( 2_${ik}$, 2_${ik}$ ) ), &
safmin )
ascale = one / anorm
a11 = ascale*a( 1_${ik}$, 1_${ik}$ )
a21 = ascale*a( 2_${ik}$, 1_${ik}$ )
a12 = ascale*a( 1_${ik}$, 2_${ik}$ )
a22 = ascale*a( 2_${ik}$, 2_${ik}$ )
! perturb b if necessary to insure non-singularity
b11 = b( 1_${ik}$, 1_${ik}$ )
b12 = b( 1_${ik}$, 2_${ik}$ )
b22 = b( 2_${ik}$, 2_${ik}$ )
bmin = rtmin*max( abs( b11 ), abs( b12 ), abs( b22 ), rtmin )
if( abs( b11 )<bmin )b11 = sign( bmin, b11 )
if( abs( b22 )<bmin )b22 = sign( bmin, b22 )
! scale b
bnorm = max( abs( b11 ), abs( b12 )+abs( b22 ), safmin )
bsize = max( abs( b11 ), abs( b22 ) )
bscale = one / bsize
b11 = b11*bscale
b12 = b12*bscale
b22 = b22*bscale
! compute larger eigenvalue by method described by c. van loan
! ( as is a shifted by -shift*b )
binv11 = one / b11
binv22 = one / b22
s1 = a11*binv11
s2 = a22*binv22
if( abs( s1 )<=abs( s2 ) ) then
as12 = a12 - s1*b12
as22 = a22 - s1*b22
ss = a21*( binv11*binv22 )
abi22 = as22*binv22 - ss*b12
pp = half*abi22
shift = s1
else
as12 = a12 - s2*b12
as11 = a11 - s2*b11
ss = a21*( binv11*binv22 )
abi22 = -ss*b12
pp = half*( as11*binv11+abi22 )
shift = s2
end if
qq = ss*as12
if( abs( pp*rtmin )>=one ) then
discr = ( rtmin*pp )**2_${ik}$ + qq*safmin
r = sqrt( abs( discr ) )*rtmax
else
if( pp**2_${ik}$+abs( qq )<=safmin ) then
discr = ( rtmax*pp )**2_${ik}$ + qq*safmax
r = sqrt( abs( discr ) )*rtmin
else
discr = pp**2_${ik}$ + qq
r = sqrt( abs( discr ) )
end if
end if
! note: the test of r in the following if is to cover the case when
! discr is small and negative and is flushed to zero during
! the calculation of r. on machines which have a consistent
! flush-to-zero threshold and handle numbers above that
! threshold correctly, it would not be necessary.
if( discr>=zero .or. r==zero ) then
sum = pp + sign( r, pp )
diff = pp - sign( r, pp )
wbig = shift + sum
! compute smaller eigenvalue
wsmall = shift + diff
if( half*abs( wbig )>max( abs( wsmall ), safmin ) ) then
wdet = ( a11*a22-a12*a21 )*( binv11*binv22 )
wsmall = wdet / wbig
end if
! choose (real) eigenvalue closest to 2,2 element of a*b**(-1)
! for wr1.
if( pp>abi22 ) then
wr1 = min( wbig, wsmall )
wr2 = max( wbig, wsmall )
else
wr1 = max( wbig, wsmall )
wr2 = min( wbig, wsmall )
end if
wi = zero
else
! complex eigenvalues
wr1 = shift + pp
wr2 = wr1
wi = r
end if
! further scaling to avoid underflow and overflow in computing
! scale1 and overflow in computing w*b.
! this scale factor (wscale) is bounded from above using c1 and c2,
! and from below using c3 and c4.
! c1 implements the condition s a must never overflow.
! c2 implements the condition w b must never overflow.
! c3, with c2,
! implement the condition that s a - w b must never overflow.
! c4 implements the condition s should not underflow.
! c5 implements the condition max(s,|w|) should be at least 2.
c1 = bsize*( safmin*max( one, ascale ) )
c2 = safmin*max( one, bnorm )
c3 = bsize*safmin
if( ascale<=one .and. bsize<=one ) then
c4 = min( one, ( ascale / safmin )*bsize )
else
c4 = one
end if
if( ascale<=one .or. bsize<=one ) then
c5 = min( one, ascale*bsize )
else
c5 = one
end if
! scale first eigenvalue
wabs = abs( wr1 ) + abs( wi )
wsize = max( safmin, c1, fuzzy1*( wabs*c2+c3 ),min( c4, half*max( wabs, c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale1 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale1 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr1 = wr1*wscale
if( wi/=zero ) then
wi = wi*wscale
wr2 = wr1
scale2 = scale1
end if
else
scale1 = ascale*bsize
scale2 = scale1
end if
! scale second eigenvalue (if real)
if( wi==zero ) then
wsize = max( safmin, c1, fuzzy1*( abs( wr2 )*c2+c3 ),min( c4, half*max( abs( wr2 ), &
c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale2 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale2 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr2 = wr2*wscale
else
scale2 = ascale*bsize
end if
end if
return
end subroutine stdlib${ii}$_dlag2
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$lag2( a, lda, b, ldb, safmin, scale1, scale2, wr1,wr2, wi )
!! DLAG2: computes the eigenvalues of a 2 x 2 generalized eigenvalue
!! problem A - w B, with scaling as necessary to avoid over-/underflow.
!! The scaling factor "s" results in a modified eigenvalue equation
!! s A - w B
!! where s is a non-negative scaling factor chosen so that w, w B,
!! and s A do not overflow and, if possible, do not underflow, either.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(in) :: lda, ldb
real(${rk}$), intent(in) :: safmin
real(${rk}$), intent(out) :: scale1, scale2, wi, wr1, wr2
! Array Arguments
real(${rk}$), intent(in) :: a(lda,*), b(ldb,*)
! =====================================================================
! Parameters
real(${rk}$), parameter :: fuzzy1 = one+1.0e-5_${rk}$
! Local Scalars
real(${rk}$) :: a11, a12, a21, a22, abi22, anorm, as11, as12, as22, ascale, b11, b12, b22, &
binv11, binv22, bmin, bnorm, bscale, bsize, c1, c2, c3, c4, c5, diff, discr, pp, qq, r,&
rtmax, rtmin, s1, s2, safmax, shift, ss, sum, wabs, wbig, wdet, wscale, wsize, &
wsmall
! Intrinsic Functions
! Executable Statements
rtmin = sqrt( safmin )
rtmax = one / rtmin
safmax = one / safmin
! scale a
anorm = max( abs( a( 1_${ik}$, 1_${ik}$ ) )+abs( a( 2_${ik}$, 1_${ik}$ ) ),abs( a( 1_${ik}$, 2_${ik}$ ) )+abs( a( 2_${ik}$, 2_${ik}$ ) ), &
safmin )
ascale = one / anorm
a11 = ascale*a( 1_${ik}$, 1_${ik}$ )
a21 = ascale*a( 2_${ik}$, 1_${ik}$ )
a12 = ascale*a( 1_${ik}$, 2_${ik}$ )
a22 = ascale*a( 2_${ik}$, 2_${ik}$ )
! perturb b if necessary to insure non-singularity
b11 = b( 1_${ik}$, 1_${ik}$ )
b12 = b( 1_${ik}$, 2_${ik}$ )
b22 = b( 2_${ik}$, 2_${ik}$ )
bmin = rtmin*max( abs( b11 ), abs( b12 ), abs( b22 ), rtmin )
if( abs( b11 )<bmin )b11 = sign( bmin, b11 )
if( abs( b22 )<bmin )b22 = sign( bmin, b22 )
! scale b
bnorm = max( abs( b11 ), abs( b12 )+abs( b22 ), safmin )
bsize = max( abs( b11 ), abs( b22 ) )
bscale = one / bsize
b11 = b11*bscale
b12 = b12*bscale
b22 = b22*bscale
! compute larger eigenvalue by method described by c. van loan
! ( as is a shifted by -shift*b )
binv11 = one / b11
binv22 = one / b22
s1 = a11*binv11
s2 = a22*binv22
if( abs( s1 )<=abs( s2 ) ) then
as12 = a12 - s1*b12
as22 = a22 - s1*b22
ss = a21*( binv11*binv22 )
abi22 = as22*binv22 - ss*b12
pp = half*abi22
shift = s1
else
as12 = a12 - s2*b12
as11 = a11 - s2*b11
ss = a21*( binv11*binv22 )
abi22 = -ss*b12
pp = half*( as11*binv11+abi22 )
shift = s2
end if
qq = ss*as12
if( abs( pp*rtmin )>=one ) then
discr = ( rtmin*pp )**2_${ik}$ + qq*safmin
r = sqrt( abs( discr ) )*rtmax
else
if( pp**2_${ik}$+abs( qq )<=safmin ) then
discr = ( rtmax*pp )**2_${ik}$ + qq*safmax
r = sqrt( abs( discr ) )*rtmin
else
discr = pp**2_${ik}$ + qq
r = sqrt( abs( discr ) )
end if
end if
! note: the test of r in the following if is to cover the case when
! discr is small and negative and is flushed to zero during
! the calculation of r. on machines which have a consistent
! flush-to-zero threshold and handle numbers above that
! threshold correctly, it would not be necessary.
if( discr>=zero .or. r==zero ) then
sum = pp + sign( r, pp )
diff = pp - sign( r, pp )
wbig = shift + sum
! compute smaller eigenvalue
wsmall = shift + diff
if( half*abs( wbig )>max( abs( wsmall ), safmin ) ) then
wdet = ( a11*a22-a12*a21 )*( binv11*binv22 )
wsmall = wdet / wbig
end if
! choose (real) eigenvalue closest to 2,2 element of a*b**(-1)
! for wr1.
if( pp>abi22 ) then
wr1 = min( wbig, wsmall )
wr2 = max( wbig, wsmall )
else
wr1 = max( wbig, wsmall )
wr2 = min( wbig, wsmall )
end if
wi = zero
else
! complex eigenvalues
wr1 = shift + pp
wr2 = wr1
wi = r
end if
! further scaling to avoid underflow and overflow in computing
! scale1 and overflow in computing w*b.
! this scale factor (wscale) is bounded from above using c1 and c2,
! and from below using c3 and c4.
! c1 implements the condition s a must never overflow.
! c2 implements the condition w b must never overflow.
! c3, with c2,
! implement the condition that s a - w b must never overflow.
! c4 implements the condition s should not underflow.
! c5 implements the condition max(s,|w|) should be at least 2.
c1 = bsize*( safmin*max( one, ascale ) )
c2 = safmin*max( one, bnorm )
c3 = bsize*safmin
if( ascale<=one .and. bsize<=one ) then
c4 = min( one, ( ascale / safmin )*bsize )
else
c4 = one
end if
if( ascale<=one .or. bsize<=one ) then
c5 = min( one, ascale*bsize )
else
c5 = one
end if
! scale first eigenvalue
wabs = abs( wr1 ) + abs( wi )
wsize = max( safmin, c1, fuzzy1*( wabs*c2+c3 ),min( c4, half*max( wabs, c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale1 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale1 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr1 = wr1*wscale
if( wi/=zero ) then
wi = wi*wscale
wr2 = wr1
scale2 = scale1
end if
else
scale1 = ascale*bsize
scale2 = scale1
end if
! scale second eigenvalue (if real)
if( wi==zero ) then
wsize = max( safmin, c1, fuzzy1*( abs( wr2 )*c2+c3 ),min( c4, half*max( abs( wr2 ), &
c5 ) ) )
if( wsize/=one ) then
wscale = one / wsize
if( wsize>one ) then
scale2 = ( max( ascale, bsize )*wscale )*min( ascale, bsize )
else
scale2 = ( min( ascale, bsize )*wscale )*max( ascale, bsize )
end if
wr2 = wr2*wscale
else
scale2 = ascale*bsize
end if
end if
return
end subroutine stdlib${ii}$_${ri}$lag2
#:endif
#:endfor
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_dlag2${ri}$( m, n, sa, ldsa, a, lda, info )
!! DLAG2Q converts a DOUBLE PRECISION matrix, SA, to an EXTENDED
!! PRECISION matrix, A.
!! Note that while it is possible to overflow while converting
!! from double to single, it is not possible to overflow when
!! converting from single to double.
!! This is an auxiliary routine so there is no argument checking.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: lda, ldsa, m, n
! Array Arguments
real(dp), intent(in) :: sa(ldsa,*)
real(${rk}$), intent(out) :: a(lda,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, j
! Executable Statements
info = 0_${ik}$
do j = 1, n
do i = 1, m
a( i, j ) = sa( i, j )
end do
end do
return
end subroutine stdlib${ii}$_dlag2${ri}$
#:endif
#:endfor
pure module subroutine stdlib${ii}$_sorm22( side, trans, m, n, n1, n2, q, ldq, c, ldc,work, lwork, info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans
integer(${ik}$), intent(in) :: m, n, n1, n2, ldq, ldc, lwork
integer(${ik}$), intent(out) :: info
! Array Arguments
real(sp), intent(in) :: q(ldq,*)
real(sp), intent(inout) :: c(ldc,*)
real(sp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: left, lquery, notran
integer(${ik}$) :: i, ldwork, len, lwkopt, nb, nq, nw
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
lquery = ( lwork==-1_${ik}$ )
! nq is the order of q;
! nw is the minimum dimension of work.
if( left ) then
nq = m
else
nq = n
end if
nw = nq
if( n1==0_${ik}$ .or. n2==0_${ik}$ ) nw = 1_${ik}$
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.stdlib_lsame( trans, 'N' ) .and. .not.stdlib_lsame( trans, 'T' ) )&
then
info = -2_${ik}$
else if( m<0_${ik}$ ) then
info = -3_${ik}$
else if( n<0_${ik}$ ) then
info = -4_${ik}$
else if( n1<0_${ik}$ .or. n1+n2/=nq ) then
info = -5_${ik}$
else if( n2<0_${ik}$ ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, nq ) ) then
info = -8_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -10_${ik}$
else if( lwork<nw .and. .not.lquery ) then
info = -12_${ik}$
end if
if( info==0_${ik}$ ) then
lwkopt = m*n
work( 1_${ik}$ ) = real( lwkopt,KIND=sp)
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SORM22', -info )
return
else if( lquery ) then
return
end if
! quick return if possible
if( m==0_${ik}$ .or. n==0_${ik}$ ) then
work( 1_${ik}$ ) = 1_${ik}$
return
end if
! degenerate cases (n1 = 0 or n2 = 0) are handled using stdlib${ii}$_strmm.
if( n1==0_${ik}$ ) then
call stdlib${ii}$_strmm( side, 'UPPER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
else if( n2==0_${ik}$ ) then
call stdlib${ii}$_strmm( side, 'LOWER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
end if
! compute the largest chunk size available from the workspace.
nb = max( 1_${ik}$, min( lwork, lwkopt ) / nq )
if( left ) then
if( notran ) then
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q12.
call stdlib${ii}$_slacpy( 'ALL', n1, len, c( n2+1, i ), ldc, work,ldwork )
call stdlib${ii}$_strmm( 'LEFT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',n1, len, one, &
q( 1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply top part of c by q11.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q, ldq, c(&
1_${ik}$, i ), ldc, one, work,ldwork )
! multiply top part of c by q21.
call stdlib${ii}$_slacpy( 'ALL', n2, len, c( 1_${ik}$, i ), ldc,work( n1+1 ), ldwork )
call stdlib${ii}$_strmm( 'LEFT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',n2, len, one, &
q( n1+1, 1_${ik}$ ), ldq,work( n1+1 ), ldwork )
! multiply bottom part of c by q22.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q( n1+1, &
n2+1 ), ldq, c( n2+1, i ), ldc,one, work( n1+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_slacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
else
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q21**t.
call stdlib${ii}$_slacpy( 'ALL', n2, len, c( n1+1, i ), ldc, work,ldwork )
call stdlib${ii}$_strmm( 'LEFT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',n2, len, one, q( &
n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply top part of c by q11**t.
call stdlib${ii}$_sgemm( 'TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q, ldq, c( 1_${ik}$,&
i ), ldc, one, work,ldwork )
! multiply top part of c by q12**t.
call stdlib${ii}$_slacpy( 'ALL', n1, len, c( 1_${ik}$, i ), ldc,work( n2+1 ), ldwork )
call stdlib${ii}$_strmm( 'LEFT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',n1, len, one, q( &
1_${ik}$, n2+1 ), ldq,work( n2+1 ), ldwork )
! multiply bottom part of c by q22**t.
call stdlib${ii}$_sgemm( 'TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q( n1+1, n2+&
1_${ik}$ ), ldq, c( n1+1, i ), ldc,one, work( n2+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_slacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
end if
else
if( notran ) then
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q21.
call stdlib${ii}$_slacpy( 'ALL', len, n2, c( i, n1+1 ), ldc, work,ldwork )
call stdlib${ii}$_strmm( 'RIGHT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',len, n2, one, &
q( n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply left part of c by q11.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n2, n1,one, c( i, 1_${ik}$ ),&
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q12.
call stdlib${ii}$_slacpy( 'ALL', len, n1, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n2*ldwork ), &
ldwork )
call stdlib${ii}$_strmm( 'RIGHT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',len, n1, one, &
q( 1_${ik}$, n2+1 ), ldq,work( 1_${ik}$ + n2*ldwork ), ldwork )
! multiply right part of c by q22.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n1, n2,one, c( i, n1+&
1_${ik}$ ), ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n2*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_slacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
else
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q12**t.
call stdlib${ii}$_slacpy( 'ALL', len, n1, c( i, n2+1 ), ldc, work,ldwork )
call stdlib${ii}$_strmm( 'RIGHT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',len, n1, one, q( &
1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply left part of c by q11**t.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n1, n2,one, c( i, 1_${ik}$ ), &
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q21**t.
call stdlib${ii}$_slacpy( 'ALL', len, n2, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n1*ldwork ), &
ldwork )
call stdlib${ii}$_strmm( 'RIGHT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',len, n2, one, q( &
n1+1, 1_${ik}$ ), ldq,work( 1_${ik}$ + n1*ldwork ), ldwork )
! multiply right part of c by q22**t.
call stdlib${ii}$_sgemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n2, n1,one, c( i, n2+1 ),&
ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n1*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_slacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
end if
end if
work( 1_${ik}$ ) = real( lwkopt,KIND=sp)
return
end subroutine stdlib${ii}$_sorm22
pure module subroutine stdlib${ii}$_dorm22( side, trans, m, n, n1, n2, q, ldq, c, ldc,work, lwork, info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans
integer(${ik}$), intent(in) :: m, n, n1, n2, ldq, ldc, lwork
integer(${ik}$), intent(out) :: info
! Array Arguments
real(dp), intent(in) :: q(ldq,*)
real(dp), intent(inout) :: c(ldc,*)
real(dp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: left, lquery, notran
integer(${ik}$) :: i, ldwork, len, lwkopt, nb, nq, nw
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
lquery = ( lwork==-1_${ik}$ )
! nq is the order of q;
! nw is the minimum dimension of work.
if( left ) then
nq = m
else
nq = n
end if
nw = nq
if( n1==0_${ik}$ .or. n2==0_${ik}$ ) nw = 1_${ik}$
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.stdlib_lsame( trans, 'N' ) .and. .not.stdlib_lsame( trans, 'T' ) )&
then
info = -2_${ik}$
else if( m<0_${ik}$ ) then
info = -3_${ik}$
else if( n<0_${ik}$ ) then
info = -4_${ik}$
else if( n1<0_${ik}$ .or. n1+n2/=nq ) then
info = -5_${ik}$
else if( n2<0_${ik}$ ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, nq ) ) then
info = -8_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -10_${ik}$
else if( lwork<nw .and. .not.lquery ) then
info = -12_${ik}$
end if
if( info==0_${ik}$ ) then
lwkopt = m*n
work( 1_${ik}$ ) = real( lwkopt,KIND=dp)
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DORM22', -info )
return
else if( lquery ) then
return
end if
! quick return if possible
if( m==0_${ik}$ .or. n==0_${ik}$ ) then
work( 1_${ik}$ ) = 1_${ik}$
return
end if
! degenerate cases (n1 = 0 or n2 = 0) are handled using stdlib${ii}$_dtrmm.
if( n1==0_${ik}$ ) then
call stdlib${ii}$_dtrmm( side, 'UPPER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
else if( n2==0_${ik}$ ) then
call stdlib${ii}$_dtrmm( side, 'LOWER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
end if
! compute the largest chunk size available from the workspace.
nb = max( 1_${ik}$, min( lwork, lwkopt ) / nq )
if( left ) then
if( notran ) then
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q12.
call stdlib${ii}$_dlacpy( 'ALL', n1, len, c( n2+1, i ), ldc, work,ldwork )
call stdlib${ii}$_dtrmm( 'LEFT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',n1, len, one, &
q( 1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply top part of c by q11.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q, ldq, c(&
1_${ik}$, i ), ldc, one, work,ldwork )
! multiply top part of c by q21.
call stdlib${ii}$_dlacpy( 'ALL', n2, len, c( 1_${ik}$, i ), ldc,work( n1+1 ), ldwork )
call stdlib${ii}$_dtrmm( 'LEFT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',n2, len, one, &
q( n1+1, 1_${ik}$ ), ldq,work( n1+1 ), ldwork )
! multiply bottom part of c by q22.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q( n1+1, &
n2+1 ), ldq, c( n2+1, i ), ldc,one, work( n1+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_dlacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
else
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q21**t.
call stdlib${ii}$_dlacpy( 'ALL', n2, len, c( n1+1, i ), ldc, work,ldwork )
call stdlib${ii}$_dtrmm( 'LEFT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',n2, len, one, q( &
n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply top part of c by q11**t.
call stdlib${ii}$_dgemm( 'TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q, ldq, c( 1_${ik}$,&
i ), ldc, one, work,ldwork )
! multiply top part of c by q12**t.
call stdlib${ii}$_dlacpy( 'ALL', n1, len, c( 1_${ik}$, i ), ldc,work( n2+1 ), ldwork )
call stdlib${ii}$_dtrmm( 'LEFT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',n1, len, one, q( &
1_${ik}$, n2+1 ), ldq,work( n2+1 ), ldwork )
! multiply bottom part of c by q22**t.
call stdlib${ii}$_dgemm( 'TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q( n1+1, n2+&
1_${ik}$ ), ldq, c( n1+1, i ), ldc,one, work( n2+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_dlacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
end if
else
if( notran ) then
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q21.
call stdlib${ii}$_dlacpy( 'ALL', len, n2, c( i, n1+1 ), ldc, work,ldwork )
call stdlib${ii}$_dtrmm( 'RIGHT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',len, n2, one, &
q( n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply left part of c by q11.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n2, n1,one, c( i, 1_${ik}$ ),&
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q12.
call stdlib${ii}$_dlacpy( 'ALL', len, n1, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n2*ldwork ), &
ldwork )
call stdlib${ii}$_dtrmm( 'RIGHT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',len, n1, one, &
q( 1_${ik}$, n2+1 ), ldq,work( 1_${ik}$ + n2*ldwork ), ldwork )
! multiply right part of c by q22.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n1, n2,one, c( i, n1+&
1_${ik}$ ), ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n2*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_dlacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
else
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q12**t.
call stdlib${ii}$_dlacpy( 'ALL', len, n1, c( i, n2+1 ), ldc, work,ldwork )
call stdlib${ii}$_dtrmm( 'RIGHT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',len, n1, one, q( &
1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply left part of c by q11**t.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n1, n2,one, c( i, 1_${ik}$ ), &
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q21**t.
call stdlib${ii}$_dlacpy( 'ALL', len, n2, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n1*ldwork ), &
ldwork )
call stdlib${ii}$_dtrmm( 'RIGHT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',len, n2, one, q( &
n1+1, 1_${ik}$ ), ldq,work( 1_${ik}$ + n1*ldwork ), ldwork )
! multiply right part of c by q22**t.
call stdlib${ii}$_dgemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n2, n1,one, c( i, n2+1 ),&
ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n1*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_dlacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
end if
end if
work( 1_${ik}$ ) = real( lwkopt,KIND=dp)
return
end subroutine stdlib${ii}$_dorm22
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$orm22( side, trans, m, n, n1, n2, q, ldq, c, ldc,work, lwork, info )
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans
integer(${ik}$), intent(in) :: m, n, n1, n2, ldq, ldc, lwork
integer(${ik}$), intent(out) :: info
! Array Arguments
real(${rk}$), intent(in) :: q(ldq,*)
real(${rk}$), intent(inout) :: c(ldc,*)
real(${rk}$), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: left, lquery, notran
integer(${ik}$) :: i, ldwork, len, lwkopt, nb, nq, nw
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
lquery = ( lwork==-1_${ik}$ )
! nq is the order of q;
! nw is the minimum dimension of work.
if( left ) then
nq = m
else
nq = n
end if
nw = nq
if( n1==0_${ik}$ .or. n2==0_${ik}$ ) nw = 1_${ik}$
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.stdlib_lsame( trans, 'N' ) .and. .not.stdlib_lsame( trans, 'T' ) )&
then
info = -2_${ik}$
else if( m<0_${ik}$ ) then
info = -3_${ik}$
else if( n<0_${ik}$ ) then
info = -4_${ik}$
else if( n1<0_${ik}$ .or. n1+n2/=nq ) then
info = -5_${ik}$
else if( n2<0_${ik}$ ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, nq ) ) then
info = -8_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -10_${ik}$
else if( lwork<nw .and. .not.lquery ) then
info = -12_${ik}$
end if
if( info==0_${ik}$ ) then
lwkopt = m*n
work( 1_${ik}$ ) = real( lwkopt,KIND=${rk}$)
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DORM22', -info )
return
else if( lquery ) then
return
end if
! quick return if possible
if( m==0_${ik}$ .or. n==0_${ik}$ ) then
work( 1_${ik}$ ) = 1_${ik}$
return
end if
! degenerate cases (n1 = 0 or n2 = 0) are handled using stdlib${ii}$_${ri}$trmm.
if( n1==0_${ik}$ ) then
call stdlib${ii}$_${ri}$trmm( side, 'UPPER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
else if( n2==0_${ik}$ ) then
call stdlib${ii}$_${ri}$trmm( side, 'LOWER', trans, 'NON-UNIT', m, n, one,q, ldq, c, ldc )
work( 1_${ik}$ ) = one
return
end if
! compute the largest chunk size available from the workspace.
nb = max( 1_${ik}$, min( lwork, lwkopt ) / nq )
if( left ) then
if( notran ) then
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q12.
call stdlib${ii}$_${ri}$lacpy( 'ALL', n1, len, c( n2+1, i ), ldc, work,ldwork )
call stdlib${ii}$_${ri}$trmm( 'LEFT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',n1, len, one, &
q( 1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply top part of c by q11.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q, ldq, c(&
1_${ik}$, i ), ldc, one, work,ldwork )
! multiply top part of c by q21.
call stdlib${ii}$_${ri}$lacpy( 'ALL', n2, len, c( 1_${ik}$, i ), ldc,work( n1+1 ), ldwork )
call stdlib${ii}$_${ri}$trmm( 'LEFT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',n2, len, one, &
q( n1+1, 1_${ik}$ ), ldq,work( n1+1 ), ldwork )
! multiply bottom part of c by q22.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q( n1+1, &
n2+1 ), ldq, c( n2+1, i ), ldc,one, work( n1+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_${ri}$lacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
else
do i = 1, n, nb
len = min( nb, n-i+1 )
ldwork = m
! multiply bottom part of c by q21**t.
call stdlib${ii}$_${ri}$lacpy( 'ALL', n2, len, c( n1+1, i ), ldc, work,ldwork )
call stdlib${ii}$_${ri}$trmm( 'LEFT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',n2, len, one, q( &
n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply top part of c by q11**t.
call stdlib${ii}$_${ri}$gemm( 'TRANSPOSE', 'NO TRANSPOSE', n2, len, n1,one, q, ldq, c( 1_${ik}$,&
i ), ldc, one, work,ldwork )
! multiply top part of c by q12**t.
call stdlib${ii}$_${ri}$lacpy( 'ALL', n1, len, c( 1_${ik}$, i ), ldc,work( n2+1 ), ldwork )
call stdlib${ii}$_${ri}$trmm( 'LEFT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',n1, len, one, q( &
1_${ik}$, n2+1 ), ldq,work( n2+1 ), ldwork )
! multiply bottom part of c by q22**t.
call stdlib${ii}$_${ri}$gemm( 'TRANSPOSE', 'NO TRANSPOSE', n1, len, n2,one, q( n1+1, n2+&
1_${ik}$ ), ldq, c( n1+1, i ), ldc,one, work( n2+1 ), ldwork )
! copy everything back.
call stdlib${ii}$_${ri}$lacpy( 'ALL', m, len, work, ldwork, c( 1_${ik}$, i ),ldc )
end do
end if
else
if( notran ) then
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q21.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n2, c( i, n1+1 ), ldc, work,ldwork )
call stdlib${ii}$_${ri}$trmm( 'RIGHT', 'UPPER', 'NO TRANSPOSE', 'NON-UNIT',len, n2, one, &
q( n1+1, 1_${ik}$ ), ldq, work,ldwork )
! multiply left part of c by q11.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n2, n1,one, c( i, 1_${ik}$ ),&
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q12.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n1, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n2*ldwork ), &
ldwork )
call stdlib${ii}$_${ri}$trmm( 'RIGHT', 'LOWER', 'NO TRANSPOSE', 'NON-UNIT',len, n1, one, &
q( 1_${ik}$, n2+1 ), ldq,work( 1_${ik}$ + n2*ldwork ), ldwork )
! multiply right part of c by q22.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'NO TRANSPOSE', len, n1, n2,one, c( i, n1+&
1_${ik}$ ), ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n2*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
else
do i = 1, m, nb
len = min( nb, m-i+1 )
ldwork = len
! multiply right part of c by q12**t.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n1, c( i, n2+1 ), ldc, work,ldwork )
call stdlib${ii}$_${ri}$trmm( 'RIGHT', 'LOWER', 'TRANSPOSE', 'NON-UNIT',len, n1, one, q( &
1_${ik}$, n2+1 ), ldq, work,ldwork )
! multiply left part of c by q11**t.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n1, n2,one, c( i, 1_${ik}$ ), &
ldc, q, ldq, one, work,ldwork )
! multiply left part of c by q21**t.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n2, c( i, 1_${ik}$ ), ldc,work( 1_${ik}$ + n1*ldwork ), &
ldwork )
call stdlib${ii}$_${ri}$trmm( 'RIGHT', 'UPPER', 'TRANSPOSE', 'NON-UNIT',len, n2, one, q( &
n1+1, 1_${ik}$ ), ldq,work( 1_${ik}$ + n1*ldwork ), ldwork )
! multiply right part of c by q22**t.
call stdlib${ii}$_${ri}$gemm( 'NO TRANSPOSE', 'TRANSPOSE', len, n2, n1,one, c( i, n2+1 ),&
ldc, q( n1+1, n2+1 ), ldq,one, work( 1_${ik}$ + n1*ldwork ), ldwork )
! copy everything back.
call stdlib${ii}$_${ri}$lacpy( 'ALL', len, n, work, ldwork, c( i, 1_${ik}$ ),ldc )
end do
end if
end if
work( 1_${ik}$ ) = real( lwkopt,KIND=${rk}$)
return
end subroutine stdlib${ii}$_${ri}$orm22
#:endif
#:endfor
pure module subroutine stdlib${ii}$_sdisna( job, m, n, d, sep, info )
!! SDISNA computes the reciprocal condition numbers for the eigenvectors
!! of a real symmetric or complex Hermitian matrix or for the left or
!! right singular vectors of a general m-by-n matrix. The reciprocal
!! condition number is the 'gap' between the corresponding eigenvalue or
!! singular value and the nearest other one.
!! The bound on the error, measured by angle in radians, in the I-th
!! computed vector is given by
!! SLAMCH( 'E' ) * ( ANORM / SEP( I ) )
!! where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed
!! to be smaller than SLAMCH( 'E' )*ANORM in order to limit the size of
!! the error bound.
!! SDISNA may also be used to compute error bounds for eigenvectors of
!! the generalized symmetric definite eigenproblem.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: job
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: m, n
! Array Arguments
real(sp), intent(in) :: d(*)
real(sp), intent(out) :: sep(*)
! =====================================================================
! Local Scalars
logical(lk) :: decr, eigen, incr, left, right, sing
integer(${ik}$) :: i, k
real(sp) :: anorm, eps, newgap, oldgap, safmin, thresh
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
eigen = stdlib_lsame( job, 'E' )
left = stdlib_lsame( job, 'L' )
right = stdlib_lsame( job, 'R' )
sing = left .or. right
if( eigen ) then
k = m
else if( sing ) then
k = min( m, n )
end if
if( .not.eigen .and. .not.sing ) then
info = -1_${ik}$
else if( m<0_${ik}$ ) then
info = -2_${ik}$
else if( k<0_${ik}$ ) then
info = -3_${ik}$
else
incr = .true.
decr = .true.
do i = 1, k - 1
if( incr )incr = incr .and. d( i )<=d( i+1 )
if( decr )decr = decr .and. d( i )>=d( i+1 )
end do
if( sing .and. k>0_${ik}$ ) then
if( incr )incr = incr .and. zero<=d( 1_${ik}$ )
if( decr )decr = decr .and. d( k )>=zero
end if
if( .not.( incr .or. decr ) )info = -4_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SDISNA', -info )
return
end if
! quick return if possible
if( k==0 )return
! compute reciprocal condition numbers
if( k==1_${ik}$ ) then
sep( 1_${ik}$ ) = stdlib${ii}$_slamch( 'O' )
else
oldgap = abs( d( 2_${ik}$ )-d( 1_${ik}$ ) )
sep( 1_${ik}$ ) = oldgap
do i = 2, k - 1
newgap = abs( d( i+1 )-d( i ) )
sep( i ) = min( oldgap, newgap )
oldgap = newgap
end do
sep( k ) = oldgap
end if
if( sing ) then
if( ( left .and. m>n ) .or. ( right .and. m<n ) ) then
if( incr )sep( 1_${ik}$ ) = min( sep( 1_${ik}$ ), d( 1_${ik}$ ) )
if( decr )sep( k ) = min( sep( k ), d( k ) )
end if
end if
! ensure that reciprocal condition numbers are not less than
! threshold, in order to limit the size of the error bound
eps = stdlib${ii}$_slamch( 'E' )
safmin = stdlib${ii}$_slamch( 'S' )
anorm = max( abs( d( 1_${ik}$ ) ), abs( d( k ) ) )
if( anorm==zero ) then
thresh = eps
else
thresh = max( eps*anorm, safmin )
end if
do i = 1, k
sep( i ) = max( sep( i ), thresh )
end do
return
end subroutine stdlib${ii}$_sdisna
pure module subroutine stdlib${ii}$_ddisna( job, m, n, d, sep, info )
!! DDISNA computes the reciprocal condition numbers for the eigenvectors
!! of a real symmetric or complex Hermitian matrix or for the left or
!! right singular vectors of a general m-by-n matrix. The reciprocal
!! condition number is the 'gap' between the corresponding eigenvalue or
!! singular value and the nearest other one.
!! The bound on the error, measured by angle in radians, in the I-th
!! computed vector is given by
!! DLAMCH( 'E' ) * ( ANORM / SEP( I ) )
!! where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed
!! to be smaller than DLAMCH( 'E' )*ANORM in order to limit the size of
!! the error bound.
!! DDISNA may also be used to compute error bounds for eigenvectors of
!! the generalized symmetric definite eigenproblem.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: job
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: m, n
! Array Arguments
real(dp), intent(in) :: d(*)
real(dp), intent(out) :: sep(*)
! =====================================================================
! Local Scalars
logical(lk) :: decr, eigen, incr, left, right, sing
integer(${ik}$) :: i, k
real(dp) :: anorm, eps, newgap, oldgap, safmin, thresh
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
eigen = stdlib_lsame( job, 'E' )
left = stdlib_lsame( job, 'L' )
right = stdlib_lsame( job, 'R' )
sing = left .or. right
if( eigen ) then
k = m
else if( sing ) then
k = min( m, n )
end if
if( .not.eigen .and. .not.sing ) then
info = -1_${ik}$
else if( m<0_${ik}$ ) then
info = -2_${ik}$
else if( k<0_${ik}$ ) then
info = -3_${ik}$
else
incr = .true.
decr = .true.
do i = 1, k - 1
if( incr )incr = incr .and. d( i )<=d( i+1 )
if( decr )decr = decr .and. d( i )>=d( i+1 )
end do
if( sing .and. k>0_${ik}$ ) then
if( incr )incr = incr .and. zero<=d( 1_${ik}$ )
if( decr )decr = decr .and. d( k )>=zero
end if
if( .not.( incr .or. decr ) )info = -4_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DDISNA', -info )
return
end if
! quick return if possible
if( k==0 )return
! compute reciprocal condition numbers
if( k==1_${ik}$ ) then
sep( 1_${ik}$ ) = stdlib${ii}$_dlamch( 'O' )
else
oldgap = abs( d( 2_${ik}$ )-d( 1_${ik}$ ) )
sep( 1_${ik}$ ) = oldgap
do i = 2, k - 1
newgap = abs( d( i+1 )-d( i ) )
sep( i ) = min( oldgap, newgap )
oldgap = newgap
end do
sep( k ) = oldgap
end if
if( sing ) then
if( ( left .and. m>n ) .or. ( right .and. m<n ) ) then
if( incr )sep( 1_${ik}$ ) = min( sep( 1_${ik}$ ), d( 1_${ik}$ ) )
if( decr )sep( k ) = min( sep( k ), d( k ) )
end if
end if
! ensure that reciprocal condition numbers are not less than
! threshold, in order to limit the size of the error bound
eps = stdlib${ii}$_dlamch( 'E' )
safmin = stdlib${ii}$_dlamch( 'S' )
anorm = max( abs( d( 1_${ik}$ ) ), abs( d( k ) ) )
if( anorm==zero ) then
thresh = eps
else
thresh = max( eps*anorm, safmin )
end if
do i = 1, k
sep( i ) = max( sep( i ), thresh )
end do
return
end subroutine stdlib${ii}$_ddisna
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$disna( job, m, n, d, sep, info )
!! DDISNA: computes the reciprocal condition numbers for the eigenvectors
!! of a real symmetric or complex Hermitian matrix or for the left or
!! right singular vectors of a general m-by-n matrix. The reciprocal
!! condition number is the 'gap' between the corresponding eigenvalue or
!! singular value and the nearest other one.
!! The bound on the error, measured by angle in radians, in the I-th
!! computed vector is given by
!! DLAMCH( 'E' ) * ( ANORM / SEP( I ) )
!! where ANORM = 2-norm(A) = max( abs( D(j) ) ). SEP(I) is not allowed
!! to be smaller than DLAMCH( 'E' )*ANORM in order to limit the size of
!! the error bound.
!! DDISNA may also be used to compute error bounds for eigenvectors of
!! the generalized symmetric definite eigenproblem.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: job
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: m, n
! Array Arguments
real(${rk}$), intent(in) :: d(*)
real(${rk}$), intent(out) :: sep(*)
! =====================================================================
! Local Scalars
logical(lk) :: decr, eigen, incr, left, right, sing
integer(${ik}$) :: i, k
real(${rk}$) :: anorm, eps, newgap, oldgap, safmin, thresh
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
eigen = stdlib_lsame( job, 'E' )
left = stdlib_lsame( job, 'L' )
right = stdlib_lsame( job, 'R' )
sing = left .or. right
if( eigen ) then
k = m
else if( sing ) then
k = min( m, n )
end if
if( .not.eigen .and. .not.sing ) then
info = -1_${ik}$
else if( m<0_${ik}$ ) then
info = -2_${ik}$
else if( k<0_${ik}$ ) then
info = -3_${ik}$
else
incr = .true.
decr = .true.
do i = 1, k - 1
if( incr )incr = incr .and. d( i )<=d( i+1 )
if( decr )decr = decr .and. d( i )>=d( i+1 )
end do
if( sing .and. k>0_${ik}$ ) then
if( incr )incr = incr .and. zero<=d( 1_${ik}$ )
if( decr )decr = decr .and. d( k )>=zero
end if
if( .not.( incr .or. decr ) )info = -4_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DDISNA', -info )
return
end if
! quick return if possible
if( k==0 )return
! compute reciprocal condition numbers
if( k==1_${ik}$ ) then
sep( 1_${ik}$ ) = stdlib${ii}$_${ri}$lamch( 'O' )
else
oldgap = abs( d( 2_${ik}$ )-d( 1_${ik}$ ) )
sep( 1_${ik}$ ) = oldgap
do i = 2, k - 1
newgap = abs( d( i+1 )-d( i ) )
sep( i ) = min( oldgap, newgap )
oldgap = newgap
end do
sep( k ) = oldgap
end if
if( sing ) then
if( ( left .and. m>n ) .or. ( right .and. m<n ) ) then
if( incr )sep( 1_${ik}$ ) = min( sep( 1_${ik}$ ), d( 1_${ik}$ ) )
if( decr )sep( k ) = min( sep( k ), d( k ) )
end if
end if
! ensure that reciprocal condition numbers are not less than
! threshold, in order to limit the size of the error bound
eps = stdlib${ii}$_${ri}$lamch( 'E' )
safmin = stdlib${ii}$_${ri}$lamch( 'S' )
anorm = max( abs( d( 1_${ik}$ ) ), abs( d( k ) ) )
if( anorm==zero ) then
thresh = eps
else
thresh = max( eps*anorm, safmin )
end if
do i = 1, k
sep( i ) = max( sep( i ), thresh )
end do
return
end subroutine stdlib${ii}$_${ri}$disna
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slatrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! SLATRD reduces NB rows and columns of a real symmetric matrix A to
!! symmetric tridiagonal form by an orthogonal similarity
!! transformation Q**T * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', SLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', SLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by SSYTRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(sp), intent(inout) :: a(lda,*)
real(sp), intent(out) :: e(*), tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
real(sp) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', i, n-i, -one, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 )&
, ldw, one, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', i, n-i, -one, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 )&
, lda, one, a( 1_${ik}$, i ), 1_${ik}$ )
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
call stdlib${ii}$_slarfg( i-1, a( i-1, i ), a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = a( i-1, i )
a( i-1, i ) = one
! compute w(1:i-1,i)
call stdlib${ii}$_ssymv( 'UPPER', i-1, one, a, lda, a( 1_${ik}$, i ), 1_${ik}$,zero, w( 1_${ik}$, iw ), &
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_sgemv( 'TRANSPOSE', i-1, n-i, one, w( 1_${ik}$, iw+1 ),ldw, a( 1_${ik}$, i ),&
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', i-1, n-i, -one,a( 1_${ik}$, i+1 ), lda, w( i+1,&
iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'TRANSPOSE', i-1, n-i, one, a( 1_${ik}$, i+1 ),lda, a( 1_${ik}$, i ), &
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', i-1, n-i, -one,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_sscal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -half*tau( i-1 )*stdlib${ii}$_sdot( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_saxpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
do i = 1, nb
! update a(i:n,i)
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', n-i+1, i-1, -one, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, one, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', n-i+1, i-1, -one, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, one, a( i, i ), 1_${ik}$ )
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
call stdlib${ii}$_slarfg( n-i, a( i+1, i ), a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = a( i+1, i )
a( i+1, i ) = one
! compute w(i+1:n,i)
call stdlib${ii}$_ssymv( 'LOWER', n-i, one, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, zero,&
w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'TRANSPOSE', n-i, i-1, one, w( i+1, 1_${ik}$ ), ldw,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', n-i, i-1, -one, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'TRANSPOSE', n-i, i-1, one, a( i+1, 1_${ik}$ ), lda,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_sgemv( 'NO TRANSPOSE', n-i, i-1, -one, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_sscal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -half*tau( i )*stdlib${ii}$_sdot( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_saxpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do
end if
return
end subroutine stdlib${ii}$_slatrd
pure module subroutine stdlib${ii}$_dlatrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! DLATRD reduces NB rows and columns of a real symmetric matrix A to
!! symmetric tridiagonal form by an orthogonal similarity
!! transformation Q**T * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', DLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', DLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by DSYTRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(dp), intent(inout) :: a(lda,*)
real(dp), intent(out) :: e(*), tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
real(dp) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', i, n-i, -one, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 )&
, ldw, one, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', i, n-i, -one, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 )&
, lda, one, a( 1_${ik}$, i ), 1_${ik}$ )
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
call stdlib${ii}$_dlarfg( i-1, a( i-1, i ), a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = a( i-1, i )
a( i-1, i ) = one
! compute w(1:i-1,i)
call stdlib${ii}$_dsymv( 'UPPER', i-1, one, a, lda, a( 1_${ik}$, i ), 1_${ik}$,zero, w( 1_${ik}$, iw ), &
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_dgemv( 'TRANSPOSE', i-1, n-i, one, w( 1_${ik}$, iw+1 ),ldw, a( 1_${ik}$, i ),&
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', i-1, n-i, -one,a( 1_${ik}$, i+1 ), lda, w( i+1,&
iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'TRANSPOSE', i-1, n-i, one, a( 1_${ik}$, i+1 ),lda, a( 1_${ik}$, i ), &
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', i-1, n-i, -one,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_dscal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -half*tau( i-1 )*stdlib${ii}$_ddot( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_daxpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
do i = 1, nb
! update a(i:n,i)
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', n-i+1, i-1, -one, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, one, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', n-i+1, i-1, -one, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, one, a( i, i ), 1_${ik}$ )
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
call stdlib${ii}$_dlarfg( n-i, a( i+1, i ), a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = a( i+1, i )
a( i+1, i ) = one
! compute w(i+1:n,i)
call stdlib${ii}$_dsymv( 'LOWER', n-i, one, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, zero,&
w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'TRANSPOSE', n-i, i-1, one, w( i+1, 1_${ik}$ ), ldw,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', n-i, i-1, -one, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'TRANSPOSE', n-i, i-1, one, a( i+1, 1_${ik}$ ), lda,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_dgemv( 'NO TRANSPOSE', n-i, i-1, -one, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_dscal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -half*tau( i )*stdlib${ii}$_ddot( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_daxpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do
end if
return
end subroutine stdlib${ii}$_dlatrd
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$latrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! DLATRD: reduces NB rows and columns of a real symmetric matrix A to
!! symmetric tridiagonal form by an orthogonal similarity
!! transformation Q**T * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', DLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', DLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by DSYTRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(${rk}$), intent(inout) :: a(lda,*)
real(${rk}$), intent(out) :: e(*), tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
real(${rk}$) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', i, n-i, -one, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 )&
, ldw, one, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', i, n-i, -one, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 )&
, lda, one, a( 1_${ik}$, i ), 1_${ik}$ )
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
call stdlib${ii}$_${ri}$larfg( i-1, a( i-1, i ), a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = a( i-1, i )
a( i-1, i ) = one
! compute w(1:i-1,i)
call stdlib${ii}$_${ri}$symv( 'UPPER', i-1, one, a, lda, a( 1_${ik}$, i ), 1_${ik}$,zero, w( 1_${ik}$, iw ), &
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_${ri}$gemv( 'TRANSPOSE', i-1, n-i, one, w( 1_${ik}$, iw+1 ),ldw, a( 1_${ik}$, i ),&
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', i-1, n-i, -one,a( 1_${ik}$, i+1 ), lda, w( i+1,&
iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'TRANSPOSE', i-1, n-i, one, a( 1_${ik}$, i+1 ),lda, a( 1_${ik}$, i ), &
1_${ik}$, zero, w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', i-1, n-i, -one,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, one,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_${ri}$scal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -half*tau( i-1 )*stdlib${ii}$_${ri}$dot( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$axpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
do i = 1, nb
! update a(i:n,i)
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', n-i+1, i-1, -one, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, one, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', n-i+1, i-1, -one, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, one, a( i, i ), 1_${ik}$ )
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
call stdlib${ii}$_${ri}$larfg( n-i, a( i+1, i ), a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = a( i+1, i )
a( i+1, i ) = one
! compute w(i+1:n,i)
call stdlib${ii}$_${ri}$symv( 'LOWER', n-i, one, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, zero,&
w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'TRANSPOSE', n-i, i-1, one, w( i+1, 1_${ik}$ ), ldw,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', n-i, i-1, -one, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'TRANSPOSE', n-i, i-1, one, a( i+1, 1_${ik}$ ), lda,a( i+1, i ), &
1_${ik}$, zero, w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$gemv( 'NO TRANSPOSE', n-i, i-1, -one, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i ),&
1_${ik}$, one, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$scal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -half*tau( i )*stdlib${ii}$_${ri}$dot( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ri}$axpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do
end if
return
end subroutine stdlib${ii}$_${ri}$latrd
#:endif
#:endfor
pure module subroutine stdlib${ii}$_clatrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! CLATRD reduces NB rows and columns of a complex Hermitian matrix A to
!! Hermitian tridiagonal form by a unitary similarity
!! transformation Q**H * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', CLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', CLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by CHETRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(sp), intent(out) :: e(*)
complex(sp), intent(inout) :: a(lda,*)
complex(sp), intent(out) :: tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
complex(sp) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
a( i, i ) = real( a( i, i ),KIND=sp)
call stdlib${ii}$_clacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', i, n-i, -cone, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 &
), ldw, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_clacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_clacgv( n-i, a( i, i+1 ), lda )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', i, n-i, -cone, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 &
), lda, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_clacgv( n-i, a( i, i+1 ), lda )
a( i, i ) = real( a( i, i ),KIND=sp)
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
alpha = a( i-1, i )
call stdlib${ii}$_clarfg( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = real( alpha,KIND=sp)
a( i-1, i ) = cone
! compute w(1:i-1,i)
call stdlib${ii}$_chemv( 'UPPER', i-1, cone, a, lda, a( 1_${ik}$, i ), 1_${ik}$,czero, w( 1_${ik}$, iw ),&
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_cgemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,w( 1_${ik}$, iw+1 ), ldw,&
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', i-1, n-i, -cone,a( 1_${ik}$, i+1 ), lda, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,a( 1_${ik}$, i+1 ), lda, &
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', i-1, n-i, -cone,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_cscal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -chalf*tau( i-1 )*stdlib${ii}$_cdotc( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_caxpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
loop_20: do i = 1, nb
! update a(i:n,i)
a( i, i ) = real( a( i, i ),KIND=sp)
call stdlib${ii}$_clacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_clacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_clacgv( i-1, a( i, 1_${ik}$ ), lda )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_clacgv( i-1, a( i, 1_${ik}$ ), lda )
a( i, i ) = real( a( i, i ),KIND=sp)
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
alpha = a( i+1, i )
call stdlib${ii}$_clarfg( n-i, alpha, a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = real( alpha,KIND=sp)
a( i+1, i ) = cone
! compute w(i+1:n,i)
call stdlib${ii}$_chemv( 'LOWER', n-i, cone, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, &
czero, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,w( i+1, 1_${ik}$ ), ldw, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', n-i, i-1, -cone, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,a( i+1, 1_${ik}$ ), lda, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_cgemv( 'NO TRANSPOSE', n-i, i-1, -cone, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_cscal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -chalf*tau( i )*stdlib${ii}$_cdotc( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_caxpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_clatrd
pure module subroutine stdlib${ii}$_zlatrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! ZLATRD reduces NB rows and columns of a complex Hermitian matrix A to
!! Hermitian tridiagonal form by a unitary similarity
!! transformation Q**H * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', ZLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', ZLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by ZHETRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(dp), intent(out) :: e(*)
complex(dp), intent(inout) :: a(lda,*)
complex(dp), intent(out) :: tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
complex(dp) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
a( i, i ) = real( a( i, i ),KIND=dp)
call stdlib${ii}$_zlacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', i, n-i, -cone, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 &
), ldw, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_zlacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_zlacgv( n-i, a( i, i+1 ), lda )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', i, n-i, -cone, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 &
), lda, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_zlacgv( n-i, a( i, i+1 ), lda )
a( i, i ) = real( a( i, i ),KIND=dp)
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
alpha = a( i-1, i )
call stdlib${ii}$_zlarfg( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = real( alpha,KIND=dp)
a( i-1, i ) = cone
! compute w(1:i-1,i)
call stdlib${ii}$_zhemv( 'UPPER', i-1, cone, a, lda, a( 1_${ik}$, i ), 1_${ik}$,czero, w( 1_${ik}$, iw ),&
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_zgemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,w( 1_${ik}$, iw+1 ), ldw,&
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', i-1, n-i, -cone,a( 1_${ik}$, i+1 ), lda, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,a( 1_${ik}$, i+1 ), lda, &
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', i-1, n-i, -cone,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_zscal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -chalf*tau( i-1 )*stdlib${ii}$_zdotc( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_zaxpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
loop_20: do i = 1, nb
! update a(i:n,i)
a( i, i ) = real( a( i, i ),KIND=dp)
call stdlib${ii}$_zlacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_zlacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_zlacgv( i-1, a( i, 1_${ik}$ ), lda )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_zlacgv( i-1, a( i, 1_${ik}$ ), lda )
a( i, i ) = real( a( i, i ),KIND=dp)
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
alpha = a( i+1, i )
call stdlib${ii}$_zlarfg( n-i, alpha, a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = real( alpha,KIND=dp)
a( i+1, i ) = cone
! compute w(i+1:n,i)
call stdlib${ii}$_zhemv( 'LOWER', n-i, cone, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, &
czero, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,w( i+1, 1_${ik}$ ), ldw, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', n-i, i-1, -cone, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,a( i+1, 1_${ik}$ ), lda, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_zgemv( 'NO TRANSPOSE', n-i, i-1, -cone, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_zscal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -chalf*tau( i )*stdlib${ii}$_zdotc( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_zaxpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_zlatrd
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$latrd( uplo, n, nb, a, lda, e, tau, w, ldw )
!! ZLATRD: reduces NB rows and columns of a complex Hermitian matrix A to
!! Hermitian tridiagonal form by a unitary similarity
!! transformation Q**H * A * Q, and returns the matrices V and W which are
!! needed to apply the transformation to the unreduced part of A.
!! If UPLO = 'U', ZLATRD reduces the last NB rows and columns of a
!! matrix, of which the upper triangle is supplied;
!! if UPLO = 'L', ZLATRD reduces the first NB rows and columns of a
!! matrix, of which the lower triangle is supplied.
!! This is an auxiliary routine called by ZHETRD.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(in) :: lda, ldw, n, nb
! Array Arguments
real(${ck}$), intent(out) :: e(*)
complex(${ck}$), intent(inout) :: a(lda,*)
complex(${ck}$), intent(out) :: tau(*), w(ldw,*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: i, iw
complex(${ck}$) :: alpha
! Intrinsic Functions
! Executable Statements
! quick return if possible
if( n<=0 )return
if( stdlib_lsame( uplo, 'U' ) ) then
! reduce last nb columns of upper triangle
loop_10: do i = n, n - nb + 1, -1
iw = i - n + nb
if( i<n ) then
! update a(1:i,i)
a( i, i ) = real( a( i, i ),KIND=${ck}$)
call stdlib${ii}$_${ci}$lacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', i, n-i, -cone, a( 1_${ik}$, i+1 ),lda, w( i, iw+1 &
), ldw, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$lacgv( n-i, w( i, iw+1 ), ldw )
call stdlib${ii}$_${ci}$lacgv( n-i, a( i, i+1 ), lda )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', i, n-i, -cone, w( 1_${ik}$, iw+1 ),ldw, a( i, i+1 &
), lda, cone, a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$lacgv( n-i, a( i, i+1 ), lda )
a( i, i ) = real( a( i, i ),KIND=${ck}$)
end if
if( i>1_${ik}$ ) then
! generate elementary reflector h(i) to annihilate
! a(1:i-2,i)
alpha = a( i-1, i )
call stdlib${ii}$_${ci}$larfg( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, tau( i-1 ) )
e( i-1 ) = real( alpha,KIND=${ck}$)
a( i-1, i ) = cone
! compute w(1:i-1,i)
call stdlib${ii}$_${ci}$hemv( 'UPPER', i-1, cone, a, lda, a( 1_${ik}$, i ), 1_${ik}$,czero, w( 1_${ik}$, iw ),&
1_${ik}$ )
if( i<n ) then
call stdlib${ii}$_${ci}$gemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,w( 1_${ik}$, iw+1 ), ldw,&
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', i-1, n-i, -cone,a( 1_${ik}$, i+1 ), lda, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'CONJUGATE TRANSPOSE', i-1, n-i, cone,a( 1_${ik}$, i+1 ), lda, &
a( 1_${ik}$, i ), 1_${ik}$, czero,w( i+1, iw ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', i-1, n-i, -cone,w( 1_${ik}$, iw+1 ), ldw, w( i+&
1_${ik}$, iw ), 1_${ik}$, cone,w( 1_${ik}$, iw ), 1_${ik}$ )
end if
call stdlib${ii}$_${ci}$scal( i-1, tau( i-1 ), w( 1_${ik}$, iw ), 1_${ik}$ )
alpha = -chalf*tau( i-1 )*stdlib${ii}$_${ci}$dotc( i-1, w( 1_${ik}$, iw ), 1_${ik}$,a( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$axpy( i-1, alpha, a( 1_${ik}$, i ), 1_${ik}$, w( 1_${ik}$, iw ), 1_${ik}$ )
end if
end do loop_10
else
! reduce first nb columns of lower triangle
loop_20: do i = 1, nb
! update a(i:n,i)
a( i, i ) = real( a( i, i ),KIND=${ck}$)
call stdlib${ii}$_${ci}$lacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, a( i, 1_${ik}$ ),lda, w( i, 1_${ik}$ ), &
ldw, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$lacgv( i-1, w( i, 1_${ik}$ ), ldw )
call stdlib${ii}$_${ci}$lacgv( i-1, a( i, 1_${ik}$ ), lda )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', n-i+1, i-1, -cone, w( i, 1_${ik}$ ),ldw, a( i, 1_${ik}$ ), &
lda, cone, a( i, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$lacgv( i-1, a( i, 1_${ik}$ ), lda )
a( i, i ) = real( a( i, i ),KIND=${ck}$)
if( i<n ) then
! generate elementary reflector h(i) to annihilate
! a(i+2:n,i)
alpha = a( i+1, i )
call stdlib${ii}$_${ci}$larfg( n-i, alpha, a( min( i+2, n ), i ), 1_${ik}$,tau( i ) )
e( i ) = real( alpha,KIND=${ck}$)
a( i+1, i ) = cone
! compute w(i+1:n,i)
call stdlib${ii}$_${ci}$hemv( 'LOWER', n-i, cone, a( i+1, i+1 ), lda,a( i+1, i ), 1_${ik}$, &
czero, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,w( i+1, 1_${ik}$ ), ldw, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', n-i, i-1, -cone, a( i+1, 1_${ik}$ ),lda, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'CONJUGATE TRANSPOSE', n-i, i-1, cone,a( i+1, 1_${ik}$ ), lda, a( &
i+1, i ), 1_${ik}$, czero,w( 1_${ik}$, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$gemv( 'NO TRANSPOSE', n-i, i-1, -cone, w( i+1, 1_${ik}$ ),ldw, w( 1_${ik}$, i )&
, 1_${ik}$, cone, w( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$scal( n-i, tau( i ), w( i+1, i ), 1_${ik}$ )
alpha = -chalf*tau( i )*stdlib${ii}$_${ci}$dotc( n-i, w( i+1, i ), 1_${ik}$,a( i+1, i ), 1_${ik}$ )
call stdlib${ii}$_${ci}$axpy( n-i, alpha, a( i+1, i ), 1_${ik}$, w( i+1, i ), 1_${ik}$ )
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_${ci}$latrd
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slae2( a, b, c, rt1, rt2 )
!! SLAE2 computes the eigenvalues of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, and RT2
!! is the eigenvalue of smaller absolute value.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(sp), intent(in) :: a, b, c
real(sp), intent(out) :: rt1, rt2
! =====================================================================
! Local Scalars
real(sp) :: ab, acmn, acmx, adf, df, rt, sm, tb
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
end if
return
end subroutine stdlib${ii}$_slae2
pure module subroutine stdlib${ii}$_dlae2( a, b, c, rt1, rt2 )
!! DLAE2 computes the eigenvalues of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, and RT2
!! is the eigenvalue of smaller absolute value.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(dp), intent(in) :: a, b, c
real(dp), intent(out) :: rt1, rt2
! =====================================================================
! Local Scalars
real(dp) :: ab, acmn, acmx, adf, df, rt, sm, tb
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
end if
return
end subroutine stdlib${ii}$_dlae2
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$lae2( a, b, c, rt1, rt2 )
!! DLAE2: computes the eigenvalues of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, and RT2
!! is the eigenvalue of smaller absolute value.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(${rk}$), intent(in) :: a, b, c
real(${rk}$), intent(out) :: rt1, rt2
! =====================================================================
! Local Scalars
real(${rk}$) :: ab, acmn, acmx, adf, df, rt, sm, tb
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
end if
return
end subroutine stdlib${ii}$_${ri}$lae2
#:endif
#:endfor
pure module subroutine stdlib${ii}$_claesy( a, b, c, rt1, rt2, evscal, cs1, sn1 )
!! CLAESY computes the eigendecomposition of a 2-by-2 symmetric matrix
!! ( ( A, B );( B, C ) )
!! provided the norm of the matrix of eigenvectors is larger than
!! some threshold value.
!! RT1 is the eigenvalue of larger absolute value, and RT2 of
!! smaller absolute value. If the eigenvectors are computed, then
!! on return ( CS1, SN1 ) is the unit eigenvector for RT1, hence
!! [ CS1 SN1 ] . [ A B ] . [ CS1 -SN1 ] = [ RT1 0 ]
!! [ -SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
complex(sp), intent(in) :: a, b, c
complex(sp), intent(out) :: cs1, evscal, rt1, rt2, sn1
! =====================================================================
! Parameters
real(sp), parameter :: thresh = 0.1_sp
! Local Scalars
real(sp) :: babs, evnorm, tabs, z
complex(sp) :: s, t, tmp
! Intrinsic Functions
! Executable Statements
! special case: the matrix is actually diagonal.
! to avoid divide by zero later, we treat this case separately.
if( abs( b )==zero ) then
rt1 = a
rt2 = c
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
cs1 = zero
sn1 = one
else
cs1 = one
sn1 = zero
end if
else
! compute the eigenvalues and eigenvectors.
! the characteristic equation is
! lambda **2 - (a+c) lambda + (a*c - b*b)
! and we solve it using the quadratic formula.
s = ( a+c )*half
t = ( a-c )*half
! take the square root carefully to avoid over/under flow.
babs = abs( b )
tabs = abs( t )
z = max( babs, tabs )
if( z>zero )t = z*sqrt( ( t / z )**2_${ik}$+( b / z )**2_${ik}$ )
! compute the two eigenvalues. rt1 and rt2 are exchanged
! if necessary so that rt1 will have the greater magnitude.
rt1 = s + t
rt2 = s - t
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
end if
! choose cs1 = 1 and sn1 to satisfy the first equation, then
! scale the components of this eigenvector so that the matrix
! of eigenvectors x satisfies x * x**t = i . (no scaling is
! done if the norm of the eigenvalue matrix is less than thresh.)
sn1 = ( rt1-a ) / b
tabs = abs( sn1 )
if( tabs>one ) then
t = tabs*sqrt( ( one / tabs )**2_${ik}$+( sn1 / tabs )**2_${ik}$ )
else
t = sqrt( cone+sn1*sn1 )
end if
evnorm = abs( t )
if( evnorm>=thresh ) then
evscal = cone / t
cs1 = evscal
sn1 = sn1*evscal
else
evscal = zero
end if
end if
return
end subroutine stdlib${ii}$_claesy
pure module subroutine stdlib${ii}$_zlaesy( a, b, c, rt1, rt2, evscal, cs1, sn1 )
!! ZLAESY computes the eigendecomposition of a 2-by-2 symmetric matrix
!! ( ( A, B );( B, C ) )
!! provided the norm of the matrix of eigenvectors is larger than
!! some threshold value.
!! RT1 is the eigenvalue of larger absolute value, and RT2 of
!! smaller absolute value. If the eigenvectors are computed, then
!! on return ( CS1, SN1 ) is the unit eigenvector for RT1, hence
!! [ CS1 SN1 ] . [ A B ] . [ CS1 -SN1 ] = [ RT1 0 ]
!! [ -SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
complex(dp), intent(in) :: a, b, c
complex(dp), intent(out) :: cs1, evscal, rt1, rt2, sn1
! =====================================================================
! Parameters
real(dp), parameter :: thresh = 0.1_dp
! Local Scalars
real(dp) :: babs, evnorm, tabs, z
complex(dp) :: s, t, tmp
! Intrinsic Functions
! Executable Statements
! special case: the matrix is actually diagonal.
! to avoid divide by zero later, we treat this case separately.
if( abs( b )==zero ) then
rt1 = a
rt2 = c
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
cs1 = zero
sn1 = one
else
cs1 = one
sn1 = zero
end if
else
! compute the eigenvalues and eigenvectors.
! the characteristic equation is
! lambda **2 - (a+c) lambda + (a*c - b*b)
! and we solve it using the quadratic formula.
s = ( a+c )*half
t = ( a-c )*half
! take the square root carefully to avoid over/under flow.
babs = abs( b )
tabs = abs( t )
z = max( babs, tabs )
if( z>zero )t = z*sqrt( ( t / z )**2_${ik}$+( b / z )**2_${ik}$ )
! compute the two eigenvalues. rt1 and rt2 are exchanged
! if necessary so that rt1 will have the greater magnitude.
rt1 = s + t
rt2 = s - t
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
end if
! choose cs1 = 1 and sn1 to satisfy the first equation, then
! scale the components of this eigenvector so that the matrix
! of eigenvectors x satisfies x * x**t = i . (no scaling is
! done if the norm of the eigenvalue matrix is less than thresh.)
sn1 = ( rt1-a ) / b
tabs = abs( sn1 )
if( tabs>one ) then
t = tabs*sqrt( ( one / tabs )**2_${ik}$+( sn1 / tabs )**2_${ik}$ )
else
t = sqrt( cone+sn1*sn1 )
end if
evnorm = abs( t )
if( evnorm>=thresh ) then
evscal = cone / t
cs1 = evscal
sn1 = sn1*evscal
else
evscal = zero
end if
end if
return
end subroutine stdlib${ii}$_zlaesy
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$laesy( a, b, c, rt1, rt2, evscal, cs1, sn1 )
!! ZLAESY: computes the eigendecomposition of a 2-by-2 symmetric matrix
!! ( ( A, B );( B, C ) )
!! provided the norm of the matrix of eigenvectors is larger than
!! some threshold value.
!! RT1 is the eigenvalue of larger absolute value, and RT2 of
!! smaller absolute value. If the eigenvectors are computed, then
!! on return ( CS1, SN1 ) is the unit eigenvector for RT1, hence
!! [ CS1 SN1 ] . [ A B ] . [ CS1 -SN1 ] = [ RT1 0 ]
!! [ -SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
complex(${ck}$), intent(in) :: a, b, c
complex(${ck}$), intent(out) :: cs1, evscal, rt1, rt2, sn1
! =====================================================================
! Parameters
real(${ck}$), parameter :: thresh = 0.1_${ck}$
! Local Scalars
real(${ck}$) :: babs, evnorm, tabs, z
complex(${ck}$) :: s, t, tmp
! Intrinsic Functions
! Executable Statements
! special case: the matrix is actually diagonal.
! to avoid divide by zero later, we treat this case separately.
if( abs( b )==zero ) then
rt1 = a
rt2 = c
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
cs1 = zero
sn1 = one
else
cs1 = one
sn1 = zero
end if
else
! compute the eigenvalues and eigenvectors.
! the characteristic equation is
! lambda **2 - (a+c) lambda + (a*c - b*b)
! and we solve it using the quadratic formula.
s = ( a+c )*half
t = ( a-c )*half
! take the square root carefully to avoid over/under flow.
babs = abs( b )
tabs = abs( t )
z = max( babs, tabs )
if( z>zero )t = z*sqrt( ( t / z )**2_${ik}$+( b / z )**2_${ik}$ )
! compute the two eigenvalues. rt1 and rt2 are exchanged
! if necessary so that rt1 will have the greater magnitude.
rt1 = s + t
rt2 = s - t
if( abs( rt1 )<abs( rt2 ) ) then
tmp = rt1
rt1 = rt2
rt2 = tmp
end if
! choose cs1 = 1 and sn1 to satisfy the first equation, then
! scale the components of this eigenvector so that the matrix
! of eigenvectors x satisfies x * x**t = i . (no scaling is
! done if the norm of the eigenvalue matrix is less than thresh.)
sn1 = ( rt1-a ) / b
tabs = abs( sn1 )
if( tabs>one ) then
t = tabs*sqrt( ( one / tabs )**2_${ik}$+( sn1 / tabs )**2_${ik}$ )
else
t = sqrt( cone+sn1*sn1 )
end if
evnorm = abs( t )
if( evnorm>=thresh ) then
evscal = cone / t
cs1 = evscal
sn1 = sn1*evscal
else
evscal = zero
end if
end if
return
end subroutine stdlib${ii}$_${ci}$laesy
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slaev2( a, b, c, rt1, rt2, cs1, sn1 )
!! SLAEV2 computes the eigendecomposition of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 SN1 ] [ A B ] [ CS1 -SN1 ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(sp), intent(in) :: a, b, c
real(sp), intent(out) :: cs1, rt1, rt2, sn1
! =====================================================================
! Local Scalars
integer(${ik}$) :: sgn1, sgn2
real(sp) :: ab, acmn, acmx, acs, adf, cs, ct, df, rt, sm, tb, tn
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
sgn1 = -1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
sgn1 = 1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
sgn1 = 1_${ik}$
end if
! compute the eigenvector
if( df>=zero ) then
cs = df + rt
sgn2 = 1_${ik}$
else
cs = df - rt
sgn2 = -1_${ik}$
end if
acs = abs( cs )
if( acs>ab ) then
ct = -tb / cs
sn1 = one / sqrt( one+ct*ct )
cs1 = ct*sn1
else
if( ab==zero ) then
cs1 = one
sn1 = zero
else
tn = -cs / tb
cs1 = one / sqrt( one+tn*tn )
sn1 = tn*cs1
end if
end if
if( sgn1==sgn2 ) then
tn = cs1
cs1 = -sn1
sn1 = tn
end if
return
end subroutine stdlib${ii}$_slaev2
pure module subroutine stdlib${ii}$_dlaev2( a, b, c, rt1, rt2, cs1, sn1 )
!! DLAEV2 computes the eigendecomposition of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 SN1 ] [ A B ] [ CS1 -SN1 ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(dp), intent(in) :: a, b, c
real(dp), intent(out) :: cs1, rt1, rt2, sn1
! =====================================================================
! Local Scalars
integer(${ik}$) :: sgn1, sgn2
real(dp) :: ab, acmn, acmx, acs, adf, cs, ct, df, rt, sm, tb, tn
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
sgn1 = -1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
sgn1 = 1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
sgn1 = 1_${ik}$
end if
! compute the eigenvector
if( df>=zero ) then
cs = df + rt
sgn2 = 1_${ik}$
else
cs = df - rt
sgn2 = -1_${ik}$
end if
acs = abs( cs )
if( acs>ab ) then
ct = -tb / cs
sn1 = one / sqrt( one+ct*ct )
cs1 = ct*sn1
else
if( ab==zero ) then
cs1 = one
sn1 = zero
else
tn = -cs / tb
cs1 = one / sqrt( one+tn*tn )
sn1 = tn*cs1
end if
end if
if( sgn1==sgn2 ) then
tn = cs1
cs1 = -sn1
sn1 = tn
end if
return
end subroutine stdlib${ii}$_dlaev2
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$laev2( a, b, c, rt1, rt2, cs1, sn1 )
!! DLAEV2: computes the eigendecomposition of a 2-by-2 symmetric matrix
!! [ A B ]
!! [ B C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 SN1 ] [ A B ] [ CS1 -SN1 ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(${rk}$), intent(in) :: a, b, c
real(${rk}$), intent(out) :: cs1, rt1, rt2, sn1
! =====================================================================
! Local Scalars
integer(${ik}$) :: sgn1, sgn2
real(${rk}$) :: ab, acmn, acmx, acs, adf, cs, ct, df, rt, sm, tb, tn
! Intrinsic Functions
! Executable Statements
! compute the eigenvalues
sm = a + c
df = a - c
adf = abs( df )
tb = b + b
ab = abs( tb )
if( abs( a )>abs( c ) ) then
acmx = a
acmn = c
else
acmx = c
acmn = a
end if
if( adf>ab ) then
rt = adf*sqrt( one+( ab / adf )**2_${ik}$ )
else if( adf<ab ) then
rt = ab*sqrt( one+( adf / ab )**2_${ik}$ )
else
! includes case ab=adf=0
rt = ab*sqrt( two )
end if
if( sm<zero ) then
rt1 = half*( sm-rt )
sgn1 = -1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else if( sm>zero ) then
rt1 = half*( sm+rt )
sgn1 = 1_${ik}$
! order of execution important.
! to get fully accurate smaller eigenvalue,
! next line needs to be executed in higher precision.
rt2 = ( acmx / rt1 )*acmn - ( b / rt1 )*b
else
! includes case rt1 = rt2 = 0
rt1 = half*rt
rt2 = -half*rt
sgn1 = 1_${ik}$
end if
! compute the eigenvector
if( df>=zero ) then
cs = df + rt
sgn2 = 1_${ik}$
else
cs = df - rt
sgn2 = -1_${ik}$
end if
acs = abs( cs )
if( acs>ab ) then
ct = -tb / cs
sn1 = one / sqrt( one+ct*ct )
cs1 = ct*sn1
else
if( ab==zero ) then
cs1 = one
sn1 = zero
else
tn = -cs / tb
cs1 = one / sqrt( one+tn*tn )
sn1 = tn*cs1
end if
end if
if( sgn1==sgn2 ) then
tn = cs1
cs1 = -sn1
sn1 = tn
end if
return
end subroutine stdlib${ii}$_${ri}$laev2
#:endif
#:endfor
pure module subroutine stdlib${ii}$_claev2( a, b, c, rt1, rt2, cs1, sn1 )
!! CLAEV2 computes the eigendecomposition of a 2-by-2 Hermitian matrix
!! [ A B ]
!! [ CONJG(B) C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 CONJG(SN1) ] [ A B ] [ CS1 -CONJG(SN1) ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ CONJG(B) C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(sp), intent(out) :: cs1, rt1, rt2
complex(sp), intent(in) :: a, b, c
complex(sp), intent(out) :: sn1
! =====================================================================
! Local Scalars
real(sp) :: t
complex(sp) :: w
! Intrinsic Functions
! Executable Statements
if( abs( b )==zero ) then
w = one
else
w = conjg( b ) / abs( b )
end if
call stdlib${ii}$_slaev2( real( a,KIND=sp), abs( b ), real( c,KIND=sp), rt1, rt2, cs1, t )
sn1 = w*t
return
end subroutine stdlib${ii}$_claev2
pure module subroutine stdlib${ii}$_zlaev2( a, b, c, rt1, rt2, cs1, sn1 )
!! ZLAEV2 computes the eigendecomposition of a 2-by-2 Hermitian matrix
!! [ A B ]
!! [ CONJG(B) C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 CONJG(SN1) ] [ A B ] [ CS1 -CONJG(SN1) ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ CONJG(B) C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(dp), intent(out) :: cs1, rt1, rt2
complex(dp), intent(in) :: a, b, c
complex(dp), intent(out) :: sn1
! =====================================================================
! Local Scalars
real(dp) :: t
complex(dp) :: w
! Intrinsic Functions
! Executable Statements
if( abs( b )==zero ) then
w = one
else
w = conjg( b ) / abs( b )
end if
call stdlib${ii}$_dlaev2( real( a,KIND=dp), abs( b ), real( c,KIND=dp), rt1, rt2, cs1, t )
sn1 = w*t
return
end subroutine stdlib${ii}$_zlaev2
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$laev2( a, b, c, rt1, rt2, cs1, sn1 )
!! ZLAEV2: computes the eigendecomposition of a 2-by-2 Hermitian matrix
!! [ A B ]
!! [ CONJG(B) C ].
!! On return, RT1 is the eigenvalue of larger absolute value, RT2 is the
!! eigenvalue of smaller absolute value, and (CS1,SN1) is the unit right
!! eigenvector for RT1, giving the decomposition
!! [ CS1 CONJG(SN1) ] [ A B ] [ CS1 -CONJG(SN1) ] = [ RT1 0 ]
!! [-SN1 CS1 ] [ CONJG(B) C ] [ SN1 CS1 ] [ 0 RT2 ].
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
real(${ck}$), intent(out) :: cs1, rt1, rt2
complex(${ck}$), intent(in) :: a, b, c
complex(${ck}$), intent(out) :: sn1
! =====================================================================
! Local Scalars
real(${ck}$) :: t
complex(${ck}$) :: w
! Intrinsic Functions
! Executable Statements
if( abs( b )==zero ) then
w = one
else
w = conjg( b ) / abs( b )
end if
call stdlib${ii}$_${c2ri(ci)}$laev2( real( a,KIND=${ck}$), abs( b ), real( c,KIND=${ck}$), rt1, rt2, cs1, t )
sn1 = w*t
return
end subroutine stdlib${ii}$_${ci}$laev2
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slagtf( n, a, lambda, b, c, tol, d, in, info )
!! SLAGTF factorizes the matrix (T - lambda*I), where T is an n by n
!! tridiagonal matrix and lambda is a scalar, as
!! T - lambda*I = PLU,
!! where P is a permutation matrix, L is a unit lower tridiagonal matrix
!! with at most one non-zero sub-diagonal elements per column and U is
!! an upper triangular matrix with at most two non-zero super-diagonal
!! elements per column.
!! The factorization is obtained by Gaussian elimination with partial
!! pivoting and implicit row scaling.
!! The parameter LAMBDA is included in the routine so that SLAGTF may
!! be used, in conjunction with SLAGTS, to obtain eigenvectors of T by
!! inverse iteration.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
real(sp), intent(in) :: lambda, tol
! Array Arguments
integer(${ik}$), intent(out) :: in(*)
real(sp), intent(inout) :: a(*), b(*), c(*)
real(sp), intent(out) :: d(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(sp) :: eps, mult, piv1, piv2, scale1, scale2, temp, tl
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( n<0_${ik}$ ) then
info = -1_${ik}$
call stdlib${ii}$_xerbla( 'SLAGTF', -info )
return
end if
if( n==0 )return
a( 1_${ik}$ ) = a( 1_${ik}$ ) - lambda
in( n ) = 0_${ik}$
if( n==1_${ik}$ ) then
if( a( 1_${ik}$ )==zero )in( 1_${ik}$ ) = 1_${ik}$
return
end if
eps = stdlib${ii}$_slamch( 'EPSILON' )
tl = max( tol, eps )
scale1 = abs( a( 1_${ik}$ ) ) + abs( b( 1_${ik}$ ) )
loop_10: do k = 1, n - 1
a( k+1 ) = a( k+1 ) - lambda
scale2 = abs( c( k ) ) + abs( a( k+1 ) )
if( k<( n-1 ) )scale2 = scale2 + abs( b( k+1 ) )
if( a( k )==zero ) then
piv1 = zero
else
piv1 = abs( a( k ) ) / scale1
end if
if( c( k )==zero ) then
in( k ) = 0_${ik}$
piv2 = zero
scale1 = scale2
if( k<( n-1 ) )d( k ) = zero
else
piv2 = abs( c( k ) ) / scale2
if( piv2<=piv1 ) then
in( k ) = 0_${ik}$
scale1 = scale2
c( k ) = c( k ) / a( k )
a( k+1 ) = a( k+1 ) - c( k )*b( k )
if( k<( n-1 ) )d( k ) = zero
else
in( k ) = 1_${ik}$
mult = a( k ) / c( k )
a( k ) = c( k )
temp = a( k+1 )
a( k+1 ) = b( k ) - mult*temp
if( k<( n-1 ) ) then
d( k ) = b( k+1 )
b( k+1 ) = -mult*d( k )
end if
b( k ) = temp
c( k ) = mult
end if
end if
if( ( max( piv1, piv2 )<=tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = k
end do loop_10
if( ( abs( a( n ) )<=scale1*tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = n
return
end subroutine stdlib${ii}$_slagtf
pure module subroutine stdlib${ii}$_dlagtf( n, a, lambda, b, c, tol, d, in, info )
!! DLAGTF factorizes the matrix (T - lambda*I), where T is an n by n
!! tridiagonal matrix and lambda is a scalar, as
!! T - lambda*I = PLU,
!! where P is a permutation matrix, L is a unit lower tridiagonal matrix
!! with at most one non-zero sub-diagonal elements per column and U is
!! an upper triangular matrix with at most two non-zero super-diagonal
!! elements per column.
!! The factorization is obtained by Gaussian elimination with partial
!! pivoting and implicit row scaling.
!! The parameter LAMBDA is included in the routine so that DLAGTF may
!! be used, in conjunction with DLAGTS, to obtain eigenvectors of T by
!! inverse iteration.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
real(dp), intent(in) :: lambda, tol
! Array Arguments
integer(${ik}$), intent(out) :: in(*)
real(dp), intent(inout) :: a(*), b(*), c(*)
real(dp), intent(out) :: d(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(dp) :: eps, mult, piv1, piv2, scale1, scale2, temp, tl
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( n<0_${ik}$ ) then
info = -1_${ik}$
call stdlib${ii}$_xerbla( 'DLAGTF', -info )
return
end if
if( n==0 )return
a( 1_${ik}$ ) = a( 1_${ik}$ ) - lambda
in( n ) = 0_${ik}$
if( n==1_${ik}$ ) then
if( a( 1_${ik}$ )==zero )in( 1_${ik}$ ) = 1_${ik}$
return
end if
eps = stdlib${ii}$_dlamch( 'EPSILON' )
tl = max( tol, eps )
scale1 = abs( a( 1_${ik}$ ) ) + abs( b( 1_${ik}$ ) )
loop_10: do k = 1, n - 1
a( k+1 ) = a( k+1 ) - lambda
scale2 = abs( c( k ) ) + abs( a( k+1 ) )
if( k<( n-1 ) )scale2 = scale2 + abs( b( k+1 ) )
if( a( k )==zero ) then
piv1 = zero
else
piv1 = abs( a( k ) ) / scale1
end if
if( c( k )==zero ) then
in( k ) = 0_${ik}$
piv2 = zero
scale1 = scale2
if( k<( n-1 ) )d( k ) = zero
else
piv2 = abs( c( k ) ) / scale2
if( piv2<=piv1 ) then
in( k ) = 0_${ik}$
scale1 = scale2
c( k ) = c( k ) / a( k )
a( k+1 ) = a( k+1 ) - c( k )*b( k )
if( k<( n-1 ) )d( k ) = zero
else
in( k ) = 1_${ik}$
mult = a( k ) / c( k )
a( k ) = c( k )
temp = a( k+1 )
a( k+1 ) = b( k ) - mult*temp
if( k<( n-1 ) ) then
d( k ) = b( k+1 )
b( k+1 ) = -mult*d( k )
end if
b( k ) = temp
c( k ) = mult
end if
end if
if( ( max( piv1, piv2 )<=tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = k
end do loop_10
if( ( abs( a( n ) )<=scale1*tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = n
return
end subroutine stdlib${ii}$_dlagtf
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$lagtf( n, a, lambda, b, c, tol, d, in, info )
!! DLAGTF: factorizes the matrix (T - lambda*I), where T is an n by n
!! tridiagonal matrix and lambda is a scalar, as
!! T - lambda*I = PLU,
!! where P is a permutation matrix, L is a unit lower tridiagonal matrix
!! with at most one non-zero sub-diagonal elements per column and U is
!! an upper triangular matrix with at most two non-zero super-diagonal
!! elements per column.
!! The factorization is obtained by Gaussian elimination with partial
!! pivoting and implicit row scaling.
!! The parameter LAMBDA is included in the routine so that DLAGTF may
!! be used, in conjunction with DLAGTS, to obtain eigenvectors of T by
!! inverse iteration.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
real(${rk}$), intent(in) :: lambda, tol
! Array Arguments
integer(${ik}$), intent(out) :: in(*)
real(${rk}$), intent(inout) :: a(*), b(*), c(*)
real(${rk}$), intent(out) :: d(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(${rk}$) :: eps, mult, piv1, piv2, scale1, scale2, temp, tl
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( n<0_${ik}$ ) then
info = -1_${ik}$
call stdlib${ii}$_xerbla( 'DLAGTF', -info )
return
end if
if( n==0 )return
a( 1_${ik}$ ) = a( 1_${ik}$ ) - lambda
in( n ) = 0_${ik}$
if( n==1_${ik}$ ) then
if( a( 1_${ik}$ )==zero )in( 1_${ik}$ ) = 1_${ik}$
return
end if
eps = stdlib${ii}$_${ri}$lamch( 'EPSILON' )
tl = max( tol, eps )
scale1 = abs( a( 1_${ik}$ ) ) + abs( b( 1_${ik}$ ) )
loop_10: do k = 1, n - 1
a( k+1 ) = a( k+1 ) - lambda
scale2 = abs( c( k ) ) + abs( a( k+1 ) )
if( k<( n-1 ) )scale2 = scale2 + abs( b( k+1 ) )
if( a( k )==zero ) then
piv1 = zero
else
piv1 = abs( a( k ) ) / scale1
end if
if( c( k )==zero ) then
in( k ) = 0_${ik}$
piv2 = zero
scale1 = scale2
if( k<( n-1 ) )d( k ) = zero
else
piv2 = abs( c( k ) ) / scale2
if( piv2<=piv1 ) then
in( k ) = 0_${ik}$
scale1 = scale2
c( k ) = c( k ) / a( k )
a( k+1 ) = a( k+1 ) - c( k )*b( k )
if( k<( n-1 ) )d( k ) = zero
else
in( k ) = 1_${ik}$
mult = a( k ) / c( k )
a( k ) = c( k )
temp = a( k+1 )
a( k+1 ) = b( k ) - mult*temp
if( k<( n-1 ) ) then
d( k ) = b( k+1 )
b( k+1 ) = -mult*d( k )
end if
b( k ) = temp
c( k ) = mult
end if
end if
if( ( max( piv1, piv2 )<=tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = k
end do loop_10
if( ( abs( a( n ) )<=scale1*tl ) .and. ( in( n )==0_${ik}$ ) )in( n ) = n
return
end subroutine stdlib${ii}$_${ri}$lagtf
#:endif
#:endfor
pure module subroutine stdlib${ii}$_slagts( job, n, a, b, c, d, in, y, tol, info )
!! SLAGTS may be used to solve one of the systems of equations
!! (T - lambda*I)*x = y or (T - lambda*I)**T*x = y,
!! where T is an n by n tridiagonal matrix, for x, following the
!! factorization of (T - lambda*I) as
!! (T - lambda*I) = P*L*U ,
!! by routine SLAGTF. The choice of equation to be solved is
!! controlled by the argument JOB, and in each case there is an option
!! to perturb zero or very small diagonal elements of U, this option
!! being intended for use in applications such as inverse iteration.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: job, n
real(sp), intent(inout) :: tol
! Array Arguments
integer(${ik}$), intent(in) :: in(*)
real(sp), intent(in) :: a(*), b(*), c(*), d(*)
real(sp), intent(inout) :: y(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(sp) :: absak, ak, bignum, eps, pert, sfmin, temp
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( ( abs( job )>2_${ik}$ ) .or. ( job==0_${ik}$ ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SLAGTS', -info )
return
end if
if( n==0 )return
eps = stdlib${ii}$_slamch( 'EPSILON' )
sfmin = stdlib${ii}$_slamch( 'SAFE MINIMUM' )
bignum = one / sfmin
if( job<0_${ik}$ ) then
if( tol<=zero ) then
tol = abs( a( 1_${ik}$ ) )
if( n>1_${ik}$ )tol = max( tol, abs( a( 2_${ik}$ ) ), abs( b( 1_${ik}$ ) ) )
do k = 3, n
tol = max( tol, abs( a( k ) ), abs( b( k-1 ) ),abs( d( k-2 ) ) )
end do
tol = tol*eps
if( tol==zero )tol = eps
end if
end if
if( abs( job )==1_${ik}$ ) then
do k = 2, n
if( in( k-1 )==0_${ik}$ ) then
y( k ) = y( k ) - c( k-1 )*y( k-1 )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
if( job==1_${ik}$ ) then
loop_30: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_30
else
loop_50: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
40 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
end if
end if
y( k ) = temp / ak
end do loop_50
end if
else
! come to here if job = 2 or -2
if( job==2_${ik}$ ) then
loop_60: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_60
else
loop_80: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
70 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
end if
end if
y( k ) = temp / ak
end do loop_80
end if
do k = n, 2, -1
if( in( k-1 )==0_${ik}$ ) then
y( k-1 ) = y( k-1 ) - c( k-1 )*y( k )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
end if
end subroutine stdlib${ii}$_slagts
pure module subroutine stdlib${ii}$_dlagts( job, n, a, b, c, d, in, y, tol, info )
!! DLAGTS may be used to solve one of the systems of equations
!! (T - lambda*I)*x = y or (T - lambda*I)**T*x = y,
!! where T is an n by n tridiagonal matrix, for x, following the
!! factorization of (T - lambda*I) as
!! (T - lambda*I) = P*L*U ,
!! by routine DLAGTF. The choice of equation to be solved is
!! controlled by the argument JOB, and in each case there is an option
!! to perturb zero or very small diagonal elements of U, this option
!! being intended for use in applications such as inverse iteration.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: job, n
real(dp), intent(inout) :: tol
! Array Arguments
integer(${ik}$), intent(in) :: in(*)
real(dp), intent(in) :: a(*), b(*), c(*), d(*)
real(dp), intent(inout) :: y(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(dp) :: absak, ak, bignum, eps, pert, sfmin, temp
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( ( abs( job )>2_${ik}$ ) .or. ( job==0_${ik}$ ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DLAGTS', -info )
return
end if
if( n==0 )return
eps = stdlib${ii}$_dlamch( 'EPSILON' )
sfmin = stdlib${ii}$_dlamch( 'SAFE MINIMUM' )
bignum = one / sfmin
if( job<0_${ik}$ ) then
if( tol<=zero ) then
tol = abs( a( 1_${ik}$ ) )
if( n>1_${ik}$ )tol = max( tol, abs( a( 2_${ik}$ ) ), abs( b( 1_${ik}$ ) ) )
do k = 3, n
tol = max( tol, abs( a( k ) ), abs( b( k-1 ) ),abs( d( k-2 ) ) )
end do
tol = tol*eps
if( tol==zero )tol = eps
end if
end if
if( abs( job )==1_${ik}$ ) then
do k = 2, n
if( in( k-1 )==0_${ik}$ ) then
y( k ) = y( k ) - c( k-1 )*y( k-1 )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
if( job==1_${ik}$ ) then
loop_30: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_30
else
loop_50: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
40 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
end if
end if
y( k ) = temp / ak
end do loop_50
end if
else
! come to here if job = 2 or -2
if( job==2_${ik}$ ) then
loop_60: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_60
else
loop_80: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
70 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
end if
end if
y( k ) = temp / ak
end do loop_80
end if
do k = n, 2, -1
if( in( k-1 )==0_${ik}$ ) then
y( k-1 ) = y( k-1 ) - c( k-1 )*y( k )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
end if
end subroutine stdlib${ii}$_dlagts
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$lagts( job, n, a, b, c, d, in, y, tol, info )
!! DLAGTS: may be used to solve one of the systems of equations
!! (T - lambda*I)*x = y or (T - lambda*I)**T*x = y,
!! where T is an n by n tridiagonal matrix, for x, following the
!! factorization of (T - lambda*I) as
!! (T - lambda*I) = P*L*U ,
!! by routine DLAGTF. The choice of equation to be solved is
!! controlled by the argument JOB, and in each case there is an option
!! to perturb zero or very small diagonal elements of U, this option
!! being intended for use in applications such as inverse iteration.
! -- lapack auxiliary routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: job, n
real(${rk}$), intent(inout) :: tol
! Array Arguments
integer(${ik}$), intent(in) :: in(*)
real(${rk}$), intent(in) :: a(*), b(*), c(*), d(*)
real(${rk}$), intent(inout) :: y(*)
! =====================================================================
! Local Scalars
integer(${ik}$) :: k
real(${rk}$) :: absak, ak, bignum, eps, pert, sfmin, temp
! Intrinsic Functions
! Executable Statements
info = 0_${ik}$
if( ( abs( job )>2_${ik}$ ) .or. ( job==0_${ik}$ ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DLAGTS', -info )
return
end if
if( n==0 )return
eps = stdlib${ii}$_${ri}$lamch( 'EPSILON' )
sfmin = stdlib${ii}$_${ri}$lamch( 'SAFE MINIMUM' )
bignum = one / sfmin
if( job<0_${ik}$ ) then
if( tol<=zero ) then
tol = abs( a( 1_${ik}$ ) )
if( n>1_${ik}$ )tol = max( tol, abs( a( 2_${ik}$ ) ), abs( b( 1_${ik}$ ) ) )
do k = 3, n
tol = max( tol, abs( a( k ) ), abs( b( k-1 ) ),abs( d( k-2 ) ) )
end do
tol = tol*eps
if( tol==zero )tol = eps
end if
end if
if( abs( job )==1_${ik}$ ) then
do k = 2, n
if( in( k-1 )==0_${ik}$ ) then
y( k ) = y( k ) - c( k-1 )*y( k-1 )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
if( job==1_${ik}$ ) then
loop_30: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_30
else
loop_50: do k = n, 1, -1
if( k<=n-2 ) then
temp = y( k ) - b( k )*y( k+1 ) - d( k )*y( k+2 )
else if( k==n-1 ) then
temp = y( k ) - b( k )*y( k+1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
40 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 40
end if
end if
y( k ) = temp / ak
end do loop_50
end if
else
! come to here if job = 2 or -2
if( job==2_${ik}$ ) then
loop_60: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
info = k
return
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
info = k
return
end if
end if
y( k ) = temp / ak
end do loop_60
else
loop_80: do k = 1, n
if( k>=3_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 ) - d( k-2 )*y( k-2 )
else if( k==2_${ik}$ ) then
temp = y( k ) - b( k-1 )*y( k-1 )
else
temp = y( k )
end if
ak = a( k )
pert = sign( tol, ak )
70 continue
absak = abs( ak )
if( absak<one ) then
if( absak<sfmin ) then
if( absak==zero .or. abs( temp )*sfmin>absak )then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
else
temp = temp*bignum
ak = ak*bignum
end if
else if( abs( temp )>absak*bignum ) then
ak = ak + pert
pert = 2_${ik}$*pert
go to 70
end if
end if
y( k ) = temp / ak
end do loop_80
end if
do k = n, 2, -1
if( in( k-1 )==0_${ik}$ ) then
y( k-1 ) = y( k-1 ) - c( k-1 )*y( k )
else
temp = y( k-1 )
y( k-1 ) = y( k )
y( k ) = temp - c( k-1 )*y( k )
end if
end do
end if
end subroutine stdlib${ii}$_${ri}$lagts
#:endif
#:endfor
pure module subroutine stdlib${ii}$_ssptrd( uplo, n, ap, d, e, tau, info )
!! SSPTRD reduces a real symmetric matrix A stored in packed form to
!! symmetric tridiagonal form T by an orthogonal similarity
!! transformation: Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(sp), intent(inout) :: ap(*)
real(sp), intent(out) :: d(*), e(*), tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
real(sp) :: alpha, taui
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(1:i-1,i+1)
call stdlib${ii}$_slarfg( i, ap( i1+i-1 ), ap( i1 ), 1_${ik}$, taui )
e( i ) = ap( i1+i-1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = one
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_sspmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, zero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_sdot( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_saxpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_sspr2( uplo, i, -one, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
ap( i1+i-1 ) = e( i )
end if
d( i+1 ) = ap( i1+i )
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = ap( 1_${ik}$ )
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(i+2:n,i)
call stdlib${ii}$_slarfg( n-i, ap( ii+1 ), ap( ii+2 ), 1_${ik}$, taui )
e( i ) = ap( ii+1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = one
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_sspmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,zero, tau( i ), &
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_sdot( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_saxpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_sspr2( uplo, n-i, -one, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
ap( ii+1 ) = e( i )
end if
d( i ) = ap( ii )
tau( i ) = taui
ii = i1i1
end do
d( n ) = ap( ii )
end if
return
end subroutine stdlib${ii}$_ssptrd
pure module subroutine stdlib${ii}$_dsptrd( uplo, n, ap, d, e, tau, info )
!! DSPTRD reduces a real symmetric matrix A stored in packed form to
!! symmetric tridiagonal form T by an orthogonal similarity
!! transformation: Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(dp), intent(inout) :: ap(*)
real(dp), intent(out) :: d(*), e(*), tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
real(dp) :: alpha, taui
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(1:i-1,i+1)
call stdlib${ii}$_dlarfg( i, ap( i1+i-1 ), ap( i1 ), 1_${ik}$, taui )
e( i ) = ap( i1+i-1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = one
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_dspmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, zero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_ddot( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_daxpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_dspr2( uplo, i, -one, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
ap( i1+i-1 ) = e( i )
end if
d( i+1 ) = ap( i1+i )
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = ap( 1_${ik}$ )
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(i+2:n,i)
call stdlib${ii}$_dlarfg( n-i, ap( ii+1 ), ap( ii+2 ), 1_${ik}$, taui )
e( i ) = ap( ii+1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = one
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_dspmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,zero, tau( i ), &
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_ddot( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_daxpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_dspr2( uplo, n-i, -one, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
ap( ii+1 ) = e( i )
end if
d( i ) = ap( ii )
tau( i ) = taui
ii = i1i1
end do
d( n ) = ap( ii )
end if
return
end subroutine stdlib${ii}$_dsptrd
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$sptrd( uplo, n, ap, d, e, tau, info )
!! DSPTRD: reduces a real symmetric matrix A stored in packed form to
!! symmetric tridiagonal form T by an orthogonal similarity
!! transformation: Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(${rk}$), intent(inout) :: ap(*)
real(${rk}$), intent(out) :: d(*), e(*), tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
real(${rk}$) :: alpha, taui
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(1:i-1,i+1)
call stdlib${ii}$_${ri}$larfg( i, ap( i1+i-1 ), ap( i1 ), 1_${ik}$, taui )
e( i ) = ap( i1+i-1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = one
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_${ri}$spmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, zero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_${ri}$dot( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_${ri}$axpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_${ri}$spr2( uplo, i, -one, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
ap( i1+i-1 ) = e( i )
end if
d( i+1 ) = ap( i1+i )
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = ap( 1_${ik}$ )
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**t
! to annihilate a(i+2:n,i)
call stdlib${ii}$_${ri}$larfg( n-i, ap( ii+1 ), ap( ii+2 ), 1_${ik}$, taui )
e( i ) = ap( ii+1 )
if( taui/=zero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = one
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_${ri}$spmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,zero, tau( i ), &
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**t *v) * v
alpha = -half*taui*stdlib${ii}$_${ri}$dot( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_${ri}$axpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**t - w * v**t
call stdlib${ii}$_${ri}$spr2( uplo, n-i, -one, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
ap( ii+1 ) = e( i )
end if
d( i ) = ap( ii )
tau( i ) = taui
ii = i1i1
end do
d( n ) = ap( ii )
end if
return
end subroutine stdlib${ii}$_${ri}$sptrd
#:endif
#:endfor
pure module subroutine stdlib${ii}$_sopgtr( uplo, n, ap, tau, q, ldq, work, info )
!! SOPGTR generates a real orthogonal matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! SSPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
real(sp), intent(in) :: ap(*), tau(*)
real(sp), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SOPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_ssptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = zero
end do
do i = 1, n - 1
q( i, n ) = zero
end do
q( n, n ) = one
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_sorg2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_ssptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = one
do i = 2, n
q( i, 1_${ik}$ ) = zero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = zero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_sorg2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_sopgtr
pure module subroutine stdlib${ii}$_dopgtr( uplo, n, ap, tau, q, ldq, work, info )
!! DOPGTR generates a real orthogonal matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! DSPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
real(dp), intent(in) :: ap(*), tau(*)
real(dp), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DOPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_dsptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = zero
end do
do i = 1, n - 1
q( i, n ) = zero
end do
q( n, n ) = one
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_dorg2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_dsptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = one
do i = 2, n
q( i, 1_${ik}$ ) = zero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = zero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_dorg2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_dopgtr
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$opgtr( uplo, n, ap, tau, q, ldq, work, info )
!! DOPGTR: generates a real orthogonal matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! DSPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
real(${rk}$), intent(in) :: ap(*), tau(*)
real(${rk}$), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DOPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_${ri}$sptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = zero
end do
do i = 1, n - 1
q( i, n ) = zero
end do
q( n, n ) = one
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_${ri}$org2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_${ri}$sptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = one
do i = 2, n
q( i, 1_${ik}$ ) = zero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = zero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_${ri}$org2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_${ri}$opgtr
#:endif
#:endfor
pure module subroutine stdlib${ii}$_sopmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! SOPMTR overwrites the general real M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'T': Q**T * C C * Q**T
!! where Q is a real orthogonal matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by SSPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
real(sp), intent(inout) :: ap(*), c(ldc,*)
real(sp), intent(in) :: tau(*)
real(sp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
real(sp) :: aii
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'T' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SOPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_ssptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) is applied to c(1:i,1:n)
mi = i
else
! h(i) is applied to c(1:m,1:i)
ni = i
end if
! apply h(i)
aii = ap( ii )
ap( ii ) = one
call stdlib${ii}$_slarf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, tau( i ), c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_ssptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = one
if( left ) then
! h(i) is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i)
call stdlib${ii}$_slarf( side, mi, ni, ap( ii ), 1_${ik}$, tau( i ),c( ic, jc ), ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do
end if
return
end subroutine stdlib${ii}$_sopmtr
pure module subroutine stdlib${ii}$_dopmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! DOPMTR overwrites the general real M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'T': Q**T * C C * Q**T
!! where Q is a real orthogonal matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by DSPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
real(dp), intent(inout) :: ap(*), c(ldc,*)
real(dp), intent(in) :: tau(*)
real(dp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
real(dp) :: aii
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'T' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DOPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_dsptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) is applied to c(1:i,1:n)
mi = i
else
! h(i) is applied to c(1:m,1:i)
ni = i
end if
! apply h(i)
aii = ap( ii )
ap( ii ) = one
call stdlib${ii}$_dlarf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, tau( i ), c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_dsptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = one
if( left ) then
! h(i) is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i)
call stdlib${ii}$_dlarf( side, mi, ni, ap( ii ), 1_${ik}$, tau( i ),c( ic, jc ), ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do
end if
return
end subroutine stdlib${ii}$_dopmtr
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$opmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! DOPMTR: overwrites the general real M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'T': Q**T * C C * Q**T
!! where Q is a real orthogonal matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by DSPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
real(${rk}$), intent(inout) :: ap(*), c(ldc,*)
real(${rk}$), intent(in) :: tau(*)
real(${rk}$), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
real(${rk}$) :: aii
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'T' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DOPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_${ri}$sptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) is applied to c(1:i,1:n)
mi = i
else
! h(i) is applied to c(1:m,1:i)
ni = i
end if
! apply h(i)
aii = ap( ii )
ap( ii ) = one
call stdlib${ii}$_${ri}$larf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, tau( i ), c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_${ri}$sptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = one
if( left ) then
! h(i) is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i)
call stdlib${ii}$_${ri}$larf( side, mi, ni, ap( ii ), 1_${ik}$, tau( i ),c( ic, jc ), ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do
end if
return
end subroutine stdlib${ii}$_${ri}$opmtr
#:endif
#:endfor
pure module subroutine stdlib${ii}$_ssbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! SSBTRD reduces a real symmetric band matrix A to symmetric
!! tridiagonal form T by an orthogonal similarity transformation:
!! Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(sp), intent(inout) :: ab(ldab,*), q(ldq,*)
real(sp), intent(out) :: d(*), e(*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(sp) :: temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'SSBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_slaset( 'FULL', n, n, zero, one, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the cosines and sines of the plane rotations are stored in the
! arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_slartv or stdlib${ii}$_srot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_slartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_srot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_slartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_srot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_slar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_slartv or stdlib${ii}$_srot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_srot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_srot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_srot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_srot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( kd, i+1 )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( kd1, i )
end do
else
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_slargv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_slartv or stdlib${ii}$_srot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_slartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_srot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_slartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_srot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_slar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_slartv or stdlib${ii}$_srot is used
if( nr>0_${ik}$ ) then
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_slartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_srot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_srot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_srot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_srot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( 2_${ik}$, i )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( 1_${ik}$, i )
end do
end if
return
end subroutine stdlib${ii}$_ssbtrd
pure module subroutine stdlib${ii}$_dsbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! DSBTRD reduces a real symmetric band matrix A to symmetric
!! tridiagonal form T by an orthogonal similarity transformation:
!! Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(dp), intent(inout) :: ab(ldab,*), q(ldq,*)
real(dp), intent(out) :: d(*), e(*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(dp) :: temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_dlaset( 'FULL', n, n, zero, one, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the cosines and sines of the plane rotations are stored in the
! arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_dlartv or stdlib${ii}$_drot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_dlartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_drot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_dlartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_drot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_dlar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_dlartv or stdlib${ii}$_drot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_drot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_drot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_drot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_drot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( kd, i+1 )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( kd1, i )
end do
else
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_dlargv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_dlartv or stdlib${ii}$_drot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_dlartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_drot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_dlartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_drot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_dlar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_dlartv or stdlib${ii}$_drot is used
if( nr>0_${ik}$ ) then
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_dlartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_drot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_drot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_drot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_drot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( 2_${ik}$, i )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( 1_${ik}$, i )
end do
end if
return
end subroutine stdlib${ii}$_dsbtrd
#:for rk,rt,ri in REAL_KINDS_TYPES
#:if not rk in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ri}$sbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! DSBTRD: reduces a real symmetric band matrix A to symmetric
!! tridiagonal form T by an orthogonal similarity transformation:
!! Q**T * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${rk}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(${rk}$), intent(inout) :: ab(ldab,*), q(ldq,*)
real(${rk}$), intent(out) :: d(*), e(*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(${rk}$) :: temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'DSBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_${ri}$laset( 'FULL', n, n, zero, one, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the cosines and sines of the plane rotations are stored in the
! arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_${ri}$lartv or stdlib${ii}$_${ri}$rot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_${ri}$rot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_${ri}$lartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_${ri}$rot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_${ri}$lar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_${ri}$lartv or stdlib${ii}$_${ri}$rot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_${ri}$rot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_${ri}$rot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_${ri}$rot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_${ri}$rot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( kd, i+1 )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( kd1, i )
end do
else
if( kd>1_${ik}$ ) then
! reduce to tridiagonal form, working with lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_${ri}$largv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_${ri}$lartv or stdlib${ii}$_${ri}$rot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_${ri}$lartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_${ri}$rot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_${ri}$lartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_${ri}$rot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_${ri}$lar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_${ri}$lartv or stdlib${ii}$_${ri}$rot is used
if( nr>0_${ik}$ ) then
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_${ri}$lartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_${ri}$rot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_${ri}$rot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_${ri}$rot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_${ri}$rot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! copy off-diagonal elements to e
do i = 1, n - 1
e( i ) = ab( 2_${ik}$, i )
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = ab( 1_${ik}$, i )
end do
end if
return
end subroutine stdlib${ii}$_${ri}$sbtrd
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chptrd( uplo, n, ap, d, e, tau, info )
!! CHPTRD reduces a complex Hermitian matrix A stored in packed form to
!! real symmetric tridiagonal form T by a unitary similarity
!! transformation: Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(sp), intent(out) :: d(*), e(*)
complex(sp), intent(inout) :: ap(*)
complex(sp), intent(out) :: tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
complex(sp) :: alpha, taui
! Intrinsic Functions
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
ap( i1+n-1 ) = real( ap( i1+n-1 ),KIND=sp)
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(1:i-1,i+1)
alpha = ap( i1+i-1 )
call stdlib${ii}$_clarfg( i, alpha, ap( i1 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=sp)
if( taui/=czero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = cone
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_chpmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, czero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_cdotc( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_caxpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_chpr2( uplo, i, -cone, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
end if
ap( i1+i-1 ) = e( i )
d( i+1 ) = real( ap( i1+i ),KIND=sp)
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=sp)
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
ap( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=sp)
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(i+2:n,i)
alpha = ap( ii+1 )
call stdlib${ii}$_clarfg( n-i, alpha, ap( ii+2 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=sp)
if( taui/=czero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = cone
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_chpmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,czero, tau( i ),&
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_cdotc( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_caxpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_chpr2( uplo, n-i, -cone, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
end if
ap( ii+1 ) = e( i )
d( i ) = real( ap( ii ),KIND=sp)
tau( i ) = taui
ii = i1i1
end do
d( n ) = real( ap( ii ),KIND=sp)
end if
return
end subroutine stdlib${ii}$_chptrd
pure module subroutine stdlib${ii}$_zhptrd( uplo, n, ap, d, e, tau, info )
!! ZHPTRD reduces a complex Hermitian matrix A stored in packed form to
!! real symmetric tridiagonal form T by a unitary similarity
!! transformation: Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(dp), intent(out) :: d(*), e(*)
complex(dp), intent(inout) :: ap(*)
complex(dp), intent(out) :: tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
complex(dp) :: alpha, taui
! Intrinsic Functions
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
ap( i1+n-1 ) = real( ap( i1+n-1 ),KIND=dp)
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(1:i-1,i+1)
alpha = ap( i1+i-1 )
call stdlib${ii}$_zlarfg( i, alpha, ap( i1 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=dp)
if( taui/=czero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = cone
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_zhpmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, czero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_zdotc( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_zaxpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_zhpr2( uplo, i, -cone, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
end if
ap( i1+i-1 ) = e( i )
d( i+1 ) = real( ap( i1+i ),KIND=dp)
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=dp)
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
ap( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=dp)
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(i+2:n,i)
alpha = ap( ii+1 )
call stdlib${ii}$_zlarfg( n-i, alpha, ap( ii+2 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=dp)
if( taui/=czero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = cone
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_zhpmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,czero, tau( i ),&
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_zdotc( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_zaxpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_zhpr2( uplo, n-i, -cone, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
end if
ap( ii+1 ) = e( i )
d( i ) = real( ap( ii ),KIND=dp)
tau( i ) = taui
ii = i1i1
end do
d( n ) = real( ap( ii ),KIND=dp)
end if
return
end subroutine stdlib${ii}$_zhptrd
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hptrd( uplo, n, ap, d, e, tau, info )
!! ZHPTRD: reduces a complex Hermitian matrix A stored in packed form to
!! real symmetric tridiagonal form T by a unitary similarity
!! transformation: Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: n
! Array Arguments
real(${ck}$), intent(out) :: d(*), e(*)
complex(${ck}$), intent(inout) :: ap(*)
complex(${ck}$), intent(out) :: tau(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, i1, i1i1, ii
complex(${ck}$) :: alpha, taui
! Intrinsic Functions
! Executable Statements
! test the input parameters
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHPTRD', -info )
return
end if
! quick return if possible
if( n<=0 )return
if( upper ) then
! reduce the upper triangle of a.
! i1 is the index in ap of a(1,i+1).
i1 = n*( n-1 ) / 2_${ik}$ + 1_${ik}$
ap( i1+n-1 ) = real( ap( i1+n-1 ),KIND=${ck}$)
do i = n - 1, 1, -1
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(1:i-1,i+1)
alpha = ap( i1+i-1 )
call stdlib${ii}$_${ci}$larfg( i, alpha, ap( i1 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=${ck}$)
if( taui/=czero ) then
! apply h(i) from both sides to a(1:i,1:i)
ap( i1+i-1 ) = cone
! compute y := tau * a * v storing y in tau(1:i)
call stdlib${ii}$_${ci}$hpmv( uplo, i, taui, ap, ap( i1 ), 1_${ik}$, czero, tau,1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_${ci}$dotc( i, tau, 1_${ik}$, ap( i1 ), 1_${ik}$ )
call stdlib${ii}$_${ci}$axpy( i, alpha, ap( i1 ), 1_${ik}$, tau, 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_${ci}$hpr2( uplo, i, -cone, ap( i1 ), 1_${ik}$, tau, 1_${ik}$, ap )
end if
ap( i1+i-1 ) = e( i )
d( i+1 ) = real( ap( i1+i ),KIND=${ck}$)
tau( i ) = taui
i1 = i1 - i
end do
d( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=${ck}$)
else
! reduce the lower triangle of a. ii is the index in ap of
! a(i,i) and i1i1 is the index of a(i+1,i+1).
ii = 1_${ik}$
ap( 1_${ik}$ ) = real( ap( 1_${ik}$ ),KIND=${ck}$)
do i = 1, n - 1
i1i1 = ii + n - i + 1_${ik}$
! generate elementary reflector h(i) = i - tau * v * v**h
! to annihilate a(i+2:n,i)
alpha = ap( ii+1 )
call stdlib${ii}$_${ci}$larfg( n-i, alpha, ap( ii+2 ), 1_${ik}$, taui )
e( i ) = real( alpha,KIND=${ck}$)
if( taui/=czero ) then
! apply h(i) from both sides to a(i+1:n,i+1:n)
ap( ii+1 ) = cone
! compute y := tau * a * v storing y in tau(i:n-1)
call stdlib${ii}$_${ci}$hpmv( uplo, n-i, taui, ap( i1i1 ), ap( ii+1 ), 1_${ik}$,czero, tau( i ),&
1_${ik}$ )
! compute w := y - 1/2 * tau * (y**h *v) * v
alpha = -chalf*taui*stdlib${ii}$_${ci}$dotc( n-i, tau( i ), 1_${ik}$, ap( ii+1 ),1_${ik}$ )
call stdlib${ii}$_${ci}$axpy( n-i, alpha, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$ )
! apply the transformation as a rank-2 update:
! a := a - v * w**h - w * v**h
call stdlib${ii}$_${ci}$hpr2( uplo, n-i, -cone, ap( ii+1 ), 1_${ik}$, tau( i ), 1_${ik}$,ap( i1i1 ) )
end if
ap( ii+1 ) = e( i )
d( i ) = real( ap( ii ),KIND=${ck}$)
tau( i ) = taui
ii = i1i1
end do
d( n ) = real( ap( ii ),KIND=${ck}$)
end if
return
end subroutine stdlib${ii}$_${ci}$hptrd
#:endif
#:endfor
pure module subroutine stdlib${ii}$_cupgtr( uplo, n, ap, tau, q, ldq, work, info )
!! CUPGTR generates a complex unitary matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! CHPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
complex(sp), intent(in) :: ap(*), tau(*)
complex(sp), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CUPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_chptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = czero
end do
do i = 1, n - 1
q( i, n ) = czero
end do
q( n, n ) = cone
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_cung2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_chptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = cone
do i = 2, n
q( i, 1_${ik}$ ) = czero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = czero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_cung2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_cupgtr
pure module subroutine stdlib${ii}$_zupgtr( uplo, n, ap, tau, q, ldq, work, info )
!! ZUPGTR generates a complex unitary matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! ZHPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
complex(dp), intent(in) :: ap(*), tau(*)
complex(dp), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZUPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_zhptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = czero
end do
do i = 1, n - 1
q( i, n ) = czero
end do
q( n, n ) = cone
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_zung2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_zhptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = cone
do i = 2, n
q( i, 1_${ik}$ ) = czero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = czero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_zung2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_zupgtr
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$upgtr( uplo, n, ap, tau, q, ldq, work, info )
!! ZUPGTR: generates a complex unitary matrix Q which is defined as the
!! product of n-1 elementary reflectors H(i) of order n, as returned by
!! ZHPTRD using packed storage:
!! if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
!! if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldq, n
! Array Arguments
complex(${ck}$), intent(in) :: ap(*), tau(*)
complex(${ck}$), intent(out) :: q(ldq,*), work(*)
! =====================================================================
! Local Scalars
logical(lk) :: upper
integer(${ik}$) :: i, iinfo, ij, j
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
upper = stdlib_lsame( uplo, 'U' )
if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -1_${ik}$
else if( n<0_${ik}$ ) then
info = -2_${ik}$
else if( ldq<max( 1_${ik}$, n ) ) then
info = -6_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZUPGTR', -info )
return
end if
! quick return if possible
if( n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_${ci}$hptrd with uplo = 'u'
! unpack the vectors which define the elementary reflectors and
! set the last row and column of q equal to those of the unit
! matrix
ij = 2_${ik}$
do j = 1, n - 1
do i = 1, j - 1
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
q( n, j ) = czero
end do
do i = 1, n - 1
q( i, n ) = czero
end do
q( n, n ) = cone
! generate q(1:n-1,1:n-1)
call stdlib${ii}$_${ci}$ung2l( n-1, n-1, n-1, q, ldq, tau, work, iinfo )
else
! q was determined by a call to stdlib${ii}$_${ci}$hptrd with uplo = 'l'.
! unpack the vectors which define the elementary reflectors and
! set the first row and column of q equal to those of the unit
! matrix
q( 1_${ik}$, 1_${ik}$ ) = cone
do i = 2, n
q( i, 1_${ik}$ ) = czero
end do
ij = 3_${ik}$
do j = 2, n
q( 1_${ik}$, j ) = czero
do i = j + 1, n
q( i, j ) = ap( ij )
ij = ij + 1_${ik}$
end do
ij = ij + 2_${ik}$
end do
if( n>1_${ik}$ ) then
! generate q(2:n,2:n)
call stdlib${ii}$_${ci}$ung2r( n-1, n-1, n-1, q( 2_${ik}$, 2_${ik}$ ), ldq, tau, work,iinfo )
end if
end if
return
end subroutine stdlib${ii}$_${ci}$upgtr
#:endif
#:endfor
pure module subroutine stdlib${ii}$_cupmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! CUPMTR overwrites the general complex M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'C': Q**H * C C * Q**H
!! where Q is a complex unitary matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by CHPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
complex(sp), intent(inout) :: ap(*), c(ldc,*)
complex(sp), intent(in) :: tau(*)
complex(sp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
complex(sp) :: aii, taui
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'C' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CUPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_chptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) or h(i)**h is applied to c(1:i,1:n)
mi = i
else
! h(i) or h(i)**h is applied to c(1:m,1:i)
ni = i
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
aii = ap( ii )
ap( ii ) = cone
call stdlib${ii}$_clarf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, taui, c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_chptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
loop_20: do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = cone
if( left ) then
! h(i) or h(i)**h is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) or h(i)**h is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
call stdlib${ii}$_clarf( side, mi, ni, ap( ii ), 1_${ik}$, taui, c( ic, jc ),ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_cupmtr
pure module subroutine stdlib${ii}$_zupmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! ZUPMTR overwrites the general complex M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'C': Q**H * C C * Q**H
!! where Q is a complex unitary matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by ZHPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
complex(dp), intent(inout) :: ap(*), c(ldc,*)
complex(dp), intent(in) :: tau(*)
complex(dp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
complex(dp) :: aii, taui
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'C' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZUPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_zhptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) or h(i)**h is applied to c(1:i,1:n)
mi = i
else
! h(i) or h(i)**h is applied to c(1:m,1:i)
ni = i
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
aii = ap( ii )
ap( ii ) = cone
call stdlib${ii}$_zlarf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, taui, c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_zhptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
loop_20: do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = cone
if( left ) then
! h(i) or h(i)**h is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) or h(i)**h is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
call stdlib${ii}$_zlarf( side, mi, ni, ap( ii ), 1_${ik}$, taui, c( ic, jc ),ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_zupmtr
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$upmtr( side, uplo, trans, m, n, ap, tau, c, ldc, work,info )
!! ZUPMTR: overwrites the general complex M-by-N matrix C with
!! SIDE = 'L' SIDE = 'R'
!! TRANS = 'N': Q * C C * Q
!! TRANS = 'C': Q**H * C C * Q**H
!! where Q is a complex unitary matrix of order nq, with nq = m if
!! SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of
!! nq-1 elementary reflectors, as returned by ZHPTRD using packed
!! storage:
!! if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
!! if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: side, trans, uplo
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: ldc, m, n
! Array Arguments
complex(${ck}$), intent(inout) :: ap(*), c(ldc,*)
complex(${ck}$), intent(in) :: tau(*)
complex(${ck}$), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: forwrd, left, notran, upper
integer(${ik}$) :: i, i1, i2, i3, ic, ii, jc, mi, ni, nq
complex(${ck}$) :: aii, taui
! Intrinsic Functions
! Executable Statements
! test the input arguments
info = 0_${ik}$
left = stdlib_lsame( side, 'L' )
notran = stdlib_lsame( trans, 'N' )
upper = stdlib_lsame( uplo, 'U' )
! nq is the order of q
if( left ) then
nq = m
else
nq = n
end if
if( .not.left .and. .not.stdlib_lsame( side, 'R' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( .not.notran .and. .not.stdlib_lsame( trans, 'C' ) ) then
info = -3_${ik}$
else if( m<0_${ik}$ ) then
info = -4_${ik}$
else if( n<0_${ik}$ ) then
info = -5_${ik}$
else if( ldc<max( 1_${ik}$, m ) ) then
info = -9_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZUPMTR', -info )
return
end if
! quick return if possible
if( m==0 .or. n==0 )return
if( upper ) then
! q was determined by a call to stdlib${ii}$_${ci}$hptrd with uplo = 'u'
forwrd = ( left .and. notran ) .or.( .not.left .and. .not.notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
else
mi = m
end if
do i = i1, i2, i3
if( left ) then
! h(i) or h(i)**h is applied to c(1:i,1:n)
mi = i
else
! h(i) or h(i)**h is applied to c(1:m,1:i)
ni = i
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
aii = ap( ii )
ap( ii ) = cone
call stdlib${ii}$_${ci}$larf( side, mi, ni, ap( ii-i+1 ), 1_${ik}$, taui, c, ldc,work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + i + 2_${ik}$
else
ii = ii - i - 1_${ik}$
end if
end do
else
! q was determined by a call to stdlib${ii}$_${ci}$hptrd with uplo = 'l'.
forwrd = ( left .and. .not.notran ) .or.( .not.left .and. notran )
if( forwrd ) then
i1 = 1_${ik}$
i2 = nq - 1_${ik}$
i3 = 1_${ik}$
ii = 2_${ik}$
else
i1 = nq - 1_${ik}$
i2 = 1_${ik}$
i3 = -1_${ik}$
ii = nq*( nq+1 ) / 2_${ik}$ - 1_${ik}$
end if
if( left ) then
ni = n
jc = 1_${ik}$
else
mi = m
ic = 1_${ik}$
end if
loop_20: do i = i1, i2, i3
aii = ap( ii )
ap( ii ) = cone
if( left ) then
! h(i) or h(i)**h is applied to c(i+1:m,1:n)
mi = m - i
ic = i + 1_${ik}$
else
! h(i) or h(i)**h is applied to c(1:m,i+1:n)
ni = n - i
jc = i + 1_${ik}$
end if
! apply h(i) or h(i)**h
if( notran ) then
taui = tau( i )
else
taui = conjg( tau( i ) )
end if
call stdlib${ii}$_${ci}$larf( side, mi, ni, ap( ii ), 1_${ik}$, taui, c( ic, jc ),ldc, work )
ap( ii ) = aii
if( forwrd ) then
ii = ii + nq - i + 1_${ik}$
else
ii = ii - nq + i - 2_${ik}$
end if
end do loop_20
end if
return
end subroutine stdlib${ii}$_${ci}$upmtr
#:endif
#:endfor
pure module subroutine stdlib${ii}$_chbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! CHBTRD reduces a complex Hermitian band matrix A to real symmetric
!! tridiagonal form T by a unitary similarity transformation:
!! Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_sp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(sp), intent(out) :: d(*), e(*)
complex(sp), intent(inout) :: ab(ldab,*), q(ldq,*)
complex(sp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(sp) :: abst
complex(sp) :: t, temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'CHBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_claset( 'FULL', n, n, czero, cone, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the real cosines and complex sines of the plane rotations are
! stored in the arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( kd1, 1_${ik}$ ) = real( ab( kd1, 1_${ik}$ ),KIND=sp)
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_clartv or stdlib${ii}$_crot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_clartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_crot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_clartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_crot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_clar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
call stdlib${ii}$_clacgv( nr, work( j1 ), kd1 )
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_clartv or stdlib${ii}$_crot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_crot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_crot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_crot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
conjg( work( j ) ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_crot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), conjg( &
work( j ) ) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( kd, i+1 )
abst = abs( t )
ab( kd, i+1 ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( kd, i+2 ) = ab( kd, i+2 )*t
if( wantq ) then
call stdlib${ii}$_cscal( n, conjg( t ), q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( kd1, i ),KIND=sp)
end do
else
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( 1_${ik}$, 1_${ik}$ ) = real( ab( 1_${ik}$, 1_${ik}$ ),KIND=sp)
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_clargv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_clartv or stdlib${ii}$_crot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_clartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_crot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_clartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_crot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_clar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_clartv or stdlib${ii}$_crot is used
if( nr>0_${ik}$ ) then
call stdlib${ii}$_clacgv( nr, work( j1 ), kd1 )
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_clartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_crot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_crot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_crot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_crot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( 2_${ik}$, i )
abst = abs( t )
ab( 2_${ik}$, i ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( 2_${ik}$, i+1 ) = ab( 2_${ik}$, i+1 )*t
if( wantq ) then
call stdlib${ii}$_cscal( n, t, q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( 1_${ik}$, i ),KIND=sp)
end do
end if
return
end subroutine stdlib${ii}$_chbtrd
pure module subroutine stdlib${ii}$_zhbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! ZHBTRD reduces a complex Hermitian band matrix A to real symmetric
!! tridiagonal form T by a unitary similarity transformation:
!! Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_dp, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(dp), intent(out) :: d(*), e(*)
complex(dp), intent(inout) :: ab(ldab,*), q(ldq,*)
complex(dp), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(dp) :: abst
complex(dp) :: t, temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_zlaset( 'FULL', n, n, czero, cone, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the real cosines and complex sines of the plane rotations are
! stored in the arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( kd1, 1_${ik}$ ) = real( ab( kd1, 1_${ik}$ ),KIND=dp)
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_zlartv or stdlib${ii}$_zrot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_zlartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_zrot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_zlartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_zrot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_zlar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
call stdlib${ii}$_zlacgv( nr, work( j1 ), kd1 )
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_zlartv or stdlib${ii}$_zrot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_zrot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_zrot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_zrot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
conjg( work( j ) ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_zrot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), conjg( &
work( j ) ) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( kd, i+1 )
abst = abs( t )
ab( kd, i+1 ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( kd, i+2 ) = ab( kd, i+2 )*t
if( wantq ) then
call stdlib${ii}$_zscal( n, conjg( t ), q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( kd1, i ),KIND=dp)
end do
else
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( 1_${ik}$, 1_${ik}$ ) = real( ab( 1_${ik}$, 1_${ik}$ ),KIND=dp)
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_zlargv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_zlartv or stdlib${ii}$_zrot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_zlartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_zrot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_zlartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_zrot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_zlar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_zlartv or stdlib${ii}$_zrot is used
if( nr>0_${ik}$ ) then
call stdlib${ii}$_zlacgv( nr, work( j1 ), kd1 )
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_zlartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_zrot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_zrot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_zrot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_zrot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( 2_${ik}$, i )
abst = abs( t )
ab( 2_${ik}$, i ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( 2_${ik}$, i+1 ) = ab( 2_${ik}$, i+1 )*t
if( wantq ) then
call stdlib${ii}$_zscal( n, t, q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( 1_${ik}$, i ),KIND=dp)
end do
end if
return
end subroutine stdlib${ii}$_zhbtrd
#:for ck,ct,ci in CMPLX_KINDS_TYPES
#:if not ck in ["sp","dp"]
pure module subroutine stdlib${ii}$_${ci}$hbtrd( vect, uplo, n, kd, ab, ldab, d, e, q, ldq,work, info )
!! ZHBTRD: reduces a complex Hermitian band matrix A to real symmetric
!! tridiagonal form T by a unitary similarity transformation:
!! Q**H * A * Q = T.
! -- lapack computational routine --
! -- lapack is a software package provided by univ. of tennessee, --
! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
use stdlib_blas_constants_${ck}$, only: negone, zero, half, one, two, three, four, eight, ten, czero, chalf, cone, cnegone
! Scalar Arguments
character, intent(in) :: uplo, vect
integer(${ik}$), intent(out) :: info
integer(${ik}$), intent(in) :: kd, ldab, ldq, n
! Array Arguments
real(${ck}$), intent(out) :: d(*), e(*)
complex(${ck}$), intent(inout) :: ab(ldab,*), q(ldq,*)
complex(${ck}$), intent(out) :: work(*)
! =====================================================================
! Local Scalars
logical(lk) :: initq, upper, wantq
integer(${ik}$) :: i, i2, ibl, inca, incx, iqaend, iqb, iqend, j, j1, j1end, j1inc, j2, &
jend, jin, jinc, k, kd1, kdm1, kdn, l, last, lend, nq, nr, nrt
real(${ck}$) :: abst
complex(${ck}$) :: t, temp
! Intrinsic Functions
! Executable Statements
! test the input parameters
initq = stdlib_lsame( vect, 'V' )
wantq = initq .or. stdlib_lsame( vect, 'U' )
upper = stdlib_lsame( uplo, 'U' )
kd1 = kd + 1_${ik}$
kdm1 = kd - 1_${ik}$
incx = ldab - 1_${ik}$
iqend = 1_${ik}$
info = 0_${ik}$
if( .not.wantq .and. .not.stdlib_lsame( vect, 'N' ) ) then
info = -1_${ik}$
else if( .not.upper .and. .not.stdlib_lsame( uplo, 'L' ) ) then
info = -2_${ik}$
else if( n<0_${ik}$ ) then
info = -3_${ik}$
else if( kd<0_${ik}$ ) then
info = -4_${ik}$
else if( ldab<kd1 ) then
info = -6_${ik}$
else if( ldq<max( 1_${ik}$, n ) .and. wantq ) then
info = -10_${ik}$
end if
if( info/=0_${ik}$ ) then
call stdlib${ii}$_xerbla( 'ZHBTRD', -info )
return
end if
! quick return if possible
if( n==0 )return
! initialize q to the unit matrix, if needed
if( initq )call stdlib${ii}$_${ci}$laset( 'FULL', n, n, czero, cone, q, ldq )
! wherever possible, plane rotations are generated and applied in
! vector operations of length nr over the index set j1:j2:kd1.
! the real cosines and complex sines of the plane rotations are
! stored in the arrays d and work.
inca = kd1*ldab
kdn = min( n-1, kd )
if( upper ) then
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the upper triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( kd1, 1_${ik}$ ) = real( ab( kd1, 1_${ik}$ ),KIND=${ck}$)
loop_90: do i = 1, n - 2
! reduce i-th row of matrix to tridiagonal form
loop_80: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( 1_${ik}$, j1-1 ), inca, work( j1 ),kd1, d( j1 ), &
kd1 )
! apply rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_${ci}$lartv or stdlib${ii}$_${ci}$rot is used
if( nr>=2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( l+1, j1-1 ), inca,ab( l, j1 ), inca, &
d( j1 ),work( j1 ), kd1 )
end do
else
jend = j1 + ( nr-1 )*kd1
do jinc = j1, jend, kd1
call stdlib${ii}$_${ci}$rot( kdm1, ab( 2_${ik}$, jinc-1 ), 1_${ik}$,ab( 1_${ik}$, jinc ), 1_${ik}$, d( &
jinc ),work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i,i+k-1)
! within the band
call stdlib${ii}$_${ci}$lartg( ab( kd-k+3, i+k-2 ),ab( kd-k+2, i+k-1 ), d( i+k-&
1_${ik}$ ),work( i+k-1 ), temp )
ab( kd-k+3, i+k-2 ) = temp
! apply rotation from the right
call stdlib${ii}$_${ci}$rot( k-3, ab( kd-k+4, i+k-2 ), 1_${ik}$,ab( kd-k+3, i+k-1 ), 1_${ik}$,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_${ci}$lar2v( nr, ab( kd1, j1-1 ), ab( kd1, j1 ),ab( kd, &
j1 ), inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the left
if( nr>0_${ik}$ ) then
call stdlib${ii}$_${ci}$lacgv( nr, work( j1 ), kd1 )
if( 2_${ik}$*kd-1<nr ) then
! dependent on the the number of diagonals either
! stdlib${ii}$_${ci}$lartv or stdlib${ii}$_${ci}$rot is used
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( kd-l, j1+l ), inca,ab( kd-&
l+1, j1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do jin = j1, j1end, kd1
call stdlib${ii}$_${ci}$rot( kd-1, ab( kd-1, jin+1 ), incx,ab( kd, jin+1 )&
, incx,d( jin ), work( jin ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_${ci}$rot( lend, ab( kd-1, last+1 ), incx,ab( kd, &
last+1 ), incx, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_${ci}$rot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
conjg( work( j ) ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_${ci}$rot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), conjg( &
work( j ) ) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j-1,j+kd) outside the band
! and store it in work
work( j+kd ) = work( j )*ab( 1_${ik}$, j+kd )
ab( 1_${ik}$, j+kd ) = d( j )*ab( 1_${ik}$, j+kd )
end do
end do loop_80
end do loop_90
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( kd, i+1 )
abst = abs( t )
ab( kd, i+1 ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( kd, i+2 ) = ab( kd, i+2 )*t
if( wantq ) then
call stdlib${ii}$_${ci}$scal( n, conjg( t ), q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( kd1, i ),KIND=${ck}$)
end do
else
if( kd>1_${ik}$ ) then
! reduce to complex hermitian tridiagonal form, working with
! the lower triangle
nr = 0_${ik}$
j1 = kdn + 2_${ik}$
j2 = 1_${ik}$
ab( 1_${ik}$, 1_${ik}$ ) = real( ab( 1_${ik}$, 1_${ik}$ ),KIND=${ck}$)
loop_210: do i = 1, n - 2
! reduce i-th column of matrix to tridiagonal form
loop_200: do k = kdn + 1, 2, -1
j1 = j1 + kdn
j2 = j2 + kdn
if( nr>0_${ik}$ ) then
! generate plane rotations to annihilate nonzero
! elements which have been created outside the band
call stdlib${ii}$_${ci}$largv( nr, ab( kd1, j1-kd1 ), inca,work( j1 ), kd1, d( j1 )&
, kd1 )
! apply plane rotations from one side
! dependent on the the number of diagonals either
! stdlib${ii}$_${ci}$lartv or stdlib${ii}$_${ci}$rot is used
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
call stdlib${ii}$_${ci}$lartv( nr, ab( kd1-l, j1-kd1+l ), inca,ab( kd1-l+1, &
j1-kd1+l ), inca,d( j1 ), work( j1 ), kd1 )
end do
else
jend = j1 + kd1*( nr-1 )
do jinc = j1, jend, kd1
call stdlib${ii}$_${ci}$rot( kdm1, ab( kd, jinc-kd ), incx,ab( kd1, jinc-kd )&
, incx,d( jinc ), work( jinc ) )
end do
end if
end if
if( k>2_${ik}$ ) then
if( k<=n-i+1 ) then
! generate plane rotation to annihilate a(i+k-1,i)
! within the band
call stdlib${ii}$_${ci}$lartg( ab( k-1, i ), ab( k, i ),d( i+k-1 ), work( i+k-1 &
), temp )
ab( k-1, i ) = temp
! apply rotation from the left
call stdlib${ii}$_${ci}$rot( k-3, ab( k-2, i+1 ), ldab-1,ab( k-1, i+1 ), ldab-1,&
d( i+k-1 ),work( i+k-1 ) )
end if
nr = nr + 1_${ik}$
j1 = j1 - kdn - 1_${ik}$
end if
! apply plane rotations from both sides to diagonal
! blocks
if( nr>0_${ik}$ )call stdlib${ii}$_${ci}$lar2v( nr, ab( 1_${ik}$, j1-1 ), ab( 1_${ik}$, j1 ),ab( 2_${ik}$, j1-1 ),&
inca, d( j1 ),work( j1 ), kd1 )
! apply plane rotations from the right
! dependent on the the number of diagonals either
! stdlib${ii}$_${ci}$lartv or stdlib${ii}$_${ci}$rot is used
if( nr>0_${ik}$ ) then
call stdlib${ii}$_${ci}$lacgv( nr, work( j1 ), kd1 )
if( nr>2_${ik}$*kd-1 ) then
do l = 1, kd - 1
if( j2+l>n ) then
nrt = nr - 1_${ik}$
else
nrt = nr
end if
if( nrt>0_${ik}$ )call stdlib${ii}$_${ci}$lartv( nrt, ab( l+2, j1-1 ), inca,ab( l+1,&
j1 ), inca, d( j1 ),work( j1 ), kd1 )
end do
else
j1end = j1 + kd1*( nr-2 )
if( j1end>=j1 ) then
do j1inc = j1, j1end, kd1
call stdlib${ii}$_${ci}$rot( kdm1, ab( 3_${ik}$, j1inc-1 ), 1_${ik}$,ab( 2_${ik}$, j1inc ), 1_${ik}$, &
d( j1inc ),work( j1inc ) )
end do
end if
lend = min( kdm1, n-j2 )
last = j1end + kd1
if( lend>0_${ik}$ )call stdlib${ii}$_${ci}$rot( lend, ab( 3_${ik}$, last-1 ), 1_${ik}$,ab( 2_${ik}$, last ),&
1_${ik}$, d( last ),work( last ) )
end if
end if
if( wantq ) then
! accumulate product of plane rotations in q
if( initq ) then
! take advantage of the fact that q was
! initially the identity matrix
iqend = max( iqend, j2 )
i2 = max( 0_${ik}$, k-3 )
iqaend = 1_${ik}$ + i*kd
if( k==2_${ik}$ )iqaend = iqaend + kd
iqaend = min( iqaend, iqend )
do j = j1, j2, kd1
ibl = i - i2 / kdm1
i2 = i2 + 1_${ik}$
iqb = max( 1_${ik}$, j-ibl )
nq = 1_${ik}$ + iqaend - iqb
iqaend = min( iqaend+kd, iqend )
call stdlib${ii}$_${ci}$rot( nq, q( iqb, j-1 ), 1_${ik}$, q( iqb, j ),1_${ik}$, d( j ), &
work( j ) )
end do
else
do j = j1, j2, kd1
call stdlib${ii}$_${ci}$rot( n, q( 1_${ik}$, j-1 ), 1_${ik}$, q( 1_${ik}$, j ), 1_${ik}$,d( j ), work( j &
) )
end do
end if
end if
if( j2+kdn>n ) then
! adjust j2 to keep within the bounds of the matrix
nr = nr - 1_${ik}$
j2 = j2 - kdn - 1_${ik}$
end if
do j = j1, j2, kd1
! create nonzero element a(j+kd,j-1) outside the
! band and store it in work
work( j+kd ) = work( j )*ab( kd1, j )
ab( kd1, j ) = d( j )*ab( kd1, j )
end do
end do loop_200
end do loop_210
end if
if( kd>0_${ik}$ ) then
! make off-diagonal elements real and copy them to e
do i = 1, n - 1
t = ab( 2_${ik}$, i )
abst = abs( t )
ab( 2_${ik}$, i ) = abst
e( i ) = abst
if( abst/=zero ) then
t = t / abst
else
t = cone
end if
if( i<n-1 )ab( 2_${ik}$, i+1 ) = ab( 2_${ik}$, i+1 )*t
if( wantq ) then
call stdlib${ii}$_${ci}$scal( n, t, q( 1_${ik}$, i+1 ), 1_${ik}$ )
end if
end do
else
! set e to zero if original matrix was diagonal
do i = 1, n - 1
e( i ) = zero
end do
end if
! copy diagonal elements to d
do i = 1, n
d( i ) = real( ab( 1_${ik}$, i ),KIND=${ck}$)
end do
end if
return
end subroutine stdlib${ii}$_${ci}$hbtrd
#:endif
#:endfor
#:endfor
end submodule stdlib_lapack_eigv_sym_comp
