disna Interface

public interface disna

DISNA 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. DISNA may also be used to compute error bounds for eigenvectors of the generalized symmetric definite eigenproblem.


Subroutines

public pure subroutine ddisna(job, m, n, d, sep, info)

Arguments

Type IntentOptional Attributes Name
character(len=1), intent(in) :: job
integer(kind=ilp), intent(in) :: m
integer(kind=ilp), intent(in) :: n
real(kind=dp), intent(in) :: d(*)
real(kind=dp), intent(out) :: sep(*)
integer(kind=ilp), intent(out) :: info

public pure subroutine sdisna(job, m, n, d, sep, info)

Arguments

Type IntentOptional Attributes Name
character(len=1), intent(in) :: job
integer(kind=ilp), intent(in) :: m
integer(kind=ilp), intent(in) :: n
real(kind=sp), intent(in) :: d(*)
real(kind=sp), intent(out) :: sep(*)
integer(kind=ilp), intent(out) :: info

Module Procedures

public interface stdlib_ddisna()

Arguments

None

public interface stdlib_sdisna()

Arguments

None