laqr1 Interface

public interface laqr1

Given a 2-by-2 or 3-by-3 matrix H, LAQR1: sets v to a scalar multiple of the first column of the product () K = (H - s1I)(H - s2I) scaling to avoid overflows and most underflows. This is useful for starting double implicit shift bulges in the QR algorithm.


Subroutines

public pure subroutine claqr1(n, h, ldh, s1, s2, v)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
complex(kind=sp), intent(in) :: h(ldh,*)
integer(kind=ilp), intent(in) :: ldh
complex(kind=sp), intent(in) :: s1
complex(kind=sp), intent(in) :: s2
complex(kind=sp), intent(out) :: v(*)

public pure subroutine dlaqr1(n, h, ldh, sr1, si1, sr2, si2, v)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
real(kind=dp), intent(in) :: h(ldh,*)
integer(kind=ilp), intent(in) :: ldh
real(kind=dp), intent(in) :: sr1
real(kind=dp), intent(in) :: si1
real(kind=dp), intent(in) :: sr2
real(kind=dp), intent(in) :: si2
real(kind=dp), intent(out) :: v(*)

public pure subroutine slaqr1(n, h, ldh, sr1, si1, sr2, si2, v)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
real(kind=sp), intent(in) :: h(ldh,*)
integer(kind=ilp), intent(in) :: ldh
real(kind=sp), intent(in) :: sr1
real(kind=sp), intent(in) :: si1
real(kind=sp), intent(in) :: sr2
real(kind=sp), intent(in) :: si2
real(kind=sp), intent(out) :: v(*)

public pure subroutine zlaqr1(n, h, ldh, s1, s2, v)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
complex(kind=dp), intent(in) :: h(ldh,*)
integer(kind=ilp), intent(in) :: ldh
complex(kind=dp), intent(in) :: s1
complex(kind=dp), intent(in) :: s2
complex(kind=dp), intent(out) :: v(*)

Module Procedures

public interface stdlib_claqr1()

Arguments

None

public interface stdlib_dlaqr1()

Arguments

None

public interface stdlib_slaqr1()

Arguments

None

public interface stdlib_zlaqr1()

Arguments

None