larrk Interface

public interface larrk

LARRK computes one eigenvalue of a symmetric tridiagonal matrix T to suitable accuracy. This is an auxiliary code to be called from DSTEMR. To avoid overflow, the matrix must be scaled so that its largest element is no greater than overflow(1/2) * underflow(1/4) in absolute value, and for greatest accuracy, it should not be much smaller than that. See W. Kahan "Accurate Eigenvalues of a Symmetric Tridiagonal Matrix", Report CS41, Computer Science Dept., Stanford University, July 21, 1966.


Subroutines

public pure subroutine dlarrk(n, iw, gl, gu, d, e2, pivmin, reltol, w, werr, info)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
integer(kind=ilp), intent(in) :: iw
real(kind=dp), intent(in) :: gl
real(kind=dp), intent(in) :: gu
real(kind=dp), intent(in) :: d(*)
real(kind=dp), intent(in) :: e2(*)
real(kind=dp), intent(in) :: pivmin
real(kind=dp), intent(in) :: reltol
real(kind=dp), intent(out) :: w
real(kind=dp), intent(out) :: werr
integer(kind=ilp), intent(out) :: info

public pure subroutine slarrk(n, iw, gl, gu, d, e2, pivmin, reltol, w, werr, info)

Arguments

Type IntentOptional Attributes Name
integer(kind=ilp), intent(in) :: n
integer(kind=ilp), intent(in) :: iw
real(kind=sp), intent(in) :: gl
real(kind=sp), intent(in) :: gu
real(kind=sp), intent(in) :: d(*)
real(kind=sp), intent(in) :: e2(*)
real(kind=sp), intent(in) :: pivmin
real(kind=sp), intent(in) :: reltol
real(kind=sp), intent(out) :: w
real(kind=sp), intent(out) :: werr
integer(kind=ilp), intent(out) :: info

Module Procedures

public interface stdlib_dlarrk()

Arguments

None

public interface stdlib_slarrk()

Arguments

None