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sterf(3) LAPACK sterf(3)

NAME

sterf - sterf: eig, QR iteration

SYNOPSIS

Functions


subroutine dsterf (n, d, e, info)
DSTERF subroutine ssterf (n, d, e, info)
SSTERF

Detailed Description

Function Documentation

subroutine dsterf (integer n, double precision, dimension( * ) d, double precision, dimension( * ) e, integer info)

DSTERF

Purpose:

!>
!> DSTERF computes all eigenvalues of a symmetric tridiagonal matrix
!> using the Pal-Walker-Kahan variant of the QL or QR algorithm.
!>

Parameters

N 

!>          N is INTEGER
!>          The order of the matrix.  N >= 0.
!>

D

!>          D is DOUBLE PRECISION array, dimension (N)
!>          On entry, the n diagonal elements of the tridiagonal matrix.
!>          On exit, if INFO = 0, the eigenvalues in ascending order.
!>

E

!>          E is DOUBLE PRECISION array, dimension (N-1)
!>          On entry, the (n-1) subdiagonal elements of the tridiagonal
!>          matrix.
!>          On exit, E has been destroyed.
!>

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>          > 0:  the algorithm failed to find all of the eigenvalues in
!>                a total of 30*N iterations; if INFO = i, then i
!>                elements of E have not converged to zero.
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

subroutine ssterf (integer n, real, dimension( * ) d, real, dimension( * ) e, integer info)

SSTERF

Purpose:

!>
!> SSTERF computes all eigenvalues of a symmetric tridiagonal matrix
!> using the Pal-Walker-Kahan variant of the QL or QR algorithm.
!>

Parameters

N 

!>          N is INTEGER
!>          The order of the matrix.  N >= 0.
!>

D

!>          D is REAL array, dimension (N)
!>          On entry, the n diagonal elements of the tridiagonal matrix.
!>          On exit, if INFO = 0, the eigenvalues in ascending order.
!>

E

!>          E is REAL array, dimension (N-1)
!>          On entry, the (n-1) subdiagonal elements of the tridiagonal
!>          matrix.
!>          On exit, E has been destroyed.
!>

INFO

!>          INFO is INTEGER
!>          = 0:  successful exit
!>          < 0:  if INFO = -i, the i-th argument had an illegal value
!>          > 0:  the algorithm failed to find all of the eigenvalues in
!>                a total of 30*N iterations; if INFO = i, then i
!>                elements of E have not converged to zero.
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Author

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Tue Jun 30 2026 04:57:07 Version 3.12.0