• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dsterf - compute all eigenvalues of a symmetric tridiagonal matrix using the Pal-Walker-Kahan variant of the QL or QR algorithm

SYNOPSIS

  SUBROUTINE DSTERF( N, D, E, INFO)
  INTEGER N, INFO
  DOUBLE PRECISION D(*), E(*)

  SUBROUTINE DSTERF_64( N, D, E, INFO)
  INTEGER*8 N, INFO
  DOUBLE PRECISION D(*), E(*)

F95 INTERFACE

  SUBROUTINE STERF( [N], D, E, [INFO])
  INTEGER :: N, INFO
  REAL(8), DIMENSION(:) :: D, E

  SUBROUTINE STERF_64( [N], D, E, [INFO])
  INTEGER(8) :: N, INFO
  REAL(8), DIMENSION(:) :: D, E

C INTERFACE

#include <sunperf.h>

void dsterf(int n, double *d, double *e, int *info);

void dsterf_64(long n, double *d, double *e, long *info);

PURPOSE

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

ARGUMENTS

• N (input)
  The order of the matrix. N > = 0.

• D (input/output)
  On entry, the n diagonal elements of the tridiagonal matrix. On exit, if INFO = 0, the eigenvalues in ascending order.

• E (input/output)
  On entry, the (n-1) subdiagonal elements of the tridiagonal matrix. On exit, E has been destroyed.

• INFO (output)
  

   = 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.