dstev(3P) Sun Performance Library dstev(3P)NAMEdstev - compute all eigenvalues and, optionally, eigenvectors of a real
symmetric tridiagonal matrix A
SYNOPSIS
SUBROUTINE DSTEV(JOBZ, N, D, E, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ
INTEGER N, LDZ, INFO
DOUBLE PRECISION D(*), E(*), Z(LDZ,*), WORK(*)
SUBROUTINE DSTEV_64(JOBZ, N, D, E, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ
INTEGER*8 N, LDZ, INFO
DOUBLE PRECISION D(*), E(*), Z(LDZ,*), WORK(*)
F95 INTERFACE
SUBROUTINE STEV(JOBZ, N, D, E, Z, [LDZ], [WORK], [INFO])
CHARACTER(LEN=1) :: JOBZ
INTEGER :: N, LDZ, INFO
REAL(8), DIMENSION(:) :: D, E, WORK
REAL(8), DIMENSION(:,:) :: Z
SUBROUTINE STEV_64(JOBZ, N, D, E, Z, [LDZ], [WORK], [INFO])
CHARACTER(LEN=1) :: JOBZ
INTEGER(8) :: N, LDZ, INFO
REAL(8), DIMENSION(:) :: D, E, WORK
REAL(8), DIMENSION(:,:) :: Z
C INTERFACE
#include <sunperf.h>
void dstev(char jobz, int n, double *d, double *e, double *z, int ldz,
int *info);
void dstev_64(char jobz, long n, double *d, double *e, double *z, long
ldz, long *info);
PURPOSEdstev computes all eigenvalues and, optionally, eigenvectors of a real
symmetric tridiagonal matrix A.
ARGUMENTS
JOBZ (input)
= 'N': Compute eigenvalues only;
= 'V': Compute eigenvalues and eigenvectors.
N (input) The order of the matrix. N >= 0.
D (input/output)
On entry, the n diagonal elements of the tridiagonal matrix
A. On exit, if INFO = 0, the eigenvalues in ascending order.
E (input/output)
On entry, the (n-1) subdiagonal elements of the tridiagonal
matrix A, stored in elements 1 to N-1 of E; E(N) need not be
set, but is used by the routine. On exit, the contents of E
are destroyed.
Z (output)
If JOBZ = 'V', then if INFO = 0, Z contains the orthonormal
eigenvectors of the matrix A, with the i-th column of Z hold‐
ing the eigenvector associated with D(i). If JOBZ = 'N',
then Z is not referenced.
LDZ (input)
The leading dimension of the array Z. LDZ >= 1, and if JOBZ
= 'V', LDZ >= max(1,N).
WORK (workspace) DOUBLE PRECISION array, dimension (max(1,2*N-2))
If JOBZ = 'N', WORK is not referenced.
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the algorithm failed to converge; i off-
diagonal elements of E did not converge to zero.
6 Mar 2009 dstev(3P)
