ssteqr - compute all eigenvalues and, optionally, eigenvectors of a symmetric tridiagonal matrix using the implicit QL or QR method
SUBROUTINE SSTEQR( COMPZ, N, D, E, Z, LDZ, WORK, INFO) CHARACTER * 1 COMPZ INTEGER N, LDZ, INFO REAL D(*), E(*), Z(LDZ,*), WORK(*)
SUBROUTINE SSTEQR_64( COMPZ, N, D, E, Z, LDZ, WORK, INFO) CHARACTER * 1 COMPZ INTEGER*8 N, LDZ, INFO REAL D(*), E(*), Z(LDZ,*), WORK(*)
SUBROUTINE STEQR( COMPZ, N, D, E, Z, [LDZ], [WORK], [INFO]) CHARACTER(LEN=1) :: COMPZ INTEGER :: N, LDZ, INFO REAL, DIMENSION(:) :: D, E, WORK REAL, DIMENSION(:,:) :: Z
SUBROUTINE STEQR_64( COMPZ, N, D, E, Z, [LDZ], [WORK], [INFO]) CHARACTER(LEN=1) :: COMPZ INTEGER(8) :: N, LDZ, INFO REAL, DIMENSION(:) :: D, E, WORK REAL, DIMENSION(:,:) :: Z
#include <sunperf.h>
void ssteqr(char compz, int n, float *d, float *e, float *z, int ldz, int *info);
void ssteqr_64(char compz, long n, float *d, float *e, float *z, long ldz, long *info);
ssteqr computes all eigenvalues and, optionally, eigenvectors of a symmetric tridiagonal matrix using the implicit QL or QR method. The eigenvectors of a full or band symmetric matrix can also be found if SSYTRD or SSPTRD or SSBTRD has been used to reduce this matrix to tridiagonal form.
= 'N': Compute eigenvalues only.
= 'V': Compute eigenvalues and eigenvectors of the original symmetric matrix. On entry, Z must contain the orthogonal matrix used to reduce the original matrix to tridiagonal form. = 'I': Compute eigenvalues and eigenvectors of the tridiagonal matrix. Z is initialized to the identity matrix.
dimension(max(1,2*N-2))
If COMPZ = 'N', then WORK is not referenced.
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: the algorithm has failed to find all the eigenvalues in a total of 30*N iterations; if INFO = i, then i elements of E have not converged to zero; on exit, D and E contain the elements of a symmetric tridiagonal matrix which is orthogonally similar to the original matrix.