Contents
ssyev - compute all eigenvalues and, optionally, eigenvec-
tors of a real symmetric matrix A
SUBROUTINE SSYEV(JOBZ, UPLO, N, A, LDA, W, WORK, LDWORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER N, LDA, LDWORK, INFO
REAL A(LDA,*), W(*), WORK(*)
SUBROUTINE SSYEV_64(JOBZ, UPLO, N, A, LDA, W, WORK, LDWORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER*8 N, LDA, LDWORK, INFO
REAL A(LDA,*), W(*), WORK(*)
F95 INTERFACE
SUBROUTINE SYEV(JOBZ, UPLO, N, A, [LDA], W, [WORK], [LDWORK], [INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER :: N, LDA, LDWORK, INFO
REAL, DIMENSION(:) :: W, WORK
REAL, DIMENSION(:,:) :: A
SUBROUTINE SYEV_64(JOBZ, UPLO, N, A, [LDA], W, [WORK], [LDWORK],
[INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER(8) :: N, LDA, LDWORK, INFO
REAL, DIMENSION(:) :: W, WORK
REAL, DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void ssyev(char jobz, char uplo, int n, float *a, int lda,
float *w, int *info);
void ssyev_64(char jobz, char uplo, long n, float *a, long
lda, float *w, long *info);
ssyev computes all eigenvalues and, optionally, eigenvectors
of a real symmetric matrix A.
JOBZ (input)
= 'N': Compute eigenvalues only;
= 'V': Compute eigenvalues and eigenvectors.
UPLO (input)
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) The order of the matrix A. N >= 0.
A (input/output)
On entry, the symmetric matrix A. If UPLO = 'U',
the leading N-by-N upper triangular part of A con-
tains the upper triangular part of the matrix A.
If UPLO = 'L', the leading N-by-N lower triangular
part of A contains the lower triangular part of
the matrix A. On exit, if JOBZ = 'V', then if
INFO = 0, A contains the orthonormal eigenvectors
of the matrix A. If JOBZ = 'N', then on exit the
lower triangle (if UPLO='L') or the upper triangle
(if UPLO='U') of A, including the diagonal, is
destroyed.
LDA (input)
The leading dimension of the array A. LDA >=
max(1,N).
W (output)
If INFO = 0, the eigenvalues in ascending order.
WORK (workspace)
On exit, if INFO = 0, WORK(1) returns the optimal
LDWORK.
LDWORK (input)
The length of the array WORK. LDWORK >=
max(1,3*N-1). For optimal efficiency, LDWORK >=
(NB+2)*N, where NB is the blocksize for SSYTRD
returned by ILAENV.
If LDWORK = -1, then a workspace query is assumed;
the routine only calculates the optimal size of
the WORK array, returns this value as the first
entry of the WORK array, and no error message
related to LDWORK is issued by XERBLA.
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value
> 0: if INFO = i, the algorithm failed to con-
verge; i off-diagonal elements of an intermediate
tridiagonal form did not converge to zero.