Contents
sspev - compute all the eigenvalues and, optionally, eigen-
vectors of a real symmetric matrix A in packed storage
SUBROUTINE SSPEV(JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER N, LDZ, INFO
REAL AP(*), W(*), Z(LDZ,*), WORK(*)
SUBROUTINE SSPEV_64(JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER*8 N, LDZ, INFO
REAL AP(*), W(*), Z(LDZ,*), WORK(*)
F95 INTERFACE
SUBROUTINE SPEV(JOBZ, UPLO, [N], AP, W, Z, [LDZ], [WORK], [INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER :: N, LDZ, INFO
REAL, DIMENSION(:) :: AP, W, WORK
REAL, DIMENSION(:,:) :: Z
SUBROUTINE SPEV_64(JOBZ, UPLO, [N], AP, W, Z, [LDZ], [WORK], [INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER(8) :: N, LDZ, INFO
REAL, DIMENSION(:) :: AP, W, WORK
REAL, DIMENSION(:,:) :: Z
C INTERFACE
#include <sunperf.h>
void sspev(char jobz, char uplo, int n, float *ap, float *w,
float *z, int ldz, int *info);
void sspev_64(char jobz, char uplo, long n, float *ap, float
*w, float *z, long ldz, long *info);
sspev computes all the eigenvalues and, optionally, eigen-
vectors of a real symmetric matrix A in packed storage.
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.
AP (input/output)
Real array, dimension (N*(N+1)/2) On entry, the
upper or lower triangle of the symmetric matrix A,
packed columnwise in a linear array. The j-th
column of A is stored in the array AP as follows:
if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for
1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2) =
A(i,j) for j<=i<=n.
On exit, AP is overwritten by values generated
during the reduction to tridiagonal form. If UPLO
= 'U', the diagonal and first superdiagonal of the
tridiagonal matrix T overwrite the corresponding
elements of A, and if UPLO = 'L', the diagonal and
first subdiagonal of T overwrite the corresponding
elements of A.
W (output)
Real array, dimension (N) If INFO = 0, the eigen-
values in ascending order.
Z (output)
Real array, dimension (LDZ, N) If JOBZ = 'V', then
if INFO = 0, Z contains the orthonormal eigenvec-
tors of the matrix A, with the i-th column of Z
holding the eigenvector associated with W(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)
Real array, dimension(3*N)
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.