Contents
dspev - compute all the eigenvalues and, optionally, eigen-
vectors of a real symmetric matrix A in packed storage
SUBROUTINE DSPEV(JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER N, LDZ, INFO
DOUBLE PRECISION AP(*), W(*), Z(LDZ,*), WORK(*)
SUBROUTINE DSPEV_64(JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER*8 N, LDZ, INFO
DOUBLE PRECISION 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(8), DIMENSION(:) :: AP, W, WORK
REAL(8), 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(8), DIMENSION(:) :: AP, W, WORK
REAL(8), DIMENSION(:,:) :: Z
C INTERFACE
#include <sunperf.h>
void dspev(char jobz, char uplo, int n, double *ap, double
*w, double *z, int ldz, int *info);
void dspev_64(char jobz, char uplo, long n, double *ap, dou-
ble *w, double *z, long ldz, long *info);
dspev 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)
Double precision array, dimension (N*(N+1)/2) On
entry, the upper or lower triangle of the sym-
metric 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)
Double precision array, dimension (N) If INFO = 0,
the eigenvalues in ascending order.
Z (output)
Double precision array, dimension (LDZ, N) If JOBZ
= 'V', then if INFO = 0, Z contains the orthonor-
mal eigenvectors 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 refer-
enced.
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(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.