Contents
ssbev - compute all the eigenvalues and, optionally, eigen-
vectors of a real symmetric band matrix A
SUBROUTINE SSBEV(JOBZ, UPLO, N, KD, A, LDA, W, Z, LDZ, WORK, INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER N, KD, LDA, LDZ, INFO
REAL A(LDA,*), W(*), Z(LDZ,*), WORK(*)
SUBROUTINE SSBEV_64(JOBZ, UPLO, N, KD, A, LDA, W, Z, LDZ, WORK,
INFO)
CHARACTER * 1 JOBZ, UPLO
INTEGER*8 N, KD, LDA, LDZ, INFO
REAL A(LDA,*), W(*), Z(LDZ,*), WORK(*)
F95 INTERFACE
SUBROUTINE SBEV(JOBZ, UPLO, [N], KD, A, [LDA], W, Z, [LDZ], [WORK],
[INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER :: N, KD, LDA, LDZ, INFO
REAL, DIMENSION(:) :: W, WORK
REAL, DIMENSION(:,:) :: A, Z
SUBROUTINE SBEV_64(JOBZ, UPLO, [N], KD, A, [LDA], W, Z, [LDZ],
[WORK], [INFO])
CHARACTER(LEN=1) :: JOBZ, UPLO
INTEGER(8) :: N, KD, LDA, LDZ, INFO
REAL, DIMENSION(:) :: W, WORK
REAL, DIMENSION(:,:) :: A, Z
C INTERFACE
#include <sunperf.h>
void ssbev(char jobz, char uplo, int n, int kd, float *a,
int lda, float *w, float *z, int ldz, int *info);
void ssbev_64(char jobz, char uplo, long n, long kd, float
*a, long lda, float *w, float *z, long ldz, long
*info);
ssbev computes all the eigenvalues and, optionally, eigen-
vectors of a real symmetric band 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.
KD (input)
The number of superdiagonals of the matrix A if
UPLO = 'U', or the number of subdiagonals if UPLO
= 'L'. KD >= 0.
A (input/output)
On entry, the upper or lower triangle of the sym-
metric band matrix A, stored in the first KD+1
rows of the array. The j-th column of A is stored
in the j-th column of the array A as follows: if
UPLO = 'U', A(kd+1+i-j,j) = A(i,j) for max(1,j-
kd)<=i<=j; if UPLO = 'L', A(1+i-j,j) = A(i,j)
for j<=i<=min(n,j+kd).
On exit, A is overwritten by values generated dur-
ing the reduction to tridiagonal form. If UPLO =
'U', the first superdiagonal and the diagonal of
the tridiagonal matrix T are returned in rows KD
and KD+1 of A, and if UPLO = 'L', the diagonal and
first subdiagonal of T are returned in the first
two rows of A.
LDA (input)
The leading dimension of the array A. LDA >= KD +
1.
W (output)
If INFO = 0, the eigenvalues in ascending order.
Z (input) If JOBZ = 'V', then if INFO = 0, Z contains the
orthonormal eigenvectors of the matrix A, with the
i-th column of Z holding the eigenvector associ-
ated 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)
dimension(MAX(1,3*N-2))
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.