sstevd - compute all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix
SUBROUTINE SSTEVD( JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK, * LIWORK, INFO) CHARACTER * 1 JOBZ INTEGER N, LDZ, LWORK, LIWORK, INFO INTEGER IWORK(*) REAL D(*), E(*), Z(LDZ,*), WORK(*)
SUBROUTINE SSTEVD_64( JOBZ, N, D, E, Z, LDZ, WORK, LWORK, IWORK, * LIWORK, INFO) CHARACTER * 1 JOBZ INTEGER*8 N, LDZ, LWORK, LIWORK, INFO INTEGER*8 IWORK(*) REAL D(*), E(*), Z(LDZ,*), WORK(*)
SUBROUTINE STEVD( JOBZ, [N], D, E, Z, [LDZ], [WORK], [LWORK], [IWORK], * [LIWORK], [INFO]) CHARACTER(LEN=1) :: JOBZ INTEGER :: N, LDZ, LWORK, LIWORK, INFO INTEGER, DIMENSION(:) :: IWORK REAL, DIMENSION(:) :: D, E, WORK REAL, DIMENSION(:,:) :: Z
SUBROUTINE STEVD_64( JOBZ, [N], D, E, Z, [LDZ], [WORK], [LWORK], * [IWORK], [LIWORK], [INFO]) CHARACTER(LEN=1) :: JOBZ INTEGER(8) :: N, LDZ, LWORK, LIWORK, INFO INTEGER(8), DIMENSION(:) :: IWORK REAL, DIMENSION(:) :: D, E, WORK REAL, DIMENSION(:,:) :: Z
#include <sunperf.h>
void sstevd(char jobz, int n, float *d, float *e, float *z, int ldz, int *info);
void sstevd_64(char jobz, long n, float *d, float *e, float *z, long ldz, long *info);
sstevd computes all eigenvalues and, optionally, eigenvectors of a real symmetric tridiagonal matrix. If eigenvectors are desired, it uses a divide and conquer algorithm.
The divide and conquer algorithm makes very mild assumptions about floating point arithmetic. It will work on machines with a guard digit in add/subtract, or on those binary machines without guard digits which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2. It could conceivably fail on hexadecimal or decimal machines without guard digits, but we know of none.
= 'N': Compute eigenvalues only;
= 'V': Compute eigenvalues and eigenvectors.
E(N)
need not
be set, but is used by the routine.
On exit, the contents of E are destroyed.
WORK(1)
returns the optimal LWORK.
If LWORK = -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 LWORK is issued by XERBLA.
IWORK(1)
returns the optimal LIWORK.
If LIWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the IWORK array, returns this value as the first entry of the IWORK array, and no error message related to LIWORK is issued by XERBLA.
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the algorithm failed to converge; i off-diagonal elements of E did not converge to zero.