Contents
ssygst - reduce a real symmetric-definite generalized eigen-
problem to standard form
SUBROUTINE SSYGST(ITYPE, UPLO, N, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
INTEGER ITYPE, N, LDA, LDB, INFO
REAL A(LDA,*), B(LDB,*)
SUBROUTINE SSYGST_64(ITYPE, UPLO, N, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
INTEGER*8 ITYPE, N, LDA, LDB, INFO
REAL A(LDA,*), B(LDB,*)
F95 INTERFACE
SUBROUTINE SYGST(ITYPE, UPLO, N, A, [LDA], B, [LDB], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: ITYPE, N, LDA, LDB, INFO
REAL, DIMENSION(:,:) :: A, B
SUBROUTINE SYGST_64(ITYPE, UPLO, N, A, [LDA], B, [LDB], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: ITYPE, N, LDA, LDB, INFO
REAL, DIMENSION(:,:) :: A, B
C INTERFACE
#include <sunperf.h>
void ssygst(int itype, char uplo, int n, float *a, int lda,
float *b, int ldb, int *info);
void ssygst_64(long itype, char uplo, long n, float *a, long
lda, float *b, long ldb, long *info);
ssygst reduces a real symmetric-definite generalized eigen-
problem to standard form.
If ITYPE = 1, the problem is A*x = lambda*B*x,
and A is overwritten by inv(U**T)*A*inv(U) or
inv(L)*A*inv(L**T)
If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
B*A*x = lambda*x, and A is overwritten by U*A*U**T or
L**T*A*L.
B must have been previously factorized as U**T*U or L*L**T
by SPOTRF.
ITYPE (input)
= 1: compute inv(U**T)*A*inv(U) or
inv(L)*A*inv(L**T);
= 2 or 3: compute U*A*U**T or L**T*A*L.
UPLO (input)
= 'U': Upper triangle of A is stored and B is
factored as U**T*U; = 'L': Lower triangle of A is
stored and B is factored as L*L**T.
N (input) The order of the matrices A and B. 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,
and the strictly lower triangular part of A is not
referenced. If UPLO = 'L', the leading N-by-N
lower triangular part of A contains the lower tri-
angular part of the matrix A, and the strictly
upper triangular part of A is not referenced.
On exit, if INFO = 0, the transformed matrix,
stored in the same format as A.
LDA (input)
The leading dimension of the array A. LDA >=
max(1,N).
B (input) The triangular factor from the Cholesky factoriza-
tion of B, as returned by SPOTRF.
LDB (input)
The leading dimension of the array B. LDB >=
max(1,N).
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value