ssygst(3P) Sun Performance Library ssygst(3P)NAMEssygst - reduce a real symmetric-definite generalized eigenproblem to
standard form
SYNOPSIS
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);
PURPOSEssygst reduces a real symmetric-definite generalized eigenproblem 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.
ARGUMENTS
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 fac‐
tored 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 contains the upper triangu‐
lar 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 triangular
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 factorization 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 illegal value
6 Mar 2009 ssygst(3P)