SRC/ssygs2.f(3)            Library Functions Manual            SRC/ssygs2.f(3)

NAME
       SRC/ssygs2.f

SYNOPSIS
   Functions/Subroutines
       subroutine ssygs2 (itype, uplo, n, a, lda, b, ldb, info)
           SSYGS2 reduces a symmetric definite generalized eigenproblem to
           standard form, using the factorization results obtained from spotrf
           (unblocked algorithm).

Function/Subroutine Documentation
   subroutine ssygs2 (integer itype, character uplo, integer n, real,
       dimension( lda, * ) a, integer lda, real, dimension( ldb, * ) b,
       integer ldb, integer info)
       SSYGS2 reduces a symmetric definite generalized eigenproblem to
       standard form, using the factorization results obtained from spotrf
       (unblocked algorithm).

       Purpose:


            SSYGS2 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.

       Parameters
           ITYPE

                     ITYPE is INTEGER
                     = 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

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     symmetric matrix A is stored, and how B has been factorized.
                     = 'U':  Upper triangular
                     = 'L':  Lower triangular

           N

                     N is INTEGER
                     The order of the matrices A and B.  N >= 0.

           A

                     A is REAL array, dimension (LDA,N)
                     On entry, the symmetric matrix A.  If UPLO = 'U', the leading
                     n by n upper triangular part of A contains 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
                     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

                     LDA is INTEGER
                     The leading dimension of the array A.  LDA >= max(1,N).

           B

                     B is REAL array, dimension (LDB,N)
                     The triangular factor from the Cholesky factorization of B,
                     as returned by SPOTRF.

           LDB

                     LDB is INTEGER
                     The leading dimension of the array B.  LDB >= max(1,N).

           INFO

                     INFO is INTEGER
                     = 0:  successful exit.
                     < 0:  if INFO = -i, the i-th argument had an illegal value.

       Author
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Definition at line 126 of file ssygs2.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/ssygs2.f(3)