SRC/chegs2.f(3)            Library Functions Manual            SRC/chegs2.f(3)

NAME
       SRC/chegs2.f

SYNOPSIS
   Functions/Subroutines
       subroutine chegs2 (itype, uplo, n, a, lda, b, ldb, info)
           CHEGS2 reduces a Hermitian definite generalized eigenproblem to
           standard form, using the factorization results obtained from cpotrf
           (unblocked algorithm).

Function/Subroutine Documentation
   subroutine chegs2 (integer itype, character uplo, integer n, complex,
       dimension( lda, * ) a, integer lda, complex, dimension( ldb, * ) b,
       integer ldb, integer info)
       CHEGS2 reduces a Hermitian definite generalized eigenproblem to
       standard form, using the factorization results obtained from cpotrf
       (unblocked algorithm).

       Purpose:


            CHEGS2 reduces a complex Hermitian-definite generalized
            eigenproblem to standard form.

            If ITYPE = 1, the problem is A*x = lambda*B*x,
            and A is overwritten by inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H)

            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**H or L**H *A*L.

            B must have been previously factorized as U**H *U or L*L**H by ZPOTRF.

       Parameters
           ITYPE

                     ITYPE is INTEGER
                     = 1: compute inv(U**H)*A*inv(U) or inv(L)*A*inv(L**H);
                     = 2 or 3: compute U*A*U**H or L**H *A*L.

           UPLO

                     UPLO is CHARACTER*1
                     Specifies whether the upper or lower triangular part of the
                     Hermitian 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 COMPLEX array, dimension (LDA,N)
                     On entry, the Hermitian 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 COMPLEX array, dimension (LDB,N)
                     The triangular factor from the Cholesky factorization of B,
                     as returned by CPOTRF.
                     B is modified by the routine but restored on exit.

           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 127 of file chegs2.f.

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

LAPACK                          Version 3.12.0                 SRC/chegs2.f(3)