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

NAME
       SRC/ssytrf_aa.f

SYNOPSIS
   Functions/Subroutines
       subroutine ssytrf_aa (uplo, n, a, lda, ipiv, work, lwork, info)
           SSYTRF_AA

Function/Subroutine Documentation
   subroutine ssytrf_aa (character uplo, integer n, real, dimension( lda, * )
       a, integer lda, integer, dimension( * ) ipiv, real, dimension( * )
       work, integer lwork, integer info)
       SSYTRF_AA

       Purpose:


            SSYTRF_AA computes the factorization of a real symmetric matrix A
            using the Aasen's algorithm.  The form of the factorization is

               A = U**T*T*U  or  A = L*T*L**T

            where U (or L) is a product of permutation and unit upper (lower)
            triangular matrices, and T is a symmetric tridiagonal matrix.

            This is the blocked version of the algorithm, calling Level 3 BLAS.

       Parameters
           UPLO

                     UPLO is CHARACTER*1
                     = 'U':  Upper triangle of A is stored;
                     = 'L':  Lower triangle of A is stored.

           N

                     N is INTEGER
                     The order of the matrix A.  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, the tridiagonal matrix is stored in the diagonals
                     and the subdiagonals of A just below (or above) the diagonals,
                     and L is stored below (or above) the subdiagonals, when UPLO
                     is 'L' (or 'U').

           LDA

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

           IPIV

                     IPIV is INTEGER array, dimension (N)
                     On exit, it contains the details of the interchanges, i.e.,
                     the row and column k of A were interchanged with the
                     row and column IPIV(k).

           WORK

                     WORK is REAL array, dimension (MAX(1,LWORK))
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The length of WORK.  LWORK >= MAX(1,2*N). For optimum performance
                     LWORK >= N*(1+NB), where NB is the optimal blocksize.

                     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.

           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 131 of file ssytrf_aa.f.

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

LAPACK                          Version 3.12.0              SRC/ssytrf_aa.f(3)