dsytrf_aa.f man page

dsytrf_aa.f

Synopsis

Functions/Subroutines

subroutine dsytrf_aa (UPLO, N, A, LDA, IPIV, WORK, LWORK, INFO)
DSYTRF_AA

Function/Subroutine Documentation

subroutine dsytrf_aa (character UPLO, integer N, double precision, dimension( lda, * ) A, integer LDA, integer, dimension( * ) IPIV, double precision, dimension( * ) WORK, integer LWORK, integer INFO)

DSYTRF_AA  

Purpose:

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

    A = U*T*U**T  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 DOUBLE PRECISION 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 subdiaonals, 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 DOUBLE PRECISION 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.

Date:

November 2017

Definition at line 134 of file dsytrf_aa.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page dsytrf_aa(3) is an alias of dsytrf_aa.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK