dlasyf_aa.f - Man Page

subroutine dlasyf_aa (uplo, j1, m, nb, a, lda, ipiv, h, ldh, work)
DLASYF_AA

DLASYF_AA  

Purpose:

 DLATRF_AA factorizes a panel of a real symmetric matrix A using
 the Aasen's algorithm. The panel consists of a set of NB rows of A
 when UPLO is U, or a set of NB columns when UPLO is L.

 In order to factorize the panel, the Aasen's algorithm requires the
 last row, or column, of the previous panel. The first row, or column,
 of A is set to be the first row, or column, of an identity matrix,
 which is used to factorize the first panel.

 The resulting J-th row of U, or J-th column of L, is stored in the
 (J-1)-th row, or column, of A (without the unit diagonals), while
 the diagonal and subdiagonal of A are overwritten by those of T.

Parameters

UPLO

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

J1

          J1 is INTEGER
          The location of the first row, or column, of the panel
          within the submatrix of A, passed to this routine, e.g.,
          when called by DSYTRF_AA, for the first panel, J1 is 1,
          while for the remaining panels, J1 is 2.

M

          M is INTEGER
          The dimension of the submatrix. M >= 0.

NB

          NB is INTEGER
          The dimension of the panel to be facotorized.

A

          A is DOUBLE PRECISION array, dimension (LDA,M) for
          the first panel, while dimension (LDA,M+1) for the
          remaining panels.

          On entry, A contains the last row, or column, of
          the previous panel, and the trailing submatrix of A
          to be factorized, except for the first panel, only
          the panel is passed.

          On exit, the leading panel is factorized.

LDA

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

IPIV

          IPIV is INTEGER array, dimension (M)
          Details of the row and column interchanges,
          the row and column k were interchanged with the row and
          column IPIV(k).

H

          H is DOUBLE PRECISION workspace, dimension (LDH,NB).

LDH

          LDH is INTEGER
          The leading dimension of the workspace H. LDH >= max(1,M).

WORK

          WORK is DOUBLE PRECISION workspace, dimension (M).

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 142 of file dlasyf_aa.f.