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 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 California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 146 of file dlasyf_aa.f.
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