Section: LAPACK routine (version 1.5) (l)Updated: 12 May 1997Local indexUp

NAME

PDPBTRF - compute a Cholesky factorization of an N-by-N real banded symmetric positive definite distributed matrix with bandwidth BW

SYNOPSIS

SUBROUTINE PDPBTRF(

UPLO, N, BW, A, JA, DESCA, AF, LAF, WORK,
LWORK, INFO )

CHARACTER
UPLO

INTEGER
BW, INFO, JA, LAF, LWORK, N

INTEGER
DESCA( * )

DOUBLE
PRECISION A( * ), AF( * ), WORK( * )

PURPOSE

PDPBTRF computes a Cholesky factorization
of an N-by-N real banded
symmetric positive definite distributed matrix
with bandwidth BW: A(1:N, JA:JA+N-1).
Reordering is used to increase parallelism in the factorization.
This reordering results in factors that are DIFFERENT from those
produced by equivalent sequential codes. These factors cannot
be used directly by users; however, they can be used in
subsequent calls to PDPBTRS to solve linear systems.

The factorization has the form

P A(1:N, JA:JA+N-1) P^T = U' U , if UPLO = 'U', or

P A(1:N, JA:JA+N-1) P^T = L L', if UPLO = 'L'

where U is a banded upper triangular matrix and L is banded
lower triangular, and P is a permutation matrix.