.TH PDDBTRF l "12 May 1997" "LAPACK version 1.5" "LAPACK routine (version 1.5)"
.SH NAME
PDDBTRF \- compute a LU factorization of an N-by-N real banded diagonally dominant-like distributed matrix with bandwidth BWL, BWU
.SH SYNOPSIS
.TP 20
SUBROUTINE PDDBTRF(
N, BWL, BWU, A, JA, DESCA, AF, LAF, WORK,
LWORK, INFO )
.TP 20
.ti +4
INTEGER
BWL, BWU, INFO, JA, LAF, LWORK, N
.TP 20
.ti +4
INTEGER
DESCA( * )
.TP 20
.ti +4
DOUBLE
PRECISION A( * ), AF( * ), WORK( * )
.SH PURPOSE
PDDBTRF computes a LU factorization
of an N-by-N real banded
diagonally dominant-like distributed matrix
with bandwidth BWL, BWU: 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
.br
subsequent calls to PDDBTRS to solve linear systems.
.br

The factorization has the form
.br

        P A(1:N, JA:JA+N-1) P^T = L U
.br

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