.TH PDDTTRF l "12 May 1997" "LAPACK version 1.5" "LAPACK routine (version 1.5)"
.SH NAME
PDDTTRF \- compute a LU factorization of an N-by-N real tridiagonal diagonally dominant-like distributed matrix A(1:N, JA:JA+N-1)
.SH SYNOPSIS
.TP 20
SUBROUTINE PDDTTRF(
N, DL, D, DU, JA, DESCA, AF, LAF, WORK, LWORK,
INFO )
.TP 20
.ti +4
INTEGER
INFO, JA, LAF, LWORK, N
.TP 20
.ti +4
INTEGER
DESCA( * )
.TP 20
.ti +4
DOUBLE
PRECISION AF( * ), D( * ), DL( * ), DU( * ), WORK( * )
.SH PURPOSE
PDDTTRF computes a LU factorization
of an N-by-N real tridiagonal
diagonally dominant-like distributed matrix
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 PDDTTRS 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 tridiagonal upper triangular matrix and L is tridiagonal
lower triangular, and P is a permutation matrix.
.br