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

NAME

PSDTTRF - compute a LU factorization of an N-by-N real tridiagonal diagonally dominant-like distributed matrix A(1:N, JA:JA+N-1)

SYNOPSIS

SUBROUTINE PSDTTRF(

N, DL, D, DU, JA, DESCA, AF, LAF, WORK, LWORK,
INFO )

INTEGER
INFO, JA, LAF, LWORK, N

INTEGER
DESCA( * )

REAL
AF( * ), D( * ), DL( * ), DU( * ), WORK( * )

PURPOSE

PSDTTRF 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
subsequent calls to PSDTTRS to solve linear systems.

The factorization has the form

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

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