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)

SYNOPSIS

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

           INTEGER         INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * )

           DOUBLE          PRECISION AF( * ), D( * ), DL( * ), DU( * ), WORK( * )

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
       subsequent calls to PDDTTRS 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.