NAME

       PSPTTRF  -  compute  a  Cholesky  factorization  of  an  N-by-N real tridiagonal symmetric
       positive definite distributed matrix A(1:N, JA:JA+N-1)

SYNOPSIS

       SUBROUTINE PSPTTRF( N, D, E, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

           INTEGER         INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * )

           REAL            AF( * ), D( * ), E( * ), WORK( * )

PURPOSE

       PSPTTRF computes a Cholesky factorization of an N-by-N real tridiagonal symmetric positive
       definite 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 PSPTTRS to solve linear systems.

       The factorization has the form

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

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

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