NAME

       PDPTTRF  -  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 PDPTTRF( N, D, E, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

           INTEGER         INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * )

           DOUBLE          PRECISION AF( * ), D( * ), E( * ), WORK( * )

PURPOSE

       PDPTTRF 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 PDPTTRS 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.