NAME

       PDPBTRF  -  compute  a  Cholesky  factorization  of  an  N-by-N  real  banded symmetric positive definite
       distributed matrix with bandwidth BW

SYNOPSIS

       SUBROUTINE PDPBTRF( UPLO, N, BW, A, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

           CHARACTER       UPLO

           INTEGER         BW, INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * )

           DOUBLE          PRECISION A( * ), AF( * ), WORK( * )

PURPOSE

       PDPBTRF computes  a  Cholesky  factorization  of  an  N-by-N  real  banded  symmetric  positive  definite
       distributed  matrix  with bandwidth BW: 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 PDPBTRS to solve linear systems.

       The factorization has the form

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

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

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

LAPACK version 1.5                                 12 May 1997                                        PDPBTRF(l)