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NAME

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

SYNOPSIS

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

           CHARACTER       UPLO

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

           INTEGER         DESCA( * )

           REAL            A( * ), AF( * ), WORK( * )

PURPOSE

       PSPBTRF  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 PSPBTRS 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.