NAME

       PDGBTRF  -  compute  a  LU  factorization of an N-by-N real banded distributed matrix with
       bandwidth BWL, BWU

SYNOPSIS

       SUBROUTINE PDGBTRF( N, BWL, BWU, A, JA, DESCA, IPIV, AF, LAF, WORK, LWORK, INFO )

           INTEGER         BWL, BWU, INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * ), IPIV( * )

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

PURPOSE

       PDGBTRF computes a LU factorization of an  N-by-N  real  banded  distributed  matrix  with
       bandwidth  BWL, BWU: 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 PDGBTRS to solve linear systems.

       The factorization has the form

               P A(1:N, JA:JA+N-1) Q = L U

       where U is a banded upper triangular matrix and L is banded lower triangular, and P and  Q
       are permutation matrices.
       The matrix Q represents reordering of columns
       for parallelism's sake, while P represents
       reordering of rows for numerical stability using
       classic partial pivoting.