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.