PSPBTRF(3)    ScaLAPACK routine of NEC Numeric Library Collection   PSPBTRF(3)



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 sym-
       metric positive definite distributed matrix with bandwidth  BW:  A(1:N,
       JA:JA+N-1).  Reordering  is used to increase parallelism in the factor-
       ization.  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  tri-
       angular, and P is a permutation matrix.




ScaLAPACK routine               31 October 2017                     PSPBTRF(3)