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.