PCGBTRF(l) LAPACK routine (version 1.5) PCGBTRF(l)
NAME
PCGBTRF - compute a LU factorization of an N-by-N complex banded distributed matrix with bandwidth BWL, BWU
SYNOPSIS
SUBROUTINE PCGBTRF( N, BWL, BWU, A, JA, DESCA, IPIV, AF, LAF, WORK, LWORK, INFO )
INTEGER BWL, BWU, INFO, JA, LAF, LWORK, N
INTEGER DESCA( * ), IPIV( * )
COMPLEX A( * ), AF( * ), WORK( * )
PURPOSE
PCGBTRF computes a LU factorization of an N-by-N complex 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 equiva-
lent sequential codes. These factors cannot be used directly by users; however, they can be used in
subsequent calls to PCGBTRS 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.
LAPACK version 1.5 12 May 1997 PCGBTRF(l)
