NAME
PCPTTRF - compute a Cholesky factorization of an N-by-N complex
tridiagonal symmetric positive definite distributed matrix A(1:N,
JA:JA+N-1)
SYNOPSIS
SUBROUTINE PCPTTRF( N, D, E, JA, DESCA, AF, LAF, WORK, LWORK, INFO )
INTEGER INFO, JA, LAF, LWORK, N
INTEGER DESCA( * )
COMPLEX AF( * ), E( * ), WORK( * )
REAL D( * )
PURPOSE
PCPTTRF computes a Cholesky factorization of an N-by-N complex
tridiagonal symmetric positive definite distributed matrix 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 PCPTTRS to solve linear systems.
The factorization has the form
P A(1:N, JA:JA+N-1) P^T = U’ D U or
P A(1:N, JA:JA+N-1) P^T = L D L’,
where U is a tridiagonal upper triangular matrix and L is tridiagonal
lower triangular, and P is a permutation matrix.