pcpttrf(3)
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.