PDDTTRF - compute a LU factorization of an N-by-N real tridiagonal diagonally
dominant-like distributed matrix A(1:N, JA:JA+N-1)

- SUBROUTINE PDDTTRF(
- N, DL, D, DU, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

INTEGER INFO, JA, LAF, LWORK, N INTEGER DESCA( * ) DOUBLE PRECISION AF( * ), D(
* ), DL( * ), DU( * ), WORK( * )

PDDTTRF computes a LU factorization of an N-by-N real tridiagonal diagonally
dominant-like 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 PDDTTRS to solve linear systems.

The factorization has the form

P A(1:N, JA:JA+N-1) P^T = L U

where U is a tridiagonal upper triangular matrix and L is tridiagonal lower
triangular, and P is a permutation matrix.