PSPTTRF(3)    ScaLAPACK routine of NEC Numeric Library Collection   PSPTTRF(3)



NAME
       PSPTTRF  - compute a Cholesky factorization of an N-by-N real tridiago-
       nal symmetric positive definite distributed matrix A(1:N, JA:JA+N-1)

SYNOPSIS
       SUBROUTINE PSPTTRF( N, D, E, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

           INTEGER         INFO, JA, LAF, LWORK, N

           INTEGER         DESCA( * )

           REAL            AF( * ), D( * ), E( * ), WORK( * )

PURPOSE
       PSPTTRF computes a Cholesky factorization of an N-by-N real 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 PSPTTRS 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.




ScaLAPACK routine               31 October 2017                     PSPTTRF(3)