---
name: "pddbtrf"
section: "3"
platform: "linux"
package: "scalapack-doc"
version: "1.5-11"
release: "Debian 11 (Bullseye)"
platforms: ["linux"]
url: "https://new.carta.tech/pddbtrf"
---

# pddbtrf(3)

compute a LU factorization of an N-by-N real banded diagonally dominant-like distributed matrix with bandwidth BWL, BWU

## NAME

PDDBTRF - compute a LU factorization of an N-by-N real banded diagonally dominant-like distributed matrix with bandwidth BWL, BWU

## SYNOPSIS

- SUBROUTINE PDDBTRF(

  N, BWL, BWU, A, JA, DESCA, AF, LAF, WORK, LWORK, INFO )

- INTEGER

  BWL, BWU, INFO, JA, LAF, LWORK, N

- INTEGER

  DESCA( \* )

- DOUBLE

  PRECISION A( \* ), AF( \* ), WORK( \* )

## PURPOSE

PDDBTRF computes a LU factorization of an N-by-N real banded diagonally dominant-like 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 equivalent sequential codes. These factors cannot be used directly by users; however, they can be used in\
 subsequent calls to PDDBTRS 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 banded upper triangular matrix and L is banded lower triangular, and P is a permutation matrix.\