---
name: "dpttrs"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dpttrs/3lapack"
---

# dpttrs(3lapack)

solves a tridiagonal system of the form A \* X = B using the L\*D\*L' factorization of A computed by DPTTRF

## NAME

DPTTRS - solves a tridiagonal system of the form  A \* X = B using the L\*D\*L' factorization of A computed by DPTTRF

## SYNOPSIS

- SUBROUTINE DPTTRS(

  N, NRHS, D, E, B, LDB, INFO )

- INTEGER

  INFO, LDB, N, NRHS

- DOUBLE

  PRECISION B( LDB, \* ), D( \* ), E( \* )

## PURPOSE

DPTTRS solves a tridiagonal system of the form\
    A \* X = B using the L\*D\*L' factorization of A computed by DPTTRF.  D is a diagonal matrix specified in the vector D, L is a unit bidiagonal matrix whose subdiagonal is specified in the vector E, and X and B are N by NRHS matrices.\

## ARGUMENTS

- N (input) INTEGER

  The order of the tridiagonal matrix A.  N \>= 0.

- NRHS (input) INTEGER

  The number of right hand sides, i.e., the number of columns of the matrix B.  NRHS \>= 0.

- D (input) DOUBLE PRECISION array, dimension (N)

  The n diagonal elements of the diagonal matrix D from the L\*D\*L' factorization of A.

- E (input) DOUBLE PRECISION array, dimension (N-1)

  The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L\*D\*L' factorization of A.  E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U'\*D\*U.

- B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)

  On entry, the right hand side vectors B for the system of linear equations. On exit, the solution vectors, X.

- LDB (input) INTEGER

  The leading dimension of the array B.  LDB \>= max(1,N).

- INFO (output) INTEGER

  \= 0: successful exit\
   \< 0: if INFO = -k, the k-th argument had an illegal value