# dgtts2.f - Man Page

## Synopsis

### Functions/Subroutines

subroutine **dgtts2** (ITRANS, **N**, **NRHS**, DL, D, DU, DU2, IPIV, B, **LDB**)**DGTTS2** solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf.

## Function/Subroutine Documentation

### subroutine dgtts2 (integer ITRANS, integer N, integer NRHS, double precision, dimension( * ) DL, double precision, dimension( * ) D, double precision, dimension( * ) DU, double precision, dimension( * ) DU2, integer, dimension( * ) IPIV, double precision, dimension( ldb, * ) B, integer LDB)

**DGTTS2** solves a system of linear equations with a tridiagonal matrix using the LU factorization computed by sgttrf.

**Purpose:**

DGTTS2 solves one of the systems of equations A*X = B or A**T*X = B, with a tridiagonal matrix A using the LU factorization computed by DGTTRF.

**Parameters:***ITRANS*ITRANS is INTEGER Specifies the form of the system of equations. = 0: A * X = B (No transpose) = 1: A**T* X = B (Transpose) = 2: A**T* X = B (Conjugate transpose = Transpose)

*N*N is INTEGER The order of the matrix A.

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

*DL*DL is DOUBLE PRECISION array, dimension (N-1) The (n-1) multipliers that define the matrix L from the LU factorization of A.

*D*D is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

*DU*DU is DOUBLE PRECISION array, dimension (N-1) The (n-1) elements of the first super-diagonal of U.

*DU2*DU2 is DOUBLE PRECISION array, dimension (N-2) The (n-2) elements of the second super-diagonal of U.

*IPIV*IPIV is INTEGER array, dimension (N) The pivot indices; for 1 <= i <= n, row i of the matrix was interchanged with row IPIV(i). IPIV(i) will always be either i or i+1; IPIV(i) = i indicates a row interchange was not required.

*B*B is DOUBLE PRECISION array, dimension (LDB,NRHS) On entry, the matrix of right hand side vectors B. On exit, B is overwritten by the solution vectors X.

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

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 130 of file dgtts2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dgtts2(3) is an alias of dgtts2.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK