---
name: "dgtts2"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/dgtts2/3lapack"
---

# dgtts2(3lapack)

solves one of the systems of equations A\*X = B or A'\*X = B,

## NAME

DGTTS2 - solves one of the systems of equations  A\*X = B or A'\*X = B,

## SYNOPSIS

- SUBROUTINE DGTTS2(

  ITRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB )

- INTEGER

  ITRANS, LDB, N, NRHS

- INTEGER

  IPIV( \* )

- DOUBLE

  PRECISION B( LDB, \* ), D( \* ), DL( \* ), DU( \* ), DU2( \* )

## PURPOSE

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

## ARGUMENTS

- ITRANS (input) INTEGER

  Specifies the form of the system of equations. = 0:  A \* X = B  (No transpose)\
   \= 1:  A'\* X = B  (Transpose)\
   \= 2:  A'\* X = B  (Conjugate transpose = Transpose)

- N (input) INTEGER

  The order of the matrix A.

- NRHS (input) INTEGER

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

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

  The (n-1) multipliers that define the matrix L from the LU factorization of A.

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

  The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

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

  The (n-1) elements of the first super-diagonal of U.

- DU2 (input) DOUBLE PRECISION array, dimension (N-2)

  The (n-2) elements of the second super-diagonal of U.

- IPIV (input) 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 (input/output) 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 (input) INTEGER

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