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

# cgttrs(3lapack)

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

## NAME

CGTTRS - solves one of the systems of equations  A \* X = B, A\*\*T \* X = B, or A\*\*H \* X = B,

## SYNOPSIS

- SUBROUTINE CGTTRS(

  TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )

- CHARACTER

  TRANS

- INTEGER

  INFO, LDB, N, NRHS

- INTEGER

  IPIV( \* )

- COMPLEX

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

## PURPOSE

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

## ARGUMENTS

- TRANS (input) CHARACTER\*1

  Specifies the form of the system of equations. = 'N':  A \* X = B     (No transpose)\
   \= 'T':  A\*\*T \* X = B  (Transpose)\
   \= 'C':  A\*\*H \* X = B  (Conjugate 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) COMPLEX array, dimension (N-1)

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

- D (input) COMPLEX array, dimension (N)

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

- DU (input) COMPLEX array, dimension (N-1)

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

- DU2 (input) COMPLEX 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) COMPLEX 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).

- INFO (output) INTEGER

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