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

# zlagtm(3lapack)

performs a matrix-vector product of the form B := alpha \* A \* X + beta \* B where A is a tridiagonal matrix of order N, B and X are N by NRHS matrices, and alpha and beta are real scalars, each of which may be 0., 1., or -1

## NAME

ZLAGTM - performs a matrix-vector product of the form   B := alpha \* A \* X + beta \* B  where A is a tridiagonal matrix of order N, B and X are N by NRHS matrices, and alpha and beta are real scalars, each of which may be 0., 1., or -1

## SYNOPSIS

- SUBROUTINE ZLAGTM(

  TRANS, N, NRHS, ALPHA, DL, D, DU, X, LDX, BETA, B, LDB )

- CHARACTER

  TRANS

- INTEGER

  LDB, LDX, N, NRHS

- DOUBLE

  PRECISION ALPHA, BETA

- COMPLEX\*16

  B( LDB, \* ), D( \* ), DL( \* ), DU( \* ), X( LDX, \* )

## PURPOSE

ZLAGTM performs a matrix-vector product of the form

## ARGUMENTS

- TRANS (input) CHARACTER\*1

  Specifies the operation applied to A. = 'N':  No transpose, B := alpha \* A \* X + beta \* B\
   \= 'T':  Transpose,    B := alpha \* A\*\*T \* X + beta \* B\
   \= 'C':  Conjugate transpose, B := alpha \* A\*\*H \* X + beta \* B

- N (input) INTEGER

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

- NRHS (input) INTEGER

  The number of right hand sides, i.e., the number of columns of the matrices X and B.

- ALPHA (input) DOUBLE PRECISION

  The scalar alpha.  ALPHA must be 0., 1., or -1.; otherwise, it is assumed to be 0.

- DL (input) COMPLEX\*16 array, dimension (N-1)

  The (n-1) sub-diagonal elements of T.

- D (input) COMPLEX\*16 array, dimension (N)

  The diagonal elements of T.

- DU (input) COMPLEX\*16 array, dimension (N-1)

  The (n-1) super-diagonal elements of T.

- X (input) COMPLEX\*16 array, dimension (LDX,NRHS)

  The N by NRHS matrix X. LDX     (input) INTEGER The leading dimension of the array X.  LDX \>= max(N,1).

- BETA (input) DOUBLE PRECISION

  The scalar beta.  BETA must be 0., 1., or -1.; otherwise, it is assumed to be 1.

- B (input/output) COMPLEX\*16 array, dimension (LDB,NRHS)

  On entry, the N by NRHS matrix B. On exit, B is overwritten by the matrix expression B := alpha \* A \* X + beta \* B.

- LDB (input) INTEGER

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