# clagtm (l) - Linux Man Pages

## NAME

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

CHARACTER TRANS

INTEGER LDB, LDX, N, NRHS

REAL ALPHA, BETA

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

## PURPOSE

CLAGTM performs a matrix-vector product of the form

## ARGUMENTS

TRANS (input) CHARACTER*1
Specifies the operation applied to A. = aqNaq: No transpose, B := alpha * A * X + beta * B
= aqTaq: Transpose, B := alpha * A**T * X + beta * B
= aqCaq: 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) REAL
The scalar alpha. ALPHA must be 0., 1., or -1.; otherwise, it is assumed to be 0.
DL (input) COMPLEX array, dimension (N-1)
The (n-1) sub-diagonal elements of T.
D (input) COMPLEX array, dimension (N)
The diagonal elements of T.
DU (input) COMPLEX array, dimension (N-1)
The (n-1) super-diagonal elements of T.
X (input) COMPLEX 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) REAL
The scalar beta. BETA must be 0., 1., or -1.; otherwise, it is assumed to be 1.
B (input/output) COMPLEX 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).