Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - 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 DLAGTM( TRANS, N, NRHS, ALPHA, DL, D, DU, X, LDX, BETA, B, LDB ) CHARACTER TRANS INTEGER LDB, LDX, N, NRHS DOUBLE PRECISION ALPHA, BETA DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ), X( LDX, * )

**PURPOSE**

DLAGTM 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'* X + beta * B = 'C': Conjugate transpose = Transpose 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) DOUBLE PRECISION array, dimension (N-1) The (n-1) sub-diagonal elements of T. D (input) DOUBLE PRECISION array, dimension (N) The diagonal elements of T. DU (input) DOUBLE PRECISION array, dimension (N-1) The (n-1) super-diagonal elements of T. X (input) DOUBLE PRECISION 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) DOUBLE PRECISION 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). LAPACK auxiliary routine (version 3.3.1) April 2011 DLAGTM(3lapack)