dlagtm(3)

NAME

DLAGTM - perform a matrix-vector product of the form B :=

alpha * A * X + beta * B where A is a tridiagonal matrix of or

der N, B and X are N by NRHS matrices, and alpha and beta are re

al 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 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.

ARGUMENTS

TRANS (input) CHARACTER

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 version 3.0 15 June 2000

DLAGTM(3)