NAME

dlagtm - perform 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
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).

SunSoft, Inc.  —  Last change: 27 Jun 1995