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 zero, one, or minus one

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, ∗ )

#include <sunperf.h>

void dlagtm(char trans, int n, int nrhs, double alpha, double ∗dl, double ∗d, double ∗du, double ∗dx, int ldx, double dbeta, double ∗db, int ldb) ;

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).

SunOS 5.0  —  Last change: 10 Dec 1998