NAME

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

CHARACTER TRANS

INTEGER LDB, LDX, N, NRHS

REAL ALPHA, BETA

REAL B( LDB, ∗ ), D( ∗ ), DL( ∗ ), DU( ∗ ), X( LDX, ∗ )

#include <sunperf.h>

void slagtm(char trans, int n, int nrhs, float alpha, float ∗dl, float ∗d, float ∗du, float ∗sx, int ldx, float sbeta, float ∗sb, int ldb) ;

PURPOSE

SLAGTM 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) REAL
The scalar alpha.  ALPHA must be 0., 1., or -1.; otherwise, it is assumed to be 0.

DL (input) REAL array, dimension (N-1)
The (n-1) sub-diagonal elements of T.

D (input) REAL array, dimension (N)
The diagonal elements of T.

DU (input) REAL array, dimension (N-1)
The (n-1) super-diagonal elements of T.

X (input) REAL 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) REAL 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