NAME¶

SLAGTM - 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 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, * )

PURPOSE¶

SLAGTM 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) 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).