Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3  -  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 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*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) 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 auxiliary routine (version 3.3.1)   April 2011                            DLAGTM(3lapack)
```