# CentOS 7.0 - man page for dlagtm (centos section 3)

```dlagtm.f(3)							      LAPACK							       dlagtm.f(3)

NAME
dlagtm.f -

SYNOPSIS
Functions/Subroutines
subroutine dlagtm (TRANS, N, NRHS, ALPHA, DL, D, DU, X, LDX, BETA, B, LDB)
DLAGTM performs a matrix-matrix product of the form C = aAB+BC, where A is a tridiagonal matrix, B and C are rectangular matrices, and
a and B are scalars, which may be 0, 1, or -1.

Function/Subroutine Documentation
subroutine dlagtm (characterTRANS, integerN, integerNRHS, double precisionALPHA, double precision, dimension( * )DL, double precision,
dimension( * )D, double precision, dimension( * )DU, double precision, dimension( ldx, * )X, integerLDX, double precisionBETA, double
precision, dimension( ldb, * )B, integerLDB)
DLAGTM performs a matrix-matrix product of the form C = aAB+BC, where A is a tridiagonal matrix, B and C are rectangular matrices, and a
and B are scalars, which may be 0, 1, or -1.

Purpose:

DLAGTM 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.

Parameters:
TRANS

TRANS is 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

N is INTEGER
The order of the matrix A.  N >= 0.

NRHS

NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrices X and B.

ALPHA

ALPHA is DOUBLE PRECISION
The scalar alpha.	ALPHA must be 0., 1., or -1.; otherwise,
it is assumed to be 0.

DL

DL is DOUBLE PRECISION array, dimension (N-1)
The (n-1) sub-diagonal elements of T.

D

D is DOUBLE PRECISION array, dimension (N)
The diagonal elements of T.

DU

DU is DOUBLE PRECISION array, dimension (N-1)
The (n-1) super-diagonal elements of T.

X

X is DOUBLE PRECISION array, dimension (LDX,NRHS)
The N by NRHS matrix X.

LDX

LDX is INTEGER
The leading dimension of the array X.  LDX >= max(N,1).

BETA

BETA is DOUBLE PRECISION
The scalar beta.  BETA must be 0., 1., or -1.; otherwise,
it is assumed to be 1.

B

B is 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

LDB is INTEGER
The leading dimension of the array B.  LDB >= max(N,1).

Author:
Univ. of Tennessee

Univ. of California Berkeley