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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,  dou-
               ble  *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).

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