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 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  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.


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.

               (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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