DLAGTM (3lapack)

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 (3lapack)
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
          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).



CXML Home Page

Index of CXML Routines