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## slagtm()

subroutine slagtm | ( | character | trans,
|  | integer | n,
|  | integer | nrhs,
|  | real | alpha,
|  | real, dimension( * ) | dl,
|  | real, dimension( * ) | d,
|  | real, dimension( * ) | du,
|  | real, dimension( ldx, * ) | x,
|  | integer | ldx,
|  | real | beta,
|  | real, dimension( ldb, * ) | b,
|  | integer | ldb )

SLAGTM performs a matrix-matrix product of the form C = αAB+βC, where A is a tridiagonal matrix, B and C are rectangular matrices, and α and β are scalars, which may be 0, 1, or -1.

Download SLAGTM + dependencies [TGZ] [ZIP] [TXT]

Purpose:

      !>
      !> SLAGTM performs a matrix-matrix 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

  [in]

  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
      !>

  [in]

  N

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

  [in]

  NRHS

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

  [in]

  ALPHA

      !>          ALPHA is REAL
      !>          The scalar alpha.  ALPHA must be 0., 1., or -1.; otherwise,
      !>          it is assumed to be 0.
      !>

  [in]

  DL

      !>          DL is REAL array, dimension (N-1)
      !>          The (n-1) sub-diagonal elements of T.
      !>

  [in]

  D

      !>          D is REAL array, dimension (N)
      !>          The diagonal elements of T.
      !>

  [in]

  DU

      !>          DU is REAL array, dimension (N-1)
      !>          The (n-1) super-diagonal elements of T.
      !>

  [in]

  X

      !>          X is REAL array, dimension (LDX,NRHS)
      !>          The N by NRHS matrix X.
      !>

  [in]

  LDX

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

  [in]

  BETA

      !>          BETA is REAL
      !>          The scalar beta.  BETA must be 0., 1., or -1.; otherwise,
      !>          it is assumed to be 1.
      !>

  [in,out]

  B

      !>          B is REAL 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.
      !>

  [in]

  LDB

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

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.