dmatvec_genr 

Matrix-vector product for general storage by rows (Serial and Parallel Versions)

FORMAT

  DMATVEC_GENR (job, a, ia, ja, nz, w, x, y, n, iparam)

Arguments

  job                 integer*4
                      On entry, defines the operation to be performed:

                      job = 0 : y = A * x

                      job = 1 : y = transp(A) * x

                      job = 2 : y = w - A * x

                      job = 3 : y = w - transp(A) * x
                      On exit, job is unchanged.

  a                   real*8
                      On entry, a one-dimensional array of length at least nz
                      containing the nonzero elements of the matrix A.
                      On exit, a is unchanged.

  ia                  integer*4
                      On entry, a one-dimensional array of length at least
                      n+1,  containing the starting indices of each row in
                      arrays JA and A.
                      On exit, ia is unchanged.

  ja                  integer*4
                      On entry, a one dimensional array of length at least
                      nz, containing the column values of each nonzero
                      element of the matrix A, stored using the general
                      storage by rows scheme.
                      On exit, ja is unchanged.

  nz                  integer*4
                      On entry, the number of nonzero elements stored in
                      array A.
                      On exit, nz is unchanged.

  w                   real*8
                      On entry, a one-dimensional array of length at least n
                      containing the vector w when job = 2 or 3. The elements
                      are accessed with unit increment. When job = 0 or 1,
                      array W is not needed so w can be a dummy parameter.
                      On exit, w is unchanged.

  x                   real*8
                      On entry, a one-dimensional array of length at least n,
                      containing the elements of vector x, accessed with unit
                      increment.
                      On exit, x is unchanged.

  y                   real*8
                      On entry, a one-dimensional array of length at least n.
                      On exit, array Y is overwritten by the output vector y.
                      The elements of array Y are accessed with unit
                      increment.

  n                   integer*4
                      On entry, the order of the matrix A.
                      On exit, n is unchanged.

  iparam              integer*4
                      On entry, a one-dimensional array of length at least 50.
                      The variables in the IPARAM  array are assigned the values
                      listed in Table 10-4 of the CXML Reference Guide.  
                      Of the first 50 values, the 30th - 50th elements in IPARAM
                      are reserved for the use of CXML.

Description

  DMATVEC_GENR obtains the matrix-vector product for a sparse matrix stored
  using the general storage by rows scheme. Depending on the value of the
  input parameter job, either the matrix or its transpose is used in the
  operation.

  This routine is available in both serial and parallel versions. The routine
  names and parameter list are identical for both versions. For information
  about linking to the serial or to the parallel library, refer to the CXML
  Reference Manual.