[Mpi3-rma] Updated Example 11.21

[James Dinan]

Hi All,

Thanks for the feedback during today's reading.  I've attached updated
code for example 11.21.  Updated lines are marked with a *.  Changes:

- Window size in the comment should have been NSTEPS*N*sizeof(double)
- MPI_STATUS_NULL in waitany errpr fixed with addition of if .. else ..
- s/RGet/Rget/
- compute(..., data[M], ...) -> data[j]
- s/RPut/Rput/

 ~Jim.

---example 11.21---

  int i, j;
  MPI_Win win;
  MPI_Request put_req[M] = { MPI_REQUEST_NULL };
  MPI_Request get_req;
  double data[M][N];

* /* Create win: size NSTEPS*N*sizeof(double), displacement unit
MPI_DOUBLE */

  MPI_Win_lock_all(0, win);

  for (i = 0; i < NSTEPS; i++) {
*   if (i < M)
*     j = i;
*   else
      MPI_Waitany(M, put_req, &j, MPI_STATUS_IGNORE);

*   MPI_Rget(data[j], N, MPI_DOUBLE, target, i*N, N, MPI_DOUBLE, win,
        &get_req);
    MPI_Wait(get_req);
*   compute(i, data[j], ...);
*   MPI_Rput(data[j], N, MPI_DOUBLE, target, i*N, N, MPI_DOUBLE, win,
        &put_req[j]);
}

MPI_Waitall(M, put_req, MPI_STATUSES_IGNORE);
MPI_Win_unlock_all(win);