neighbors.c

很简单的利用mpi在邻居间互相传递数据。

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <mpi.h>



int main(int argc, char **argv)
{
  int i, val1, val2;
  int rank, size, dir;
  int left, right, up, down;
  const int ndim = 2, reorder = 1, disp = 1;
  int dims[ndim], periods[ndim], coords[ndim];
  MPI_Comm MPI_COMM_CART;

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD, &size);

  for(i = 0; i < ndim; i++)
  {
    dims[i] = sqrt(size);
    periods[i] = 1;
  }

  MPI_Cart_create(MPI_COMM_WORLD, ndim, dims, periods, reorder, &MPI_COMM_CART);
  MPI_Comm_rank(MPI_COMM_CART, &rank);
  MPI_Cart_coords(MPI_COMM_CART, rank, ndim, coords);

  dir = 0;
  MPI_Cart_shift(MPI_COMM_CART, dir, disp, &up, &down);
  dir = 1;
  MPI_Cart_shift(MPI_COMM_CART, dir, disp, &left, &right);

  printf("Processor %d, has coords (%d, %d), and neighbors up %d, down %d, left %d, right %d\n",
	 rank, coords[0], coords[1], up, down, left, right);

  if(rank == 0)
    printf("Sending to the right\n");

  val1 = rank;
  MPI_Sendrecv_replace(&val1, 1, MPI_INT, right, 0, left, 0, MPI_COMM_CART,
		       MPI_STATUS_IGNORE);

  if(rank == 0)
	  printf("Sending down\n");

  val2 = rank;
  MPI_Sendrecv_replace(&val2, 1, MPI_INT, right, 0, left, 0, MPI_COMM_CART,
		       MPI_STATUS_IGNORE);

  MPI_Barrier(MPI_COMM_CART);

  if(rank == 0)
	  printf("Done\n");

  MPI_Finalize();

  return EXIT_SUCCESS;
}