map.java

MPI for java for Distributed Programming

package mpi.topo; 
/****************************************************************************

 MPI-Java version :
    Sung-Hoon Ko([e-mail])
    Northeast Parallel Architectures Center at Syracuse University
    03/22/98

****************************************************************************/

import mpi.*;
 
 
public class map {
  static public void main(String[] args) throws MPIException {
  }

  public map() {
  }

  public map(String[] args) throws Exception {

    final int NUM_DIMS = 2;
    int       rank, size, i;
    int       errors=0;
    int        dims[] = new int[NUM_DIMS];
    boolean periods[] = new boolean[NUM_DIMS];
    int       new_rank;

    MPI.Init(args);
    rank = MPI.COMM_WORLD.Rank();
    size = MPI.COMM_WORLD.Size(); 
    
    if(size != 8) {
      if(rank == 0) {	    
        System.out.println("topo->map must run with 8 tasks!");
      }
      MPI.Finalize();
      return;
    }

    /* Clear dims array and get dims for topology */
    for(i=0;i<NUM_DIMS;i++) { dims[i] = 0; periods[i] = false; }
    dims[0] = 2;
    dims[1] = 4;
    
    //Cartcomm.Dims_create(size,dims);

    Cartcomm intcomm = MPI.COMM_WORLD.Create_cart(dims,periods,false);

    /* Look at what rankings a cartesian topology MIGHT have */
    new_rank = intcomm.Map(dims, periods);

    /* Check that all new ranks are used exactly once */
    int rbuf[] = new int[size];
    int sbuf[] = new int[size];

    for (i=0; i<size; i++) 
      sbuf[i] = 0;
    sbuf[new_rank] = 1;
    MPI.COMM_WORLD.Reduce(sbuf,0,rbuf,0,size,MPI.INT,MPI.SUM,0);
    if (rank == 0) {
      for (i=0; i<size; i++) {
	if (rbuf[i] != 1) {
	  errors++;
	  System.out.println("Rank "+i+" used "+rbuf[i]+" times");
	}
      }
      if (errors == 0) 
	System.out.println( "Map test passed\n" );
    }
    
    MPI.Finalize();
  }
}