syncbug.java

MPI for java for Distributed Programming

import mpi.*;

class syncbug {
  static public void main(String[] args) throws MPIException {
    
    int me,tasks,i;
    int SIZE = 4;
    int [] s = new int[SIZE];
    int [] r = new int[SIZE];
    int tag = 87;    
    MPI.Init(args);
    me = MPI.COMM_WORLD.Rank();
    tasks = MPI.COMM_WORLD.Size();
    Request req [] = new Request[SIZE];

    if(me == 0) {
	    
	for(i = 0 ; i<SIZE ; i++) {     
          System.out.println("process "+me +"sending to 1");		
	  req[i] = MPI.COMM_WORLD.Issend(s, 0, SIZE, MPI.INT,1, tag+i);
          System.out.println("process "+me +"sent to 1");		
	}

	for(i=0 ; i<SIZE ; i++) {
          System.out.println("process "+me +"receving 1");		
	  MPI.COMM_WORLD.Recv(r, 0, SIZE, MPI.INT,1,tag+i ); 	    
          System.out.println("process "+me +"received 1");		
	}
	
	for(i=0 ; i<SIZE ; i++) {    
	  req[i].Wait();	
	}
	
    }else { 
	    
	for(i=0 ; i<SIZE ; i++) {    
          System.out.println("process "+me +"sending 0");		
	  req[i] = MPI.COMM_WORLD.Issend(s,0,SIZE,MPI.INT,0,tag+i); 	    
          System.out.println("process "+me +" sent 0");		
	}
	
	for(i=0 ; i<SIZE ; i++) {    
          System.out.println("process "+me +"receiving 0");		
	  MPI.COMM_WORLD.Recv(s,0,SIZE,MPI.INT,0,tag+i); 	    
          System.out.println("process "+me +"received 0");		
	}
	
	for(i=0 ; i<SIZE ; i++) {    
	  req[i].Wait();		
	}
	
    }
    System.out.println("process "+me+" finished");
   MPI.COMM_WORLD.Barrier();    
    MPI.Finalize();
  }
}