#include <stdio.h>
#include <mpi.h>
#include <malloc.h>

void main(int argc, char **argv )
 {
  int myid, numprocs;
  int i;
  int iter=10;
  int *a,*b,*c,*d,*e;
  MPI_Status status;

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
  MPI_Comm_rank(MPI_COMM_WORLD,&myid);

  if (numprocs < 3)
   {
    printf("ERROR: This example requires 3 processes\n");
   }
  else
   {
    a = (int *) malloc(iter*sizeof(int));
    b = (int *) malloc(iter*sizeof(int));
    c = (int *) malloc(iter*sizeof(int));
    d = (int *) malloc(iter*sizeof(int));
    for (i=0; i<iter; i++)
     {
      a[i] = i;
      b[i] = i;
     }
    if (myid == 0)
     {
      MPI_Recv(c,10,MPI_INT,1,0,MPI_COMM_WORLD,&status);
      MPI_Recv(d,10,MPI_INT,2,0,MPI_COMM_WORLD,&status);
      e = (int *) malloc(iter*sizeof(int));
      for (i=0; i<iter; i++) 
       { 
        e[i] = d[i] - c[i]; 
        printf("e[%d] = %d\n",i,e[i]); 
       }       
     }
    else if (myid == 1)
     {
      for (i=0; i<iter; i++) { c[i] = a[i] + b[i]; }
      MPI_Send(c,10,MPI_INT,0,0,MPI_COMM_WORLD);
     }
    else if (myid == 2)
     {
      for (i=0; i<iter; i++) { d[i] = a[i] * b[i]; }
      MPI_Send(d,10,MPI_INT,0,0,MPI_COMM_WORLD); 
     }
    else
     {
      printf("Process id %d not needed\n",myid);
     }
   }
  MPI_Finalize();
 }