/* pi_mpi.c */
#include "mpi.h"
int _myid;
int _numprocs;
MPI_Status _status;

#include <stdio.h>
#define asyncron

double psum( int a, int d, int n ) {
   double h=0.0, pi=0.0, x=0.0;
   int i=0;
   h=1.0/(double)n;
   for(i=a; i<n;i=i+d) { x=h*((double)i-0.5); pi=pi+(4.0/(1.0+x*x)); }
   pi=pi*h;
   return pi;
}

int main(int argc, char *argv[]) {
   double res1=0.0, res2=0.0;
   int n=100000000, step=2, num;
   
   if(MPI_Init(&argc, &argv)) { 
     fprintf(stderr,"error MPI_init\n");
     MPI_Abort(MPI_COMM_WORLD,1);
   }
   MPI_Comm_size(MPI_COMM_WORLD,&_numprocs);
   MPI_Comm_rank(MPI_COMM_WORLD,&_myid);
   fprintf(stderr,"Process %d of %d\n",_myid,_numprocs);
   
   if(_myid==0){ /* MAIN COMPONENT */
     num=0;
     MPI_Send( &n, 1, MPI_INT, 1, 0, MPI_COMM_WORLD );
     MPI_Send( &step, 1, MPI_INT, 1, 0, MPI_COMM_WORLD );
     MPI_Send( &num, 1, MPI_INT, 1, 0, MPI_COMM_WORLD );
     num=1;
     MPI_Send( &n, 1, MPI_INT, 2, 0, MPI_COMM_WORLD );
     MPI_Send( &step, 1, MPI_INT, 2, 0, MPI_COMM_WORLD );
     MPI_Send( &num, 1, MPI_INT, 2, 0, MPI_COMM_WORLD );
     
     MPI_Recv(&res1,1, MPI_DOUBLE ,1,0,MPI_COMM_WORLD, &_status);
     MPI_Recv(&res2,1, MPI_DOUBLE ,2,0,MPI_COMM_WORLD, &_status);
     printf("pi = %f\n", res1+res2);
     MPI_Finalize();
     return 0;
   } /* END MAIN COMPONENT */
   if(_myid==1){ /* COMPONENT */
     MPI_Recv(&n,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     MPI_Recv(&step,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     MPI_Recv(&num,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     res1=psum(num ,step ,n );
     MPI_Send( &res1, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD );
     MPI_Finalize();
     return 0;
   }
   if(_myid==2){ /* COMPONENT */
     MPI_Recv(&n,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     MPI_Recv(&step,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     MPI_Recv(&num,1, MPI_INT ,0, 0,MPI_COMM_WORLD, &_status);
     res2=psum(num ,step ,n );
     MPI_Send( &res2, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD );
     MPI_Finalize();
     return 0;
   }
}