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


int main(int argc, char *argv[]) 
{
  int n, n0, nn, np, me, ier, i;
  double pi, pi0, x, y;
  MPI_Init(&argc,&argv);
  MPI_Comm_size(MPI_COMM_WORLD,&np);
  MPI_Comm_rank(MPI_COMM_WORLD,&me);
  if ( me == 0 ) {
    //
    // Master asks the number of points
    // 
    printf("Enter N \n"); scanf("%d",&n0);
    nn = n0/np;
    n = nn*np;
  }
  //
  // Master broadcasts nn to all others
  //
  MPI_Bcast(&nn,1,MPI_INT,0,MPI_COMM_WORLD);
  printf("me=%d nn=%d\n",me,nn);
  srand(time(NULL)+me);
  pi = 0.0;
  for ( i=0; i<nn; i++ ) {
    x = (double)rand()/RAND_MAX;
    y = (double)rand()/RAND_MAX;
    if ( sqrt( x*x + y*y ) <= 1 )
      pi = pi + 1;
  }
  //
  // Collect sum to master
  //
  MPI_Reduce(&pi,&pi0,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD);
  if ( me==0 ) 
    printf("Monte Carlo approximation to pi= %lf\n",4*pi0/n);
  MPI_Finalize();
}