#include "mpi.h"
#include <stdio.h>
#include <math.h>
int main( int argc, char *argv[] )
{
    int n, myid, numprocs, i;
    double PI25DT = 3.141592653589793238462643;
    double mypi, pi, sum;
    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&myid);
    n=atoi(argv[1])*numprocs;
    sum = 0.0;
    for (i = myid ; i < n; i += numprocs) {
        sum += pow((-1),i)*(4.0 / (2*i+1));
	printf("%d,    %d \n", myid, i);
        }
    mypi = sum;
    MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0,
    MPI_COMM_WORLD);
    if (myid == 0)
        printf("pi is approximately %.16f, Error is %.16f\n",pi, fabs(pi - PI25DT));

    MPI_Finalize();
    return 0;
}