/*
* mpipi.c
* (c) Neil Gershenfeld  9/1/97
* use MPI to evaluate pi by summation
*/

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

void main(int argc, char** argv) {
	int rank,nproc,tag,i,istart,iend,N;
	double sum,pi;

	tag = 0;
	sum = 0.0;
	N = 100000000;
	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	MPI_Comm_size(MPI_COMM_WORLD, &nproc);
	if (rank == 0) {
	   MPI_Reduce(&sum,&pi,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD);
       printf("Using %d processes, pi = %f\n",nproc,pi);
	} else {
	   istart = 1 + (rank-1)*N/(nproc-1);
	   iend = rank*N/(nproc-1);
	   for (i = istart; i <= iend; ++i)
		   sum += 0.5/((i-0.75)*(i-0.25));
	   MPI_Reduce(&sum,&pi,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD);
	}
	MPI_Finalize();
}