MPI_计算pi值程序

#include "mpi.h"
#include <iostream>
#include <cmath>

using namespace std;

int main(int argc,char* argv[])
{
    double local = 0,pi;
    int rank,size;
    const int N = 100000;

    MPI_Init(&argc,&argv);
    MPI_Comm_rank(MPI_COMM_WORLD,&rank);
    MPI_Comm_size(MPI_COMM_WORLD,&size);

    //通过rank和size参数的使用使每个进程只计算一部分值 *** i+=size设置巧妙
    for(int i=rank;i<N;i+=size)
    {
        local += 4.0/(1.0 + ((i + 0.5)/N) * ((i + 0.5)/N));
    }

    MPI_Reduce(&local,&pi,1,MPI_DOUBLE,MPI_SUM,0,MPI_COMM_WORLD);
    if(rank == 0)
    {
        cout << "pi is " << pi * (1.0 / N) << endl;
    }
    MPI_Finalize();

    return 0;
}