#include <mpi.h>
#include <iostream>
#include <iomanip>

using namespace std;

int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv) {

    MPI_Init(&argc, &argv);
    int limit{100'000'000};

    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

    int id;
    MPI_Comm_rank(MPI_COMM_WORLD, &id);


    double pi{4};
    double signTerm;
    int skip = 2*(world_size -1);

    if (id > 0) {
       pi = 0;

       int i{id * 2 + 1};
       while (i < limit) {

          if (i%4 == 1) {
              signTerm = 4;
          } else {
              signTerm = -4;
          } 

          pi += signTerm / static_cast<double>(i);

          i += skip;
       }

    }

    double sum{0};
    MPI_Reduce(&pi, &sum, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);

    
    if (id == 0) {
       cout << setprecision(10);
       cout << "Pi is about " << sum << endl;
    }


    MPI_Finalize();

    return 0;
}