Ticket #6704: allreduce.cpp

#include <iostream>
#include <vector>
#include <algorithm>

#include "boost/mpi.hpp"

int main(int argc, char* argv[]) {
    namespace mpi = boost::mpi;
    mpi::environment env(argc, argv);
    mpi::communicator world;
    std::vector<int> in(10, world.rank());
    std::vector<int> out(10, 0);
    std::vector<int>& sendbuf = argc == 1 ? in : out;

    mpi::all_reduce(world, &(sendbuf[0]), sendbuf.size(), &(out[0]), std::plus<int>());
    int result = 0;
    for (int i = 0; i < world.size(); ++i) {
        result += i;
    }
    for (int i = 0; i < world.size(); ++i) {
        world.barrier();
        if (i == world.rank()) {
            std::cout << "This is P" << i;
            if (std::equal_range(out.begin(), out.end(), result)
                == std::make_pair(out.begin(), out.end())) {
                std::cout << " good\n";
            } else {
                std::cout << " bad ->";
                std::copy(out.begin(), out.end(),
                          std::ostream_iterator<int>(std::cout, " "));
                std:: cout << " instead of " << result << '\n';
            }
        }
    }
    return 0;
}