mpi'd loop

  boost::mpi::environment env(argc, argv);
  boost::mpi::communicator world;
  
  if (world.rank() == 0) {
    std::ofstream ofile;
    ofile.open("overtraining_20k.txt");

    int workers = world.size() - 1;
    int pending = 0;
    for(int sets = 10000; sets <= 20000; sets+=10)
    {
      int dest = pending + 1;
      if (pending >= workers) {
        //Wait for any worker to finish, they'll be our next destination
        std::string result;
        boost::mpi::status s = world.recv(boost::mpi::any_source, 0, result);
        pending -= 1;
        ofile << result << std::endl;
        //Give this worker more work now that they're done
        dest = s.source();
      }

      world.send(dest, 0, sets);
      pending += 1;
    }

    while (pending > 0) {
      std::string result;
      world.recv(boost::mpi::any_source, 0, result);
      pending -= 1;
      ofile << result << std::endl;
    }

    //Notify all workers we're done so they can exit cleanly
    for (int i = 0; i < workers; i++) {
      world.send(i + 1, 0, -1);
    }

    ofile.close();
  }
  else {
    while (true) {
      int sets;
      world.recv(0, 0, sets);
      if (sets < 0) {
        //Exit message
        break;
      }

      double mean = 0;
      for(int i=0; i<10; i++)
        mean = sallsa_mnist(100, sets, false);
      mean /= (double)10.0;
      std::ostringstream lineOut;
      lineOut << sets << "," << mean;
      world.send(0, 0, lineOut.str());
    }
  }