test.cc

#include <iostream>
#include <chrono>
#include <thread>
#include <unistd.h>
#include "mpi.h"
using namespace std;

#define db(x) #x << "=" << (x) << " "

int main(int argc, char** argv) {
  MPI_Init(&argc, &argv);
  // int provided;
  // MPI_Init_thread(&argc, &argv, MPI_THREAD_FUNNELED, &provided);
  // cerr << db(provided) << endl;

  int rank, size;
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);
  cerr << db(rank) << db(size) << endl;

  cerr << db(rank) << "posting barrier" << endl;
  MPI_Request barrier;
  MPI_Ibarrier(MPI_COMM_WORLD, &barrier);
  cerr << db(rank) << "posted barrier" << endl;

  sleep(1);
  cerr << db(rank) << "done sleeping" << endl;

  int flag1;
  MPI_Test(&barrier, &flag1, MPI_STATUS_IGNORE);
  cerr << db(rank) << db(flag1) << endl;

  int flag2;
  MPI_Test(&barrier, &flag2, MPI_STATUS_IGNORE);
  cerr << db(rank) << db(flag2) << endl;

  MPI_Wait(&barrier, MPI_STATUS_IGNORE);
  cerr << db(rank) << "done" << endl;

  MPI_Finalize();
  return 0;
}