Add obviously verifications if all Ranks reached final phase in the p…

…i example

Signed-off-by: Yuki Iwai <[email protected]>

examples/v2beta1/pi/pi.cc

@@ -46,6 +46,7 @@ int main(int argc, char *argv[]) {
  double pi = 4 * (double)total_count / (double)(worker_tests) / (double)(workers);
  printf("pi is approximately %.16lf\n", pi);
  }
+ MPI_Barrier(MPI_COMM_WORLD);
  MPI_Finalize();
  return 0;
 }