
  let mut rng = Xorshiftplus128Rng::new(&mut thread_rng());
  println!("DEBUG: training (CUDA version)...");
  sgd.reset_opt_stats();
  sgd.init_param(&mut rng);
  for iter_nr in 0 .. 1000 {
    sgd.step(&mut train_data);
    if (iter_nr + 1) % 20 == 0 {
      println!("DEBUG: iter: {} stats: {:?}", iter_nr + 1, sgd.get_opt_stats());
      sgd.reset_opt_stats();
    }
  }