def main()

in models/official/resnet/resnet_main.py [0:0]


def main(unused_argv):
  params = params_dict.ParamsDict(
      resnet_config.RESNET_CFG, resnet_config.RESNET_RESTRICTIONS)
  params = params_dict.override_params_dict(
      params, FLAGS.config_file, is_strict=True)
  params = params_dict.override_params_dict(
      params, FLAGS.params_override, is_strict=True)

  params = flags_to_params.override_params_from_input_flags(params, FLAGS)

  params.validate()
  params.lock()

  tpu_cluster_resolver = tf.distribute.cluster_resolver.TPUClusterResolver(
      FLAGS.tpu if (FLAGS.tpu or params.use_tpu) else '',
      zone=FLAGS.tpu_zone,
      project=FLAGS.gcp_project)

  if params.use_async_checkpointing:
    save_checkpoints_steps = None
  else:
    save_checkpoints_steps = max(5000, params.iterations_per_loop)
  config = tf.estimator.tpu.RunConfig(
      cluster=tpu_cluster_resolver,
      model_dir=FLAGS.model_dir,
      save_checkpoints_steps=save_checkpoints_steps,
      log_step_count_steps=FLAGS.log_step_count_steps,
      session_config=tf.ConfigProto(
          graph_options=tf.GraphOptions(
              rewrite_options=rewriter_config_pb2.RewriterConfig(
                  disable_meta_optimizer=True))),
      tpu_config=tf.estimator.tpu.TPUConfig(
          iterations_per_loop=params.iterations_per_loop,
          num_shards=params.num_cores,
          per_host_input_for_training=tf.estimator.tpu.InputPipelineConfig
          .PER_HOST_V2))  # pylint: disable=line-too-long

  resnet_classifier = tf.estimator.tpu.TPUEstimator(
      use_tpu=params.use_tpu,
      model_fn=resnet_model_fn,
      config=config,
      params=params.as_dict(),
      train_batch_size=params.train_batch_size,
      eval_batch_size=params.eval_batch_size,
      export_to_tpu=FLAGS.export_to_tpu)

  assert (params.precision == 'bfloat16' or
          params.precision == 'float32'), (
              'Invalid value for precision parameter; '
              'must be bfloat16 or float32.')
  tf.logging.info('Precision: %s', params.precision)
  use_bfloat16 = params.precision == 'bfloat16'

  # Input pipelines are slightly different (with regards to shuffling and
  # preprocessing) between training and evaluation.
  if FLAGS.bigtable_instance:
    tf.logging.info('Using Bigtable dataset, table %s', FLAGS.bigtable_table)
    select_train, select_eval = _select_tables_from_flags()
    imagenet_train, imagenet_eval = [
        imagenet_input.ImageNetBigtableInput(  # pylint: disable=g-complex-comprehension
            is_training=is_training,
            use_bfloat16=use_bfloat16,
            transpose_input=params.transpose_input,
            selection=selection,
            augment_name=FLAGS.augment_name,
            randaug_num_layers=FLAGS.randaug_num_layers,
            randaug_magnitude=FLAGS.randaug_magnitude)
        for (is_training, selection) in [(True,
                                          select_train), (False, select_eval)]
    ]
  else:
    if FLAGS.data_dir == FAKE_DATA_DIR:
      tf.logging.info('Using fake dataset.')
    else:
      tf.logging.info('Using dataset: %s', FLAGS.data_dir)
    imagenet_train, imagenet_eval = [
        imagenet_input.ImageNetInput(  # pylint: disable=g-complex-comprehension
            is_training=is_training,
            data_dir=FLAGS.data_dir,
            transpose_input=params.transpose_input,
            cache=params.use_cache and is_training,
            image_size=params.image_size,
            num_parallel_calls=params.num_parallel_calls,
            include_background_label=(params.num_label_classes == 1001),
            use_bfloat16=use_bfloat16,
            augment_name=FLAGS.augment_name,
            randaug_num_layers=FLAGS.randaug_num_layers,
            randaug_magnitude=FLAGS.randaug_magnitude)
        for is_training in [True, False]
    ]

  steps_per_epoch = params.num_train_images // params.train_batch_size
  eval_steps = params.num_eval_images // params.eval_batch_size

  if FLAGS.mode == 'eval':

    # Run evaluation when there's a new checkpoint
    for ckpt in tf.train.checkpoints_iterator(
        FLAGS.model_dir, timeout=FLAGS.eval_timeout):
      tf.logging.info('Starting to evaluate.')
      try:
        start_timestamp = time.time()  # This time will include compilation time
        eval_results = resnet_classifier.evaluate(
            input_fn=imagenet_eval.input_fn,
            steps=eval_steps,
            checkpoint_path=ckpt)
        elapsed_time = int(time.time() - start_timestamp)
        tf.logging.info('Eval results: %s. Elapsed seconds: %d',
                        eval_results, elapsed_time)

        # Terminate eval job when final checkpoint is reached
        current_step = int(os.path.basename(ckpt).split('-')[1])
        if current_step >= params.train_steps:
          tf.logging.info(
              'Evaluation finished after training step %d', current_step)
          break

      except tf.errors.NotFoundError:
        # Since the coordinator is on a different job than the TPU worker,
        # sometimes the TPU worker does not finish initializing until long after
        # the CPU job tells it to start evaluating. In this case, the checkpoint
        # file could have been deleted already.
        tf.logging.info(
            'Checkpoint %s no longer exists, skipping checkpoint', ckpt)

  else:   # FLAGS.mode == 'train' or FLAGS.mode == 'train_and_eval'
    try:
      current_step = tf.train.load_variable(FLAGS.model_dir,
                                            tf.GraphKeys.GLOBAL_STEP)
    except (TypeError, ValueError, tf.errors.NotFoundError):
      current_step = 0
    steps_per_epoch = params.num_train_images // params.train_batch_size
    tf.logging.info('Training for %d steps (%.2f epochs in total). Current'
                    ' step %d.',
                    params.train_steps,
                    params.train_steps / steps_per_epoch,
                    current_step)

    start_timestamp = time.time()  # This time will include compilation time

    if FLAGS.mode == 'train':
      hooks = []
      if params.use_async_checkpointing:
        try:
          from tensorflow.contrib.tpu.python.tpu import async_checkpoint  # pylint: disable=g-import-not-at-top
        except ImportError as e:
          logging.exception(
              'Async checkpointing is not supported in TensorFlow 2.x')
          raise e

        hooks.append(
            async_checkpoint.AsyncCheckpointSaverHook(
                checkpoint_dir=FLAGS.model_dir,
                save_steps=max(5000, params.iterations_per_loop)))
      if FLAGS.profile_every_n_steps > 0:
        hooks.append(
            tpu_profiler_hook.TPUProfilerHook(
                save_steps=FLAGS.profile_every_n_steps,
                output_dir=FLAGS.model_dir, tpu=FLAGS.tpu)
            )
      resnet_classifier.train(
          input_fn=imagenet_train.input_fn,
          max_steps=params.train_steps,
          hooks=hooks)

    else:
      assert FLAGS.mode == 'train_and_eval'
      while current_step < params.train_steps:
        # Train for up to steps_per_eval number of steps.
        # At the end of training, a checkpoint will be written to --model_dir.
        next_checkpoint = min(current_step + FLAGS.steps_per_eval,
                              params.train_steps)
        resnet_classifier.train(
            input_fn=imagenet_train.input_fn, max_steps=next_checkpoint)
        current_step = next_checkpoint

        tf.logging.info('Finished training up to step %d. Elapsed seconds %d.',
                        next_checkpoint, int(time.time() - start_timestamp))

        # Evaluate the model on the most recent model in --model_dir.
        # Since evaluation happens in batches of --eval_batch_size, some images
        # may be excluded modulo the batch size. As long as the batch size is
        # consistent, the evaluated images are also consistent.
        tf.logging.info('Starting to evaluate.')
        eval_results = resnet_classifier.evaluate(
            input_fn=imagenet_eval.input_fn,
            steps=params.num_eval_images // params.eval_batch_size)
        tf.logging.info('Eval results at step %d: %s',
                        next_checkpoint, eval_results)

      elapsed_time = int(time.time() - start_timestamp)
      tf.logging.info('Finished training up to step %d. Elapsed seconds %d.',
                      params.train_steps, elapsed_time)

    if FLAGS.export_dir is not None:
      # The guide to serve a exported TensorFlow model is at:
      #    https://www.tensorflow.org/serving/serving_basic
      tf.logging.info('Starting to export model.')
      export_path = resnet_classifier.export_saved_model(
          export_dir_base=FLAGS.export_dir,
          serving_input_receiver_fn=imagenet_input.image_serving_input_fn)
      if FLAGS.add_warmup_requests:
        inference_warmup.write_warmup_requests(
            export_path,
            FLAGS.model_name,
            params.image_size,
            batch_sizes=FLAGS.inference_batch_sizes,
            image_format='JPEG')