def inception_model_fn()

in models/experimental/inception/inception_v4.py [0:0]


def inception_model_fn(features, labels, mode, params):
  """Inception v4 model using Estimator API."""
  num_classes = FLAGS.num_classes
  is_training = (mode == tf.estimator.ModeKeys.TRAIN)
  is_eval = (mode == tf.estimator.ModeKeys.EVAL)

  if isinstance(features, dict):
    features = features['feature']

  features = tensor_transform_fn(features, params['model_transpose_dims'])

  # This nested function allows us to avoid duplicating the logic which
  # builds the network, for different values of --precision.
  def build_network():
    if FLAGS.precision == 'bfloat16':
      with contrib_tpu.bfloat16_scope():
        logits, end_points = inception.inception_v4(
            features,
            num_classes,
            is_training=is_training)
      logits = tf.cast(logits, tf.float32)
    elif FLAGS.precision == 'float32':
      logits, end_points = inception.inception_v4(
          features,
          num_classes,
          is_training=is_training)
    return logits, end_points

  if FLAGS.clear_update_collections:
    with arg_scope(inception.inception_v4_arg_scope(
        weight_decay=0.0,
        batch_norm_decay=BATCH_NORM_DECAY,
        batch_norm_epsilon=BATCH_NORM_EPSILON,
        updates_collections=None)):
      logits, end_points = build_network()
  else:
    with arg_scope(inception.inception_v4_arg_scope(
        batch_norm_decay=BATCH_NORM_DECAY,
        batch_norm_epsilon=BATCH_NORM_EPSILON)):
      logits, end_points = build_network()

  predictions = {
      'classes': tf.argmax(input=logits, axis=1),
      'probabilities': tf.nn.softmax(logits, name='softmax_tensor')
  }

  if mode == tf.estimator.ModeKeys.PREDICT:
    return tf.estimator.EstimatorSpec(
        mode=mode,
        predictions=predictions,
        export_outputs={
            'classify': tf.estimator.export.PredictOutput(predictions)
        })

  if mode == tf.estimator.ModeKeys.EVAL and FLAGS.display_tensors and (
      not FLAGS.use_tpu):
    with tf.control_dependencies([
        tf.Print(
            predictions['classes'], [predictions['classes']],
            summarize=FLAGS.eval_batch_size,
            message='prediction: ')
    ]):
      labels = tf.Print(
          labels, [labels], summarize=FLAGS.eval_batch_size, message='label: ')

  one_hot_labels = tf.one_hot(labels, FLAGS.num_classes, dtype=tf.int32)

  if 'AuxLogits' in end_points:
    tf.losses.softmax_cross_entropy(
        onehot_labels=one_hot_labels,
        logits=tf.cast(end_points['AuxLogits'], tf.float32),
        weights=0.4,
        label_smoothing=0.1,
        scope='aux_loss')

  tf.losses.softmax_cross_entropy(
      onehot_labels=one_hot_labels,
      logits=logits,
      weights=1.0,
      label_smoothing=0.1)

  losses = tf.add_n(tf.losses.get_losses())
  l2_loss = []
  for v in tf.trainable_variables():
    tf.logging.info(v.name)
    if 'BatchNorm' not in v.name and 'weights' in v.name:
      l2_loss.append(tf.nn.l2_loss(v))
    tf.logging.info(len(l2_loss))
  loss = losses + WEIGHT_DECAY * tf.add_n(l2_loss)

  initial_learning_rate = FLAGS.learning_rate * FLAGS.train_batch_size / 256
  # Adjust the initial learning rate for warmup
  initial_learning_rate /= (
      FLAGS.learning_rate_decay**((FLAGS.warmup_epochs + FLAGS.cold_epochs) /
                                  FLAGS.learning_rate_decay_epochs))
  final_learning_rate = 0.0001 * initial_learning_rate

  host_call = None
  train_op = None
  if is_training:
    batches_per_epoch = _NUM_TRAIN_IMAGES / FLAGS.train_batch_size
    global_step = tf.train.get_or_create_global_step()
    current_epoch = tf.cast(
        (tf.cast(global_step, tf.float32) / batches_per_epoch), tf.int32)

    clr = FLAGS.cold_learning_rate
    wlr = initial_learning_rate / (FLAGS.warmup_epochs + FLAGS.cold_epochs)
    learning_rate = tf.where(
        tf.greater_equal(current_epoch, FLAGS.cold_epochs), (tf.where(
            tf.greater_equal(current_epoch,
                             FLAGS.warmup_epochs + FLAGS.cold_epochs),
            tf.train.exponential_decay(
                learning_rate=initial_learning_rate,
                global_step=global_step,
                decay_steps=int(FLAGS.learning_rate_decay_epochs *
                                batches_per_epoch),
                decay_rate=FLAGS.learning_rate_decay,
                staircase=True), tf.multiply(
                    tf.cast(current_epoch, tf.float32), wlr))), clr)

    # Set a minimum boundary for the learning rate.
    learning_rate = tf.maximum(
        learning_rate, final_learning_rate, name='learning_rate')

    if FLAGS.optimizer == 'sgd':
      tf.logging.info('Using SGD optimizer')
      optimizer = tf.train.GradientDescentOptimizer(
          learning_rate=learning_rate)
    elif FLAGS.optimizer == 'momentum':
      tf.logging.info('Using Momentum optimizer')
      optimizer = tf.train.MomentumOptimizer(
          learning_rate=learning_rate, momentum=0.9)
    elif FLAGS.optimizer == 'RMS':
      tf.logging.info('Using RMS optimizer')
      optimizer = tf.train.RMSPropOptimizer(
          learning_rate,
          RMSPROP_DECAY,
          momentum=RMSPROP_MOMENTUM,
          epsilon=RMSPROP_EPSILON)
    else:
      tf.logging.fatal('Unknown optimizer:', FLAGS.optimizer)

    if FLAGS.use_tpu:
      optimizer = contrib_tpu.CrossShardOptimizer(optimizer)

    update_ops = tf.get_collection(tf.GraphKeys.UPDATE_OPS)
    with tf.control_dependencies(update_ops):
      train_op = optimizer.minimize(loss, global_step=global_step)
    if FLAGS.moving_average:
      ema = tf.train.ExponentialMovingAverage(
          decay=MOVING_AVERAGE_DECAY, num_updates=global_step)
      variables_to_average = (
          tf.trainable_variables() + tf.moving_average_variables())
      with tf.control_dependencies([train_op]), tf.name_scope('moving_average'):
        train_op = ema.apply(variables_to_average)

    # To log the loss, current learning rate, and epoch for Tensorboard, the
    # summary op needs to be run on the host CPU via host_call. host_call
    # expects [batch_size, ...] Tensors, thus reshape to introduce a batch
    # dimension. These Tensors are implicitly concatenated to
    # [params['batch_size']].
    gs_t = tf.reshape(global_step, [1])
    loss_t = tf.reshape(loss, [1])
    lr_t = tf.reshape(learning_rate, [1])
    ce_t = tf.reshape(current_epoch, [1])

    if not FLAGS.skip_host_call:
      def host_call_fn(gs, loss, lr, ce):
        """Training host call. Creates scalar summaries for training metrics.

        This function is executed on the CPU and should not directly reference
        any Tensors in the rest of the `model_fn`. To pass Tensors from the
        model to the `metric_fn`, provide as part of the `host_call`. See
        https://www.tensorflow.org/api_docs/python/tf/contrib/tpu/TPUEstimatorSpec
        for more information.

        Arguments should match the list of `Tensor` objects passed as the second
        element in the tuple passed to `host_call`.

        Args:
          gs: `Tensor with shape `[batch]` for the global_step
          loss: `Tensor` with shape `[batch]` for the training loss.
          lr: `Tensor` with shape `[batch]` for the learning_rate.
          ce: `Tensor` with shape `[batch]` for the current_epoch.

        Returns:
          List of summary ops to run on the CPU host.
        """
        gs = gs[0]
        with summary.create_file_writer(FLAGS.model_dir).as_default():
          with summary.always_record_summaries():
            summary.scalar('loss', tf.reduce_mean(loss), step=gs)
            summary.scalar('learning_rate', tf.reduce_mean(lr), step=gs)
            summary.scalar('current_epoch', tf.reduce_mean(ce), step=gs)

            return summary.all_summary_ops()

      host_call = (host_call_fn, [gs_t, loss_t, lr_t, ce_t])

  eval_metrics = None
  if is_eval:
    def metric_fn(labels, logits):
      """Evaluation metric function. Evaluates accuracy.

      This function is executed on the CPU and should not directly reference
      any Tensors in the rest of the `model_fn`. To pass Tensors from the model
      to the `metric_fn`, provide as part of the `eval_metrics`. See
      https://www.tensorflow.org/api_docs/python/tf/contrib/tpu/TPUEstimatorSpec
      for more information.

      Arguments should match the list of `Tensor` objects passed as the second
      element in the tuple passed to `eval_metrics`.

      Args:
        labels: `Tensor` with shape `[batch, ]`.
        logits: `Tensor` with shape `[batch, num_classes]`.

      Returns:
        A dict of the metrics to return from evaluation.
      """
      predictions = tf.argmax(logits, axis=1)
      top_1_accuracy = tf.metrics.accuracy(labels, predictions)
      in_top_5 = tf.cast(tf.nn.in_top_k(logits, labels, 5), tf.float32)
      top_5_accuracy = tf.metrics.mean(in_top_5)

      return {
          'accuracy': top_1_accuracy,
          'accuracy@5': top_5_accuracy,
      }

    eval_metrics = (metric_fn, [labels, logits])

  return contrib_tpu.TPUEstimatorSpec(
      mode=mode,
      loss=loss,
      train_op=train_op,
      host_call=host_call,
      eval_metrics=eval_metrics)