# Copyright 2019 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Tests mixed precision works correctly with Keras layers and models."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import tensorflow as tf

import os

from absl import flags
from absl.testing import parameterized
import numpy as np
from keras import backend
from keras import combinations
from keras import keras_parameterized
from keras import layers
from keras import models
from keras import optimizer_v1
from keras import testing_utils
from keras.engine import base_layer
from keras.engine import base_layer_utils
from keras.engine import input_spec
from keras.engine import sequential
from keras.layers import core
from keras.mixed_precision import get_layer_policy
from keras.mixed_precision import loss_scale_optimizer
from keras.mixed_precision import policy
from keras.mixed_precision import test_util as mp_test_util
from keras.optimizer_v2 import gradient_descent
from keras.saving import save
from keras.utils import generic_utils


# Pylint's static analysis incorrectly believes many layers are non-callable, so
# we disable the lint error.
# pylint: disable=not-callable


class MultiplyLayerWithoutAutoCast(mp_test_util.MultiplyLayer):
  """Same as MultiplyLayer, but does not use AutoCastVariables."""

  def build(self, _):
    dtype = self.dtype
    if dtype in ('float16', 'bfloat16'):
      dtype = 'float32'
    self.v = self.add_weight(
        'v', (),
        initializer='ones',
        dtype=dtype,
        experimental_autocast=False,
        regularizer=self._regularizer)
    self.built = True

  def call(self, inputs):
    self.assert_input_types(inputs)
    assert self.v.dtype in (tf.float32, tf.float64)
    return self._multiply(inputs, tf.cast(self.v, inputs.dtype))


class MultiplyLayerWithFunction(mp_test_util.MultiplyLayer):
  """Same as MultiplyLayer, but _multiply is decorated with a tf.function."""

  @tf.function
  def _multiply(self, x, y):
    return super(MultiplyLayerWithFunction, self)._multiply(x, y)


# If called outside any strategy.scope() calls, this will return the default
# strategy.
default_strategy_fn = tf.distribute.get_strategy


def create_mirrored_strategy():
  """Create a MirroredStrategy, using a GPU if it is available."""
  if tf.config.list_logical_devices('GPU'):
    return tf.distribute.MirroredStrategy(['cpu:0', 'gpu:0'])
  else:
    return tf.distribute.MirroredStrategy(['cpu:0'])


def create_central_storage_strategy():
  """Create a CentralStorageStrategy, using a GPU if it is available."""
  compute_devices = ['cpu:0', 'gpu:0'] if (
      tf.config.list_logical_devices('GPU')) else ['cpu:0']
  return tf.distribute.experimental.CentralStorageStrategy(
      compute_devices, parameter_device='cpu:0')


TESTCASES = ({
    'testcase_name': 'base',
    'strategy_fn': default_strategy_fn
}, {
    'testcase_name': 'distribute',
    'strategy_fn': create_mirrored_strategy
})


@combinations.generate(combinations.combine(mode=['graph', 'eager']))
class KerasLayerTest(keras_parameterized.TestCase):
  """Test mixed precision with Keras layers."""

  @parameterized.named_parameters(*TESTCASES)
  def test_mixed_policies_(self, strategy_fn):
    strategy = strategy_fn()
    for dtype in 'float16', 'bfloat16':
      x = tf.constant([1.])
      policy_name = 'mixed_' + dtype
      with strategy.scope(), policy.policy_scope(policy_name):
        layer = mp_test_util.MultiplyLayer(assert_type=dtype)
        self.assertEqual(layer.dtype, tf.float32)
        self.assertEqual(get_layer_policy.get_layer_policy(layer).name,
                         policy_name)
        y = layer(x)
        self.assertEqual(layer.v.dtype, tf.float32)
        self.assertEqual(y.dtype, dtype)
        self.assertEqual(layer.dtype_policy.name, policy_name)
        self.assertIsInstance(layer.dtype_policy, policy.Policy)
        self.assertEqual(layer.compute_dtype, dtype)
        self.assertEqual(layer.dtype, tf.float32)
        self.assertEqual(layer.variable_dtype, tf.float32)
        self.assertEqual(get_layer_policy.get_layer_policy(layer).name,
                         policy_name)
        self.evaluate(tf.compat.v1.global_variables_initializer())
        self.assertEqual(self.evaluate(y), 1.)

  def test_layer_with_int_variable(self):
    class LayerWithIntVar(base_layer.Layer):

      def build(self, _):
        self.v = self.add_weight('v', dtype='int32', trainable=False)

      def call(self, inputs):
        # Only float variables should be autocasted. This will fail if self.v is
        # autocasted to float32
        return tf.cast(inputs, 'int32') + self.v

    x = tf.constant([1.])
    layer = LayerWithIntVar(dtype=policy.Policy('mixed_float16'))
    self.assertEqual(layer(x).dtype, 'int32')

  @parameterized.named_parameters(*TESTCASES)
  def test_layer_with_non_autocast_variable(self, strategy_fn):
    x = tf.constant([1.])
    with strategy_fn().scope():
      with policy.policy_scope('mixed_float16'):
        layer = MultiplyLayerWithoutAutoCast(assert_type=tf.float16)
        y = layer(x)
        self.assertEqual(layer.v.dtype, tf.float32)
        self.assertEqual(y.dtype, tf.float16)
        self.evaluate(tf.compat.v1.global_variables_initializer())
        self.assertEqual(self.evaluate(y), 1.)

  @parameterized.named_parameters(*TESTCASES)
  def test_layer_calling_tf_function(self, strategy_fn):
    x = tf.constant([1.])
    with strategy_fn().scope():
      with policy.policy_scope('mixed_float16'):
        layer = MultiplyLayerWithFunction(assert_type=tf.float16)
        y = layer(x)
        self.assertEqual(layer.v.dtype, tf.float32)
        self.assertEqual(y.dtype, tf.float16)
        self.evaluate(tf.compat.v1.global_variables_initializer())
        self.assertEqual(self.evaluate(y), 1.)

  @parameterized.named_parameters(*TESTCASES)
  def test_layer_regularizer_runs_in_var_dtype(self, strategy_fn):
    x = tf.constant([1.])
    with strategy_fn().scope():
      with policy.policy_scope('mixed_float16'):
        # Test on MultiplyLayer
        layer = mp_test_util.MultiplyLayer(
            assert_type=tf.float16,
            regularizer=mp_test_util.IdentityRegularizer())
        layer(x)
        (regularizer_loss,) = layer.losses
        self.assertEqual(regularizer_loss.dtype, tf.float32)
        self.evaluate(tf.compat.v1.global_variables_initializer())
        self.assertEqual(self.evaluate(regularizer_loss), 1.)

        # Test on MultiplyLayerWithoutAutoCast
        layer = MultiplyLayerWithoutAutoCast(
            assert_type=tf.float16,
            regularizer=mp_test_util.IdentityRegularizer())
        layer(x)
        (regularizer_loss,) = layer.losses
        self.assertEqual(regularizer_loss.dtype, tf.float32)
        self.evaluate(tf.compat.v1.global_variables_initializer())
        self.assertEqual(self.evaluate(regularizer_loss), 1.)

  @parameterized.named_parameters(*TESTCASES)
  def test_passing_policy_to_layer(self, strategy_fn):
    x = tf.constant([1.], dtype=tf.float16)
    with strategy_fn().scope():
      # Passing a Policy to 'dtype' sets the policy for that layer.
      layer = mp_test_util.MultiplyLayer(
          assert_type=tf.float16, dtype=policy.Policy('mixed_float16'))
      # layer.dtype refers to the variable dtype
      self.assertEqual(layer.dtype, tf.float32)
      layer(x)
      self.assertEqual(layer.v.dtype, tf.float32)
      with policy.policy_scope('mixed_float16'):
        # Passing a Policy to dtype overrides the global Policy
        layer = mp_test_util.MultiplyLayer(
            assert_type=tf.float64, dtype=policy.Policy('float64'))
        self.assertEqual(layer.dtype_policy.name, 'float64')
        self.assertIsInstance(layer.dtype_policy, policy.Policy)
        self.assertEqual(layer.compute_dtype, tf.float64)
        self.assertEqual(layer.dtype, tf.float64)
        self.assertEqual(layer.variable_dtype, tf.float64)
        self.assertEqual(layer(x).dtype, tf.float64)
        self.assertEqual(layer.v.dtype, tf.float64)

  def test_error_passing_policy_string_to_layer(self):
    with self.assertRaisesRegex(
        TypeError, "Cannot convert value 'mixed_float16' to a "
        'TensorFlow DType'):
      # This is not allowed, as otherwise a "mixed_float16" policy could be
      # created without an API call that has the name "experimental" in it.
      mp_test_util.MultiplyLayer(dtype='mixed_float16')

  @parameterized.named_parameters(*TESTCASES)
  def test_gradient(self, strategy_fn):
    x = tf.constant([1.])
    with strategy_fn().scope() as strategy:
      with policy.policy_scope('mixed_float16'):
        layer = mp_test_util.MultiplyLayer(assert_type=tf.float16)
        # Learning rate is small enough that if applied to a float16 variable,
        # the variable will not change. So this tests the learning rate is not
        # applied to a float16 value, but instead the float32 variable.
        opt = gradient_descent.SGD(2**-14)

        def run_fn():
          with tf.GradientTape() as tape:
            y = layer(x)
            # Divide by num_replicas_in_sync, as the effective total loss is the
            # sum of each of the replica's losses.
            y /= strategy.num_replicas_in_sync

          grad = tape.gradient(y, layer.v)
          return opt.apply_gradients([(grad, layer.v)])

        op = strategy.experimental_run(run_fn)
        if not tf.executing_eagerly():
          self.evaluate(tf.compat.v1.global_variables_initializer())
          self.evaluate(op)
        # The gradient with respective to the variable is 1. Since the
        # variable is initialized with 1 and the learning rate is 2**-14, the
        # new variable value should be: init_val - gradient * learning_rate,
        # which is  1 - 1 * 2**-14
        self.assertEqual(self.evaluate(layer.v), 1 - 2**-14)

  def _test_checkpointing_layer_weights(self, strategy_fn,
                                        mixed_prec_when_saving,
                                        mixed_prec_when_loading):
    # In this test, we potentially save with mixed precision enabled and load
    # with mixed precision disabled, or vice versa. This is possible because
    # variables are float32 regardless of whether mixed precision is enabled.
    save_policy = 'mixed_float16' if mixed_prec_when_saving else 'float32'
    load_policy = 'mixed_float16' if mixed_prec_when_loading else 'float32'
    save_input_dtype = 'float16' if mixed_prec_when_saving else 'float32'
    load_input_dtype = 'float16' if mixed_prec_when_loading else 'float32'

    # Create a layer and save a checkpoint.
    x = tf.constant([1.])
    with strategy_fn().scope():
      with policy.policy_scope(save_policy):
        layer = mp_test_util.MultiplyLayer(assert_type=save_input_dtype)
        layer(x)  # Build layer
    layer.set_weights([np.array(100.)])
    self.assertEqual(self.evaluate(layer(x)), 100.)
    checkpoint = tf.train.Checkpoint(layer=layer)
    prefix = os.path.join(self.get_temp_dir(), 'ckpt')
    save_path = checkpoint.save(prefix)

    # Create a new layer and restore the checkpoint.
    x = tf.constant([1.])
    with strategy_fn().scope():
      with policy.policy_scope(load_policy):
        layer = mp_test_util.MultiplyLayer(assert_type=load_input_dtype)
        layer(x)  # Build layer
    layer.set_weights([np.array(200.)])
    self.assertEqual(self.evaluate(layer(x)), 200.)
    checkpoint = tf.train.Checkpoint(layer=layer)
    checkpoint.restore(save_path).assert_consumed().run_restore_ops()
    self.assertEqual(layer.get_weights(), [100.])
    self.assertEqual(self.evaluate(layer(x)), 100.)

  @parameterized.named_parameters(*TESTCASES)
  def test_checkpointing_layer_weights(self, strategy_fn):
    with self.test_session():
      self._test_checkpointing_layer_weights(
          strategy_fn, mixed_prec_when_saving=True,
          mixed_prec_when_loading=True)
      self._test_checkpointing_layer_weights(
          strategy_fn, mixed_prec_when_saving=True,
          mixed_prec_when_loading=False)
      self._test_checkpointing_layer_weights(
          strategy_fn, mixed_prec_when_saving=False,
          mixed_prec_when_loading=True)

  @parameterized.named_parameters(*TESTCASES)
  def test_config(self, strategy_fn):
    x = tf.constant([1.], dtype=tf.float16)
    with strategy_fn().scope():
      for layer, dtype in (
          (mp_test_util.MultiplyLayer(), 'float32'),
          (mp_test_util.MultiplyLayer(dtype='float64'), 'float64'),
          (mp_test_util.MultiplyLayer(dtype=policy.Policy('float64')),
           'float64')):
        config = layer.get_config()
        self.assertEqual(config['dtype'], dtype)
        self.assertIsInstance(config['dtype'], str)
        layer = mp_test_util.MultiplyLayer.from_config(config)
        self.assertEqual(layer.dtype, dtype)
        self.assertEqual(layer(x).dtype, dtype)
        self.assertEqual(layer.v.dtype, dtype)

      layer = mp_test_util.MultiplyLayer(dtype=policy.Policy('mixed_float16'))
      config = layer.get_config()
      self.assertEqual(config['dtype'],
                       {'class_name': 'Policy',
                        'config': {'name': 'mixed_float16'}})
      layer = mp_test_util.MultiplyLayer.from_config(config)
      self.assertEqual(layer.dtype, 'float32')
      self.assertEqual(layer(x).dtype, 'float16')
      self.assertEqual(layer.v.dtype, 'float32')
      config = layer.get_config()
      self.assertEqual(config['dtype'],
                       {'class_name': 'Policy',
                        'config': {'name': 'mixed_float16'}})

      layer = mp_test_util.MultiplyLayer(dtype=policy.Policy('_infer'))
      config = layer.get_config()
      self.assertIsNone(config['dtype'])
      layer = mp_test_util.MultiplyLayer.from_config(config)
      # If a layer is serialized with the "_infer" policy, when deserialized
      # into TF 2 it will have the global policy instead of "_infer". This is
      # because "_infer" is serialized into None, and passing dtype=None in
      # TensorFlow 2 indicates to use the global policy.
      self.assertEqual(layer.dtype, 'float32')
      self.assertEqual(layer(x).dtype, 'float32')
      self.assertEqual(layer.v.dtype, 'float32')

  @parameterized.named_parameters(*TESTCASES)
  def test_config_policy_v1(self, strategy_fn):
    x = tf.constant([1.], dtype=tf.float16)
    with strategy_fn().scope():

      layer = mp_test_util.MultiplyLayer(dtype=policy.PolicyV1('mixed_float16',
                                                               loss_scale=None))
      config = layer.get_config()
      self.assertEqual(config['dtype'],
                       {'class_name': 'PolicyV1',
                        'config': {'name': 'mixed_float16',
                                   'loss_scale': None}})
      layer = mp_test_util.MultiplyLayer.from_config(config)
      self.assertEqual(layer.dtype, 'float32')
      self.assertEqual(layer(x).dtype, 'float16')
      self.assertEqual(layer.v.dtype, 'float32')
      # Restoring a PolicyV1 silently converts it to a Policy and drops the loss
      # scale.
      self.assertEqual(type(layer.dtype_policy), policy.Policy)
      config = layer.get_config()
      # The loss_scale is silently dropped
      self.assertEqual(config['dtype'],
                       {'class_name': 'Policy',
                        'config': {'name': 'mixed_float16'}})

      layer = mp_test_util.MultiplyLayer(dtype=policy.PolicyV1('float64',
                                                               loss_scale=2.))
      config = layer.get_config()
      self.assertEqual(config['dtype'],
                       {'class_name': 'PolicyV1',
                        'config': {'name': 'float64',
                                   'loss_scale': {
                                       'class_name': 'FixedLossScale',
                                       'config': {'loss_scale_value': 2.0}}}})
      layer = mp_test_util.MultiplyLayer.from_config(config)
      self.assertEqual(layer.dtype, 'float64')
      self.assertEqual(layer(x).dtype, 'float64')
      self.assertEqual(layer.v.dtype, 'float64')
      self.assertEqual(type(layer.dtype_policy), policy.Policy)
      config = layer.get_config()
      self.assertEqual(config['dtype'], 'float64')

      layer = mp_test_util.MultiplyLayer(dtype=policy.PolicyV1('_infer',
                                                               loss_scale=2.))
      config = layer.get_config()
      self.assertEqual(config['dtype'],
                       {'class_name': 'PolicyV1',
                        'config': {'name': '_infer',
                                   'loss_scale': {
                                       'class_name': 'FixedLossScale',
                                       'config': {'loss_scale_value': 2.0}}}})
      layer = mp_test_util.MultiplyLayer.from_config(config)
      self.assertEqual(layer.dtype, None)
      self.assertEqual(layer(x).dtype, 'float16')
      self.assertEqual(layer.v.dtype, 'float16')
      self.assertEqual(type(layer.dtype_policy), policy.Policy)
      config = layer.get_config()
      self.assertEqual(config['dtype'], 'float16')

  def test_delete_variable(self):
    layer = base_layer.Layer(dtype=policy.Policy('mixed_float16'))
    layer.x = layer.add_weight('x')
    self.assertEqual(layer.trainable_weights, [layer.x])
    del layer.x
    self.assertEqual(layer.trainable_weights, [])

  def test_build_and_call_layer_in_function(self):
    layer = mp_test_util.MultiplyLayer(dtype=policy.Policy('mixed_float16'))
    @tf.function
    def f():
      return layer(1.)
    y = f()
    self.evaluate(tf.compat.v1.global_variables_initializer())
    self.assertEqual(y.dtype, 'float16')
    self.assertEqual(layer.v.dtype, 'float32')
    self.assertEqual(self.evaluate(y), 1.)

  def test_unsupported_strategy(self):
    strategy = create_central_storage_strategy()
    with strategy.scope(), self.assertRaisesRegex(
        ValueError, 'Mixed precision is not supported with the '
        'tf.distribute.Strategy: CentralStorageStrategy. Either '
        'stop using mixed precision by removing the use of the '
        '"mixed_float16" policy or use a different Strategy, e.g. '
        'a MirroredStrategy.'):
      mp_test_util.MultiplyLayer(dtype=policy.Policy('mixed_float16'))
    # Non-mixed policies are fine
    mp_test_util.MultiplyLayer(dtype=policy.Policy('float64'))


class KerasModelTest(keras_parameterized.TestCase):
  """Test mixed precision with Keras models."""

  def _skip_if_strategy_unsupported(self, strategy_fn):
    if (strategy_fn != default_strategy_fn and
        testing_utils.get_model_type() == 'subclass'):
      self.skipTest('Non-default strategies are unsupported with subclassed '
                    'models')

  def _skip_if_save_format_unsupported(self, save_format):
    model_type = testing_utils.get_model_type()
    if save_format == 'h5' and model_type == 'subclass':
      self.skipTest('Saving subclassed models with the HDF5 format is '
                    'unsupported')
    if (save_format == 'tf' and model_type == 'subclass' and
        not tf.executing_eagerly()):
      self.skipTest('b/148820505: This combination of features is currently '
                    'broken.')

  @keras_parameterized.run_with_all_model_types
  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'operator',
          'strategy_fn': create_mirrored_strategy,
          'use_operator': True
      }, {
          'testcase_name': 'regularizer',
          'strategy_fn': create_mirrored_strategy,
          'use_regularizer': True
      }, {
          'testcase_name': 'get_config',
          'strategy_fn': create_mirrored_strategy,
          'get_config': True,
          'use_regularizer': True,
      }, {
          'testcase_name': 'saved_model',
          'strategy_fn': default_strategy_fn,
          'save_format': 'tf',
          'use_regularizer': True,
      }, {
          'testcase_name': 'saved_model_input_spec',
          'strategy_fn': default_strategy_fn,
          'save_format': 'tf',
          'use_regularizer': True,
          'use_input_spec': True,
      }, {
          'testcase_name': 'h5',
          'strategy_fn': default_strategy_fn,
          'save_format': 'h5',
          'use_regularizer': True,
      }, {
          'testcase_name': 'saved_model_distribute',
          'strategy_fn': create_mirrored_strategy,
          'save_format': 'tf',
          'use_regularizer': True,
      }, {
          'testcase_name': 'saved_model_input_spec_distribute',
          'strategy_fn': create_mirrored_strategy,
          'save_format': 'tf',
          'use_regularizer': True,
          'use_input_spec': True,
      }, {
          'testcase_name': 'h5_distribute',
          'strategy_fn': create_mirrored_strategy,
          'save_format': 'h5',
          'use_regularizer': True,
      }, {
          'testcase_name': 'saved_model_v1_policy',
          'strategy_fn': create_mirrored_strategy,
          'use_v1_policy': True,
          'save_format': 'tf',
      })
  def test_model(self,
                 strategy_fn,
                 use_operator=False,
                 use_regularizer=False,
                 policy_name='mixed_float16',
                 get_config=False,
                 save_format=None,
                 use_input_spec=False,
                 use_v1_policy=False):
    self._skip_if_strategy_unsupported(strategy_fn)
    self._skip_if_save_format_unsupported(save_format)
    if use_regularizer:
      weight_regularizer = mp_test_util.IdentityRegularizer()
      activity_regularizer = mp_test_util.ReduceSumRegularizer()
    else:
      weight_regularizer = activity_regularizer = None
    with strategy_fn().scope():
      cls = policy.PolicyV1 if use_v1_policy else policy.Policy
      with policy.policy_scope(cls(policy_name)):
        layer = mp_test_util.MultiplyLayer(
            assert_type=tf.float16,
            use_operator=use_operator,
            regularizer=weight_regularizer,
            activity_regularizer=activity_regularizer,
            input_shape=(1,))
        if use_input_spec:
          layer.input_spec = input_spec.InputSpec(shape=(None, 1))
        model = testing_utils.get_model_from_layers([layer], input_shape=(1,),
                                                    input_dtype=tf.float16)
        if get_config:
          config = model.get_config()
          model = model.__class__.from_config(
              config,
              custom_objects={'MultiplyLayer': mp_test_util.MultiplyLayer})
          (layer,) = (layer for layer in model.layers
                      if isinstance(layer, mp_test_util.MultiplyLayer))

        def loss_fn(y_true, y_pred):
          del y_true
          return tf.reduce_mean(y_pred)

        # Learning rate is small enough that if applied to a float16 variable,
        # the variable will not change. So this tests the learning rate not
        # applied to a float16 value, but instead the float32 variable.
        opt = gradient_descent.SGD(2**-14)
        # Use a fixed loss scale, as this test will fail if gradients are
        # skipped for a step due to dynamic loss scaling.
        opt = loss_scale_optimizer.LossScaleOptimizer(opt, dynamic=False,
                                                      initial_scale=8)
        model.compile(
            opt,
            loss=loss_fn,
            run_eagerly=testing_utils.should_run_eagerly())

    x = np.ones((2, 1))
    y = np.ones((2, 1))
    dataset = tf.data.Dataset.from_tensor_slices((x, y)).batch(2)
    model.fit(dataset)
    # Variable starts at 1, and should have gradient of 2 ** -14 subtracted
    # from it.
    expected = 1 - 2**-14
    if use_regularizer:
      # Weight and activity regularizer each add another 2 ** -14 to the
      # gradient.
      expected -= 2 * 2**-14
    self.assertEqual(backend.eval(layer.v), expected)

    if save_format:
      with generic_utils.CustomObjectScope(
          {'MultiplyLayer': mp_test_util.MultiplyLayer, 'loss_fn': loss_fn}):
        self._test_saving(model, dataset, save_format, use_regularizer)

  def _test_saving(self, model, dataset, save_format, use_regularizer):
    # Save and load model, asserting variable does not change
    save_path = os.path.join(self.get_temp_dir(), 'model')
    model.save(save_path, save_format=save_format)
    model = save.load_model(save_path)
    (layer,) = (layer for layer in model.layers
                if 'MultiplyLayer' in layer.__class__.__name__)
    expected = 1 - 2**-14
    if use_regularizer:
      expected -= 2 * 2**-14
    self.assertEqual(backend.eval(layer.v), expected)

    # Continue training, and assert variable is correct value
    model.fit(dataset)
    new_expected = expected - 2 ** -14
    if use_regularizer:
      new_expected -= 2 * 2 ** -14
    self.assertEqual(backend.eval(layer.v), new_expected)

    # Load saved model again, and assert variable is previous value
    model = save.load_model(save_path)
    (layer,) = (layer for layer in model.layers
                if 'MultiplyLayer' in layer.__class__.__name__)
    self.assertEqual(backend.eval(layer.v), expected)

    # Ensure various dtype-related aspects of the layer are correct
    self.assertEqual(layer.dtype, 'float32')
    self.assertEqual(get_layer_policy.get_layer_policy(layer).name,
                     'mixed_float16')
    self.assertEqual(layer.v.dtype, 'float32')
    self.assertEqual(layer(np.ones((2, 1))).dtype, 'float16')

    # Loading a model always loads with a v2 Policy, even if saved with a
    # PolicyV1.
    self.assertEqual(type(model.dtype_policy), policy.Policy)
    self.assertEqual(layer.get_config()['dtype'],
                     {'class_name': 'Policy', 'config': {
                         'name': 'mixed_float16'}})

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      })
  def test_fixed_loss_scaling(self,
                              strategy_fn):
    # Note: We do not test mixed precision in this method, only loss scaling.
    loss_scale = 8.
    batch_size = 4
    with strategy_fn().scope():
      x = layers.Input(shape=(1,), batch_size=batch_size)
      layer = mp_test_util.MultiplyLayer()
      y = layer(x)

      # The gradient of 'y' at this point is 1. With loss scaling, the gradient
      # is 'loss_scale'. We divide by the batch size since the loss is averaged
      # across batch elements.
      expected_gradient = loss_scale / batch_size
      identity_with_grad_check_fn = (
          mp_test_util.create_identity_with_grad_check_fn([expected_gradient]))
      y = core.Lambda(identity_with_grad_check_fn)(y)
      model = models.Model(inputs=x, outputs=y)

      def loss_fn(y_true, y_pred):
        del y_true
        return tf.reduce_mean(y_pred)

      opt = gradient_descent.SGD(1.)
      opt = loss_scale_optimizer.LossScaleOptimizer(opt, dynamic=False,
                                                    initial_scale=loss_scale)
      model.compile(
          opt,
          loss=loss_fn,
          run_eagerly=testing_utils.should_run_eagerly())

    self.assertEqual(backend.eval(layer.v), 1)
    x = np.ones((batch_size, 1))
    y = np.ones((batch_size, 1))
    dataset = tf.data.Dataset.from_tensor_slices((x, y)).batch(batch_size)
    model.fit(dataset)
    # Variable starts at 1, and should have gradient of 1 subtracted from it.
    expected = 0
    self.assertEqual(backend.eval(layer.v), expected)

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'loss_scaling',
          'strategy_fn': create_mirrored_strategy,
          'use_loss_scaling': True
      })
  def test_advanced_model(self, strategy_fn, use_loss_scaling=False):
    # The advanced model tests mixed-precision-related features that would occur
    # in a resnet50 model. It tests a model that has:
    #  * Multiple layers, some which use auto-cast variables and some which do
    #    not
    #  * Regularization on some variables and not others.
    #  * A fixed loss scale (if use_loss_scaling is True)

    strategy = strategy_fn()
    if use_loss_scaling:
      loss_scale = 8.
    learning_rate = 2**-14

    with strategy.scope():
      with policy.policy_scope(policy.Policy('mixed_float16')):
        x = layers.Input(shape=(1,), batch_size=2)
        layer1 = mp_test_util.MultiplyLayer(
            assert_type=tf.float16,
            regularizer=mp_test_util.IdentityRegularizer(),
            use_operator=True)
        layer2 = MultiplyLayerWithoutAutoCast(
            assert_type=tf.float16, use_operator=True)
        layer3 = mp_test_util.MultiplyLayer(assert_type=tf.float16,
                                            use_operator=False)
        layer4 = MultiplyLayerWithoutAutoCast(
            assert_type=tf.float16,
            regularizer=mp_test_util.IdentityRegularizer(),
            use_operator=False)
        y = layer1(x)
        y = layer2(y)
        y = layer3(y)
        y = layer4(y)
        if use_loss_scaling:
          # The gradient of 'y' at this point is 1. With loss scaling, the
          # gradient is 'loss_scale'. We divide by the batch size of 2 since the
          # loss is averaged across batch elements.
          expected_gradient = loss_scale / 2
          identity_with_grad_check_fn = (
              mp_test_util.create_identity_with_grad_check_fn(
                  expected_dtype=tf.float16,
                  expected_gradient=[expected_gradient]))
          y = core.Lambda(identity_with_grad_check_fn)(y)
        model = models.Model(inputs=x, outputs=y)

        def loss_fn(y_true, y_pred):
          del y_true
          return tf.reduce_mean(y_pred)

        opt = gradient_descent.SGD(learning_rate)
        if use_loss_scaling:
          opt = loss_scale_optimizer.LossScaleOptimizer(
              opt, dynamic=False, initial_scale=loss_scale)
        model.compile(
            opt,
            loss=loss_fn,
            run_eagerly=testing_utils.should_run_eagerly())

    x = np.ones((2, 1))
    y = np.ones((2, 1))
    dataset = tf.data.Dataset.from_tensor_slices((x, y)).batch(2)
    model.fit(dataset)
    for layer in (layer1, layer2, layer3, layer4):
      if layer.losses:
        # Layer has weight regularizer
        self.assertEqual(backend.eval(layer.v), 1 - 2 * learning_rate)
      else:
        # Layer does not have weight regularizer
        self.assertEqual(backend.eval(layer.v), 1 - learning_rate)

  @keras_parameterized.run_all_keras_modes(always_skip_v1=True)
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'pass_loss_scale_to_policy',
          'strategy_fn': create_mirrored_strategy,
          'pass_loss_scale_to_policy': True,
      }, {
          'testcase_name': 'get_config',
          'strategy_fn': create_mirrored_strategy,
          'get_config': True,
      }, {
          'testcase_name': 'get_config_v1_lso',
          'strategy_fn': create_mirrored_strategy,
          'get_config': True,
          'use_v1_loss_scale_optimizer': True,
      }, {
          'testcase_name': 'get_config_and_pass_loss_scale_to_policy',
          'strategy_fn': create_mirrored_strategy,
          'get_config': True,
          'pass_loss_scale_to_policy': True,
      })
  def test_dynamic_loss_scaling(self,
                                strategy_fn,
                                pass_loss_scale_to_policy=False,
                                get_config=False,
                                use_v1_loss_scale_optimizer=False):
    strategy = strategy_fn()
    initial_loss_scale = 2.
    batch_size = 4
    expected_gradient = backend.variable([initial_loss_scale / batch_size],
                                         dtype=tf.float16)
    # If this variable is set to True, the model below will have NaN gradients
    have_nan_gradients = backend.variable(False, dtype=tf.bool)
    with strategy.scope():
      opt = gradient_descent.SGD(1.)
      if pass_loss_scale_to_policy:
        loss_scale = tf.mixed_precision.experimental.DynamicLossScale(
            initial_loss_scale=initial_loss_scale, increment_period=2)
        p = policy.PolicyV1('mixed_float16', loss_scale=loss_scale)
      elif use_v1_loss_scale_optimizer:
        loss_scale = tf.mixed_precision.experimental.DynamicLossScale(
            initial_loss_scale=initial_loss_scale, increment_period=2)
        p = policy.Policy('mixed_float16')
        opt = loss_scale_optimizer.LossScaleOptimizerV1(
            opt, loss_scale)
      else:
        p = policy.Policy('mixed_float16')
        opt = loss_scale_optimizer.LossScaleOptimizer(
            opt, initial_scale=initial_loss_scale, dynamic_growth_steps=2)
      with policy.policy_scope(p):
        x = layers.Input(
            shape=(1,), batch_size=batch_size, dtype=tf.float16)
        layer = mp_test_util.MultiplyLayer(assert_type=tf.float16)
        y = layer(x)
        identity_with_nan_grads = (
            mp_test_util.create_identity_with_nan_gradients_fn(
                have_nan_gradients))
        y = core.Lambda(identity_with_nan_grads)(y)
        identity_with_grad_check_fn = (
            mp_test_util.create_identity_with_grad_check_fn(
                expected_dtype=tf.float16,
                expected_gradient=expected_gradient))
        y = core.Lambda(identity_with_grad_check_fn)(y)
        model = models.Model(inputs=x, outputs=y)
        if get_config:
          config = model.get_config()
          model = model.__class__.from_config(
              config,
              custom_objects={'MultiplyLayer': mp_test_util.MultiplyLayer})
          (layer,) = (layer for layer in model.layers
                      if isinstance(layer, mp_test_util.MultiplyLayer))

        def loss_fn(y_true, y_pred):
          del y_true
          return tf.reduce_mean(y_pred)

        model.compile(
            opt,
            loss=loss_fn,
            run_eagerly=testing_utils.should_run_eagerly())

    self.assertEqual(backend.eval(layer.v), 1)
    x = np.ones((batch_size, 1))
    y = np.ones((batch_size, 1))
    dataset = tf.data.Dataset.from_tensor_slices((x, y)).batch(batch_size)
    model.fit(dataset)
    # The variables starts with 1 and has a gradient of 1, so will go down by 1
    # each step.
    self.assertEqual(backend.eval(layer.v), 0)

    model.fit(dataset)
    self.assertEqual(backend.eval(layer.v), -1)

    # There have been two steps without NaNs, so the loss scale will double
    backend.set_value(expected_gradient,
                      backend.get_value(expected_gradient * 2))
    model.fit(dataset)
    self.assertEqual(backend.eval(layer.v), -2)

    # Next test with NaN gradients.
    backend.set_value(have_nan_gradients, True)
    model.fit(dataset)
    # Variable should not be updated
    self.assertEqual(backend.eval(layer.v), -2)

    # Test with finite gradients again
    backend.set_value(have_nan_gradients, False)
    # The loss scale will be halved due to the NaNs, so the gradient will also
    # be halved
    backend.set_value(expected_gradient,
                      backend.get_value(expected_gradient / 2))
    model.fit(dataset)
    self.assertEqual(backend.eval(layer.v), -3)

  @combinations.generate(combinations.combine(mode=['graph', 'eager']))
  def test_loss_scale_optimizer_overrides_policy_v1_loss_scale(self):
    with policy.policy_scope(policy.PolicyV1('float32', loss_scale=10.)):
      opt = gradient_descent.SGD(1.)
      opt = loss_scale_optimizer.LossScaleOptimizer(opt, dynamic=False,
                                                    initial_scale=5.)
      x = layers.Input(shape=(1,))
      y = mp_test_util.MultiplyLayer()(x)
      model = models.Model(x, y)
      model.compile(opt, loss='mse')
      self.assertEqual(self.evaluate(model.optimizer.loss_scale), 5.)

  @combinations.generate(combinations.combine(mode=['graph', 'eager']))
  def test_policy_v1_without_loss_scale(self):
    with policy.policy_scope(policy.PolicyV1('mixed_float16',
                                             loss_scale=None)):
      opt = gradient_descent.SGD(1.)
      x = layers.Input(shape=(1,))
      y = mp_test_util.MultiplyLayer()(x)
      model = models.Model(x, y)
      model.compile(opt, loss='mse')
      self.assertNotIsInstance(model.optimizer,
                               loss_scale_optimizer.LossScaleOptimizer)

  @combinations.generate(combinations.combine(mode=['graph', 'eager']))
  def test_pass_invalid_optimizer_with_loss_scaling(self):
    with policy.policy_scope(policy.PolicyV1('float32', loss_scale=10.)):
      x = layers.Input(shape=(1,))
      y = mp_test_util.MultiplyLayer()(x)
      model = models.Model(x, y)
      if tf.executing_eagerly():
        error_msg = 'Use a `tf.keras` Optimizer instead'
      else:
        error_msg = 'optimizer" must be an instance of '
      with self.assertRaisesRegex(ValueError, error_msg):
        model.compile(optimizer_v1.SGD(1.), 'mse')

  @combinations.generate(combinations.combine(mode=['graph', 'eager']))
  def test_functional_model_loss_dtype(self):
    with policy.policy_scope('float16'):
      x = layers.Input(shape=(1,))
      y = mp_test_util.MultiplyLayer()(x)
      model = models.Model(x, y)
      model.add_loss(tf.cast(y, 'float32'))
      # The loss should not be casted to the policy's dtype.
      self.assertEqual(model.losses[0].dtype, 'float32')

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn,
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'base_h5',
          'strategy_fn': default_strategy_fn,
          'h5': True,
      }, {
          'testcase_name': 'distribute_h5',
          'strategy_fn': create_mirrored_strategy,
          'h5': True,
      })
  def test_save_weights_with_autocast_vars(self, strategy_fn, h5=False):
    with strategy_fn().scope():
      with policy.policy_scope('mixed_float16'):
        x = layers.Input(shape=(1,), batch_size=2)
        layer = mp_test_util.MultiplyLayer(assert_type=tf.float16)
        y = layer(x)
        model = models.Model(inputs=x, outputs=y)

    model.set_weights([np.array(100.)])
    x = np.ones((2, 1))
    self.assertAllClose(backend.get_value(model(x)), x * 100.)
    suffix = '.h5' if h5 else ''
    weights_file = os.path.join(self.get_temp_dir(), 'weights' + suffix)
    model.save_weights(weights_file)

    model.set_weights([np.array(200.)])
    self.assertAllClose(backend.get_value(model(x)), x * 200.)
    model.load_weights(weights_file)
    self.assertAllClose(backend.get_value(model(x)), x * 100.)
    self.assertEqual(model.get_weights(), [np.array(100.)])

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn,
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'different_var_name',
          'strategy_fn': default_strategy_fn,
          'var_name': 'w'
      }, {
          'testcase_name': 'different_var_name_distribute',
          'strategy_fn': create_mirrored_strategy,
          'var_name': 'w'
      })
  def test_save_slot_variables_with_autocast_vars(self,
                                                  strategy_fn,
                                                  var_name='v'):
    p = policy.Policy('mixed_float16')
    with strategy_fn().scope(), policy.policy_scope(p):
      x = layers.Input(shape=(2,), batch_size=2)
      # Having a var_name other than 'v' tests that a fixed bug (b/134713714)
      # does not reoccur. The bug was that a crash would occur when saving a
      # checkpoint where an AutoCastVariable with a slot variable would have a
      # different name than the layer attribute's name (layer.v in this case).
      layer = mp_test_util.MultiplyLayer(assert_type=tf.float16,
                                         var_name=var_name)
      y = layer(x)
      model = models.Model(inputs=x, outputs=y)
      opt = gradient_descent.SGD(1., 1.)
      opt = loss_scale_optimizer.LossScaleOptimizer(opt, dynamic=False,
                                                    initial_scale=1)
      model.compile(
          optimizer=opt,
          loss='mse',
          run_eagerly=testing_utils.should_run_eagerly())

    model.fit(np.ones((2, 2)), np.zeros((2, 2)), batch_size=2)
    weights_file = os.path.join(self.get_temp_dir(), 'weights')
    model.save_weights(weights_file)
    saved_slot = backend.get_value(opt.get_slot(layer.v, 'momentum'))

    model.fit(np.ones((2, 2)), np.zeros((2, 2)), batch_size=2)
    new_slot = backend.get_value(opt.get_slot(layer.v, 'momentum'))
    self.assertNotEqual(new_slot, saved_slot)

    model.load_weights(weights_file)
    restored_slot = backend.get_value(opt.get_slot(layer.v, 'momentum'))
    self.assertEqual(restored_slot, saved_slot)

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(*TESTCASES)
  def test_save_weights_with_dynamic_loss_scaling(self, strategy_fn):
    strategy = strategy_fn()
    if (isinstance(strategy, tf.distribute.MirroredStrategy) and
        not tf.executing_eagerly()):
      # TODO(b/121381184): Enable running the test in this case.
      return

    # Create and run model.
    with strategy.scope():
      x = layers.Input(shape=(2,), batch_size=2, dtype=tf.float32)
      y = mp_test_util.MultiplyLayer(assert_type=tf.float32)(x)
      model = models.Model(inputs=x, outputs=y)

      opt = gradient_descent.SGD(1.)
      opt = loss_scale_optimizer.LossScaleOptimizer(
          opt, initial_scale=1., dynamic_growth_steps=2.)
      model.compile(
          optimizer=opt,
          loss='mse',
          run_eagerly=testing_utils.should_run_eagerly())
    # Run for 3 steps (6 examples with a batch size of 2)
    model.fit(np.zeros((6, 2)), np.zeros((6, 2)), batch_size=2)
    self.assertEqual(backend.get_value(opt.loss_scale), 2)
    self.assertEqual(backend.get_value(opt.dynamic_counter), 1)

    # Save model weights.
    save_prefix = os.path.join(self.get_temp_dir(), 'ckpt')
    model.save_weights(save_prefix)

    # Run model again for 1 step (2 examples with a batch size of 2)
    model.fit(np.zeros((2, 2)), np.zeros((2, 2)), batch_size=2)
    self.assertEqual(backend.get_value(opt.loss_scale), 4)
    self.assertEqual(backend.get_value(opt.dynamic_counter), 0)

    # Load model weights and ensure loss scale weights are restored.
    model.load_weights(save_prefix)
    self.assertEqual(backend.get_value(opt.loss_scale), 2)
    self.assertEqual(backend.get_value(opt.dynamic_counter), 1)

  @keras_parameterized.run_all_keras_modes
  def test_restore_old_loss_scale_checkpoint(self):
    # Ensure a checkpoint from TF 2.2 can be loaded. The checkpoint format
    # of LossScaleOptimizer changed, but old checkpoints can still be loaded
    opt = gradient_descent.SGD(0.1, momentum=0.1)
    opt = loss_scale_optimizer.LossScaleOptimizer(opt)
    model = sequential.Sequential([core.Dense(2,)])

    # The checkpoint and expected values were obtained from the program in
    # testdata/BUILD.
    ckpt_dir = os.path.join(
        flags.FLAGS['test_srcdir'].value,
        'org_keras/keras',
        'mixed_precision/testdata/lso_ckpt_tf2.2')
    # ckpt_dir = test.test_src_dir_path(
    #     'python/keras/mixed_precision/testdata/lso_ckpt_tf2.2')
    model.load_weights(os.path.join(ckpt_dir, 'ckpt'))
    model.compile(opt, 'mse', run_eagerly=testing_utils.should_run_eagerly())
    model(np.zeros((2, 2)))  # Create model weights
    opt._create_all_weights(model.weights)
    expected_kernel = np.array([[9.229685, 10.901115], [10.370763, 9.757362]])
    expected_slot = np.array([[10.049943, 9.917691], [10.049943, 9.917691]])
    self.assertAllClose(self.evaluate(model.weights[0]), expected_kernel)
    self.assertAllClose(
        self.evaluate(opt.get_slot(model.weights[0], 'momentum')),
        expected_slot)
    self.assertEqual(self.evaluate(opt.loss_scale), 32768)
    self.assertEqual(self.evaluate(opt.dynamic_counter), 1)

    # Check restoring works even after the model is compiled and the weights
    # have been created.
    model.fit(np.random.normal(size=(2, 2)), np.random.normal(size=(2, 2)))
    self.assertNotAllClose(self.evaluate(model.weights[0]), expected_kernel)
    self.assertNotAllClose(
        self.evaluate(opt.get_slot(model.weights[0], 'momentum')),
        expected_slot)
    model.load_weights(os.path.join(ckpt_dir, 'ckpt'))
    self.assertAllClose(self.evaluate(model.weights[0]), expected_kernel)
    self.assertAllClose(
        self.evaluate(opt.get_slot(model.weights[0], 'momentum')),
        expected_slot)
    self.assertEqual(self.evaluate(opt.loss_scale), 32768)
    self.assertEqual(self.evaluate(opt.dynamic_counter), 1)

  def test_restore_old_saved_model(self):
    saved_model_dir = os.path.join(
        flags.FLAGS['test_srcdir'].value,
        'org_keras/keras',
        'mixed_precision/testdata/lso_savedmodel_tf2.2')
    # saved_model_dir = test.test_src_dir_path(
    #     'python/keras/mixed_precision/testdata/'
    #     'lso_savedmodel_tf2.2')
    model = save.load_model(saved_model_dir)
    expected_kernel = np.array([[9.229685, 10.901115], [10.370763, 9.757362]])
    self.assertAllClose(backend.eval(model.weights[0]), expected_kernel)
    self.assertEqual(type(model.optimizer),
                     loss_scale_optimizer.LossScaleOptimizer)

  @keras_parameterized.run_all_keras_modes
  @parameterized.named_parameters(
      {
          'testcase_name': 'base',
          'strategy_fn': default_strategy_fn,
      }, {
          'testcase_name': 'distribute',
          'strategy_fn': create_mirrored_strategy,
      }, {
          'testcase_name': 'use_v1_lso',
          'strategy_fn': create_mirrored_strategy,
          'use_v1_loss_scale_optimizer': True
      }, {
          'testcase_name': 'base_h5',
          'strategy_fn': default_strategy_fn,
          'h5': True,
      }, {
          'testcase_name': 'distribute_h5',
          'strategy_fn': create_mirrored_strategy,
          'h5': True,
      })
  def test_save_model_with_dynamic_loss_scaling(
      self, strategy_fn, h5=False, use_v1_loss_scale_optimizer=False):
    # TODO(reedwm): Support and test saving model with a mixed_[b]float16 policy
    # as well.
    strategy = strategy_fn()
    if (isinstance(strategy, tf.distribute.MirroredStrategy) and
        not tf.executing_eagerly()):
      # TODO(b/121381184): Enable running the test in this case.
      return

    # Create and run model.
    with strategy.scope():
      x = layers.Input(shape=(2,), batch_size=2, dtype=tf.float32)
      y = mp_test_util.MultiplyLayer()(x)
      model = models.Model(inputs=x, outputs=y)

      opt = gradient_descent.SGD(1.)
      if use_v1_loss_scale_optimizer:
        loss_scale = tf.mixed_precision.experimental.DynamicLossScale(
            initial_loss_scale=1., increment_period=2.)
        opt = loss_scale_optimizer.LossScaleOptimizerV1(opt, loss_scale)
      else:
        opt = loss_scale_optimizer.LossScaleOptimizer(opt, initial_scale=1.,
                                                      dynamic_growth_steps=2.)
      model.compile(
          optimizer=opt,
          loss='mse',
          run_eagerly=testing_utils.should_run_eagerly())
    # Run for 3 steps (6 examples with a batch size of 2)
    model.fit(np.ones((6, 2)), np.zeros((6, 2)), batch_size=2)
    self.assertEqual(backend.get_value(opt.loss_scale), 2)
    self.assertEqual(backend.get_value(opt.dynamic_counter), 1)
    (weight,) = model.trainable_weights
    orig_weight = backend.get_value(weight)

    # Save model weights.
    save_path = os.path.join(self.get_temp_dir(), 'model')
    model.save(save_path, save_format='h5' if h5 else 'tf')

    # Run model again for 1 step (2 examples with a batch size of 2)
    model.fit(np.ones((2, 2)), np.zeros((2, 2)), batch_size=2)
    new_weight = backend.get_value(weight)
    self.assertNotEqual(new_weight, orig_weight)
    self.assertEqual(backend.get_value(opt.loss_scale), 4)
    self.assertEqual(backend.get_value(opt.dynamic_counter), 0)

    # Load model weights and ensure loss scale weights are restored.
    model = save.load_model(
        save_path, custom_objects={'MultiplyLayer': mp_test_util.MultiplyLayer})
    (weight,) = model.trainable_weights
    loaded_weight = backend.get_value(weight)
    self.assertEqual(loaded_weight, orig_weight)
    # Currently the loss scale isn't always saved when the model is saved with
    # Model.save(). So we assert the loss scale either has the value when it was
    # saved, or the value it was initialized with.
    # TODO(reedwm): Always save/restore the loss scale with Model.save().
    self.assertIn(backend.get_value(model.optimizer.loss_scale), (1, 2))
    self.assertIn(backend.get_value(model.optimizer.dynamic_counter), (0, 1))

    # Test optimizer attributes and type
    self.assertEqual(model.optimizer.initial_scale, 1.)
    self.assertEqual(model.optimizer.dynamic_growth_steps, 2.)
    self.assertEqual(type(model.optimizer),
                     loss_scale_optimizer.LossScaleOptimizer)


if __name__ == '__main__':
  base_layer_utils.enable_v2_dtype_behavior()
  tf.test.main()
