def _clone_model(model, input_tensors):
"""Clone model with configs, except of weights."""
new_input_layers = {} # Cache for created layers.
# pylint: disable=protected-access
if input_tensors is not None:
# Make sure that all input tensors come from a Keras layer.
input_tensors = tf.nest.flatten(input_tensors)
for i, input_tensor in enumerate(input_tensors):
if not tf.keras.backend.is_keras_tensor(input_tensor):
raise ValueError('Expected keras tensor but get', input_tensor)
original_input_layer = model._input_layers[i]
newly_created_input_layer = input_tensor._keras_history.layer
new_input_layers[original_input_layer] = newly_created_input_layer
model_config, created_layers = models_utils._clone_layers_and_model_config(
model, new_input_layers, models_utils._clone_layer)
# pylint: enable=protected-access
# Reconstruct model from the config, using the cloned layers.
input_tensors, output_tensors, created_layers = (
functional.reconstruct_from_config(model_config,
created_layers=created_layers))
new_model = tf.keras.Model(input_tensors, output_tensors, name=model.name)
return new_model
def _clone_functional_model(model, input_tensors=None, layer_fn=_clone_layer):
"""Clone a functional `Model` instance.
Model cloning is similar to calling a model on new inputs,
except that it creates new layers (and thus new weights) instead
of sharing the weights of the existing layers.
Input layers are always cloned.
Args:
model: Instance of `Model`.
input_tensors: optional list of input tensors
to build the model upon. If not provided,
placeholders will be created.
layer_fn: callable to be applied on non-input layers in the model. By
default it clones the layer. Another example is to preserve the layer
to share the weights. This is required when we create a per-replica
copy of the model with distribution strategy; we want the weights to
be shared but still feed inputs separately so we create new input
layers.
Returns:
An instance of `Model` reproducing the behavior
of the original model, on top of new inputs tensors,
using newly instantiated weights.
Raises:
ValueError: in case of invalid `model` argument value or `layer_fn`
argument value.
"""
if not isinstance(model, Model):
raise ValueError(
'Expected `model` argument '
'to be a `Model` instance, got ', model)
if isinstance(model, Sequential):
raise ValueError(
'Expected `model` argument '
'to be a functional `Model` instance, '
'got a `Sequential` instance instead:', model)
if not model._is_graph_network:
raise ValueError('Expected `model` argument '
'to be a functional `Model` instance, '
'but got a subclass model instead.')
new_input_layers = {} # Cache for created layers.
if input_tensors is not None:
# Make sure that all input tensors come from a Keras layer.
input_tensors = tf.nest.flatten(input_tensors)
for i, input_tensor in enumerate(input_tensors):
original_input_layer = model._input_layers[i]
# Cache input layer. Create a new layer if the tensor is originally not
# from a Keras layer.
if not backend.is_keras_tensor(input_tensor):
name = original_input_layer.name
input_tensor = Input(tensor=input_tensor,
name='input_wrapper_for_' + name)
newly_created_input_layer = input_tensor._keras_history.layer
new_input_layers[
original_input_layer] = newly_created_input_layer
else:
new_input_layers[original_input_layer] = original_input_layer
if not callable(layer_fn):
raise ValueError('Expected `layer_fn` argument to be a callable.')
model_configs, created_layers = _clone_layers_and_model_config(
model, new_input_layers, layer_fn)
# Reconstruct model from the config, using the cloned layers.
input_tensors, output_tensors, created_layers = (
functional.reconstruct_from_config(model_configs,
created_layers=created_layers))
metrics_names = model.metrics_names
model = Model(input_tensors, output_tensors, name=model.name)
# Layers not directly tied to outputs of the Model, such as loss layers
# created in `add_loss` and `add_metric`.
ancillary_layers = [
layer for layer in created_layers.values() if layer not in model.layers
]
# TODO(b/162887610): This may need to adjust the inbound node index if the
# created layers had already been used to define other models.
if ancillary_layers:
new_nodes = tf.nest.flatten([
layer.inbound_nodes[1:] if
functional._should_skip_first_node(layer) else layer.inbound_nodes
for layer in created_layers.values()
])
_insert_ancillary_layers(model, ancillary_layers, metrics_names,
new_nodes)
return model