522 lines
20 KiB
Python
522 lines
20 KiB
Python
# Copyright 2023 The TensorFlow Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ==============================================================================
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"""Library for exporting inference-only Keras models/layers."""
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import tensorflow.compat.v2 as tf
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from tensorflow.python.util.tf_export import keras_export
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from keras.engine import base_layer
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from keras.engine import functional
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from keras.engine import sequential
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from keras.utils import io_utils
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@keras_export("keras.export.ExportArchive")
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class ExportArchive(tf.__internal__.tracking.AutoTrackable):
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"""ExportArchive is used to write SavedModel artifacts (e.g. for inference).
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If you have a Keras model or layer that you want to export as SavedModel for
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serving (e.g. via TensorFlow-Serving), you can use `ExportArchive`
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to configure the different serving endpoints you need to make available,
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as well as their signatures. Simply instantiate an `ExportArchive`,
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use `track()` to register the layer(s) or model(s) to be used,
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then use the `add_endpoint()` method to register a new serving endpoint.
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When done, use the `write_out()` method to save the artifact.
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The resulting artifact is a SavedModel and can be reloaded via
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`tf.saved_model.load`.
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Examples:
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Here's how to export a model for inference.
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```python
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[tf.TensorSpec(shape=(None, 3), dtype=tf.float32)],
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)
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export_archive.write_out("path/to/location")
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# Elsewhere, we can reload the artifact and serve it.
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# The endpoint we added is available as a method:
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serving_model = tf.saved_model.load("path/to/location")
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outputs = serving_model.serve(inputs)
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```
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Here's how to export a model with one endpoint for inference and one
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endpoint for a training-mode forward pass (e.g. with dropout on).
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```python
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="call_inference",
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fn=lambda x: model.call(x, training=False),
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input_signature=[tf.TensorSpec(shape=(None, 3), dtype=tf.float32)],
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)
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export_archive.add_endpoint(
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name="call_training",
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fn=lambda x: model.call(x, training=True),
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input_signature=[tf.TensorSpec(shape=(None, 3), dtype=tf.float32)],
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)
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export_archive.write_out("path/to/location")
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```
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"""
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def __init__(self):
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self._endpoint_names = []
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self._endpoint_signatures = {}
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self._trackables = []
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self.tensorflow_version = tf.__version__
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def track(self, layer):
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"""Track the variables (and other resources) of a layer or model."""
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if not isinstance(layer, base_layer.Layer):
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raise ValueError(
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"Invalid layer type. Expected an instance of "
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"`keras.layers.Layer` or `keras.Model`. "
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f"Received instead an object of type '{type(layer)}'. "
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f"Object received: {layer}"
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)
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if not layer.built:
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raise ValueError(
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"The layer provided has not yet been built. "
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"It must be built before export."
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)
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self._trackables = list(layer._trackable_children().values())
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self.variables = list(layer.variables)
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self.trainable_variables = list(layer.trainable_variables)
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self.non_trainable_variables = list(layer.non_trainable_variables)
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def add_endpoint(self, name, fn, input_signature=None):
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"""Register a new serving endpoint.
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Arguments:
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name: Str, name of the endpoint.
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fn: A function. It should only leverage resources
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(e.g. `tf.Variable` objects or `tf.lookup.StaticHashTable`
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objects) that are available on the models/layers
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tracked by the `ExportArchive` (you can call `.track(model)`
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to track a new model).
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The shape and dtype of the inputs to the function must be
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known. For that purpose, you can either 1) make sure that
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`fn` is a `tf.function` that has been called at least once, or
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2) provide an `input_signature` argument that specifies the
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shape and dtype of the inputs (see below).
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input_signature: Used to specify the shape and dtype of the
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inputs to `fn`. List of `tf.TensorSpec` objects (one
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per positional input argument of `fn`). Nested arguments are
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allowed (see below for an example showing a Functional model
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with 2 input arguments).
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Example:
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Adding an endpoint using the `input_signature` argument when the
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model has a single input argument:
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```python
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[tf.TensorSpec(shape=(None, 3), dtype=tf.float32)],
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)
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```
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Adding an endpoint using the `input_signature` argument when the
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model has two positional input arguments:
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```python
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[
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tf.TensorSpec(shape=(None, 3), dtype=tf.float32),
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tf.TensorSpec(shape=(None, 4), dtype=tf.float32),
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],
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)
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```
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Adding an endpoint using the `input_signature` argument when the
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model has one input argument that is a list of 2 tensors (e.g.
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a Functional model with 2 inputs):
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```python
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model = keras.Model(inputs=[x1, x2], outputs=outputs)
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[
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[
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tf.TensorSpec(shape=(None, 3), dtype=tf.float32),
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tf.TensorSpec(shape=(None, 4), dtype=tf.float32),
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],
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],
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)
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```
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This also works with dictionary inputs:
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```python
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model = keras.Model(inputs={"x1": x1, "x2": x2}, outputs=outputs)
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[
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{
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"x1": tf.TensorSpec(shape=(None, 3), dtype=tf.float32),
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"x2": tf.TensorSpec(shape=(None, 4), dtype=tf.float32),
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},
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],
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)
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```
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Adding an endpoint that is a `tf.function`:
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```python
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@tf.function()
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def serving_fn(x):
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return model(x)
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# The function must be traced, i.e. it must be called at least once.
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serving_fn(tf.random.normal(shape=(2, 3)))
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export_archive = ExportArchive()
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export_archive.track(model)
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export_archive.add_endpoint(name="serve", fn=serving_fn)
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```
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"""
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if name in self._endpoint_names:
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raise ValueError(f"Endpoint name '{name}' is already taken.")
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if input_signature:
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decorated_fn = tf.function(fn, input_signature=input_signature)
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self._endpoint_signatures[name] = input_signature
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else:
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if isinstance(fn, tf.types.experimental.GenericFunction):
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if not fn._list_all_concrete_functions():
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raise ValueError(
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f"The provided tf.function '{fn}' "
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"has never been called. "
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"To specify the expected shape and dtype "
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"of the function's arguments, "
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"you must either provide a function that "
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"has been called at least once, or alternatively pass "
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"an `input_signature` argument in `add_endpoint()`."
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)
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decorated_fn = fn
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else:
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raise ValueError(
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"If the `fn` argument provided is not a `tf.function`, "
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"you must provide an `input_signature` argument to "
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"specify the shape and dtype of the function arguments. "
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"Example:\n\n"
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"export_archive.add_endpoint(\n"
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" name='call',\n"
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" fn=model.call,\n"
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" input_signature=[\n"
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" tf.TensorSpec(\n"
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" shape=(None, 224, 224, 3),\n"
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" dtype=tf.float32,\n"
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" )\n"
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" ],\n"
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")"
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)
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setattr(self, name, decorated_fn)
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self._endpoint_names.append(name)
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def add_variable_collection(self, name, variables):
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"""Register a set of variables to be retrieved after reloading.
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Arguments:
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name: The string name for the collection.
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variables: A tuple/list/set of `tf.Variable` instances.
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Example:
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```python
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export_archive = ExportArchive()
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export_archive.track(model)
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# Register an endpoint
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export_archive.add_endpoint(
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name="serve",
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fn=model.call,
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input_signature=[tf.TensorSpec(shape=(None, 3), dtype=tf.float32)],
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)
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# Save a variable collection
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export_archive.add_variable_collection(
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name="optimizer_variables", variables=model.optimizer.variables)
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export_archive.write_out("path/to/location")
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# Reload the object
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revived_object = tf.saved_model.load("path/to/location")
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# Retrieve the variables
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optimizer_variables = revived_object.optimizer_variables
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```
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"""
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if not isinstance(variables, (list, tuple, set)):
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raise ValueError(
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"Expected `variables` to be a list/tuple/set. "
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f"Received instead object of type '{type(variables)}'."
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)
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if not all(isinstance(v, tf.Variable) for v in variables):
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raise ValueError(
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"Expected all elements in `variables` to be "
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"`tf.Variable` instances. Found instead the following types: "
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f"{list(set(type(v) for v in variables))}"
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)
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setattr(self, name, list(variables))
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def write_out(self, filepath, options=None):
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"""Write the corresponding SavedModel to disk.
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Arguments:
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filepath: `str` or `pathlib.Path` object.
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Path where to save the artifact.
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options: `tf.saved_model.SaveOptions` object that specifies
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SavedModel saving options.
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**Note on TF-Serving**: all endpoints registered via `add_endpoint()`
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are made visible for TF-Serving in the SavedModel artifact. In addition,
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the first endpoint registered is made visible under the alias
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`"serving_default"` (unless an endpoint with the name
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`"serving_default"` was already registered manually),
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since TF-Serving requires this endpoint to be set.
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"""
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if not self._endpoint_names:
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raise ValueError(
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"No endpoints have been set yet. Call add_endpoint()."
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)
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if not self._trackables:
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raise ValueError("No assets are being tracked. Call track().")
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signatures = {}
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for name in self._endpoint_names:
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signatures[name] = self._get_concrete_fn(name)
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# Add "serving_default" signature key for TFServing
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if "serving_default" not in self._endpoint_names:
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signatures["serving_default"] = self._get_concrete_fn(
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self._endpoint_names[0]
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)
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tf.saved_model.save(
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self, filepath, options=options, signatures=signatures
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)
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# Print out available endpoints
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endpoints = "\n\n".join(
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_print_signature(getattr(self, name), name)
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for name in self._endpoint_names
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)
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io_utils.print_msg(
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f"Saved artifact at '{filepath}'. "
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"The following endpoints are available:\n\n"
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f"{endpoints}"
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)
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def _get_concrete_fn(self, endpoint):
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"""Workaround for some SavedModel quirks."""
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if endpoint in self._endpoint_signatures:
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return getattr(self, endpoint)
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else:
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traces = getattr(self, endpoint)._trackable_children("saved_model")
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return list(traces.values())[0]
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def export_model(model, filepath):
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export_archive = ExportArchive()
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export_archive.track(model)
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if isinstance(model, (functional.Functional, sequential.Sequential)):
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input_signature = tf.nest.map_structure(_make_tensor_spec, model.inputs)
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export_archive.add_endpoint("serve", model.__call__, input_signature)
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else:
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save_spec = model._get_save_spec()
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if not save_spec:
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raise ValueError(
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"The model provided has never called. "
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"It must be called at least once before export."
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)
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input_signature = [save_spec]
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export_archive.add_endpoint("serve", model.__call__, input_signature)
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export_archive.write_out(filepath)
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class ReloadedLayer(base_layer.Layer):
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"""Reload a Keras model/layer that was saved via SavedModel / ExportArchive.
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Arguments:
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filepath: `str` or `pathlib.Path` object. The path to the SavedModel.
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call_endpoint: Name of the endpoint to use as the `call()` method
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of the reloaded layer. If the SavedModel was created
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via `model.export()`,
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then the default endpoint name is `'serve'`. In other cases
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it may be named `'serving_default'`.
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Example:
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```python
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model.export("path/to/artifact")
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reloaded_layer = ReloadedLayer("path/to/artifact")
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outputs = reloaded_layer(inputs)
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```
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The reloaded object can be used like a regular Keras layer, and supports
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training/fine-tuning of its trainable weights. Note that the reloaded
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object retains none of the internal structure or custom methods of the
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original object -- it's a brand new layer created around the saved
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function.
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**Limitations:**
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* Only call endpoints with a single `inputs` tensor argument
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(which may optionally be a dict/tuple/list of tensors) are supported.
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For endpoints with multiple separate input tensor arguments, consider
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subclassing `ReloadedLayer` and implementing a `call()` method with a
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custom signature.
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* If you need training-time behavior to differ from inference-time behavior
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(i.e. if you need the reloaded object to support a `training=True` argument
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in `__call__()`), make sure that the training-time call function is
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saved as a standalone endpoint in the artifact, and provide its name
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to the `ReloadedLayer` via the `call_training_endpoint` argument.
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"""
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def __init__(
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self,
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filepath,
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call_endpoint="serve",
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call_training_endpoint=None,
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trainable=True,
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name=None,
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dtype=None,
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):
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# Initialize an empty layer, then add_weight() etc. as needed.
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super().__init__(trainable=trainable, name=name, dtype=dtype)
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self._reloaded_obj = tf.saved_model.load(filepath)
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self.filepath = filepath
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self.call_endpoint = call_endpoint
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self.call_training_endpoint = call_training_endpoint
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# Resolve the call function.
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if hasattr(self._reloaded_obj, call_endpoint):
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# Case 1: it's set as an attribute.
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self.call_endpoint_fn = getattr(self._reloaded_obj, call_endpoint)
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elif call_endpoint in self._reloaded_obj.signatures:
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# Case 2: it's listed in the `signatures` field.
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self.call_endpoint_fn = self._reloaded_obj.signatures[call_endpoint]
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else:
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raise ValueError(
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f"The endpoint '{call_endpoint}' is neither an "
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"attribute of the reloaded SavedModel, nor an entry "
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"in the `signatures` field of the reloaded SavedModel. "
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)
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# Resolving the training function.
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if call_training_endpoint:
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if hasattr(self._reloaded_obj, call_training_endpoint):
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self.call_training_endpoint_fn = getattr(
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self._reloaded_obj, call_training_endpoint
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)
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elif call_training_endpoint in self._reloaded_obj.signatures:
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self.call_training_endpoint_fn = self._reloaded_obj.signatures[
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call_training_endpoint
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]
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else:
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raise ValueError(
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f"The endpoint '{call_training_endpoint}' is "
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"neither an attribute of the reloaded SavedModel, "
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"nor an entry in the `signatures` field of "
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"the reloaded SavedModel. "
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)
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# Add trainable and non-trainable weights from the call_endpoint_fn.
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all_fns = [self.call_endpoint_fn]
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if call_training_endpoint:
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all_fns.append(self.call_training_endpoint_fn)
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trainable_variables_ids = set()
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non_trainable_variables_ids = set()
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for fn in all_fns:
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# The function may or may not be already a concrete function
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if hasattr(fn, "concrete_functions"):
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concrete_functions = fn.concrete_functions
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else:
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concrete_functions = [fn]
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for concrete_fn in concrete_functions:
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for v in concrete_fn.trainable_variables:
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if id(v) not in trainable_variables_ids:
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self._add_existing_weight(v, trainable=True)
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trainable_variables_ids.add(id(v))
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for v in concrete_fn.variables:
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if (
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id(v) not in trainable_variables_ids
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and id(v) not in non_trainable_variables_ids
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):
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self._add_existing_weight(v, trainable=False)
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non_trainable_variables_ids.add(id(v))
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self.built = True
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def _add_existing_weight(self, weight, trainable):
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"""Calls add_weight() to register but not create an existing weight."""
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self.add_weight(
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name=weight.name,
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shape=weight.shape,
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dtype=weight.dtype,
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trainable=trainable,
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getter=lambda *_, **__: weight,
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)
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def call(self, inputs, training=False, **kwargs):
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if training:
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if self.call_training_endpoint:
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return self.call_training_endpoint_fn(inputs, **kwargs)
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return self.call_endpoint_fn(inputs, **kwargs)
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def get_config(self):
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base_config = super().get_config()
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config = {
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# Note: this is not intended to be portable.
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"filepath": self.filepath,
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"call_endpoint": self.call_endpoint,
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"call_training_endpoint": self.call_training_endpoint,
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}
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return {**base_config, **config}
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|
|
|
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def _make_tensor_spec(x):
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return tf.TensorSpec(x.shape, dtype=x.dtype)
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|
|
|
|
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def _print_signature(fn, name):
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concrete_fn = fn._list_all_concrete_functions()[0]
|
|
pprinted_signature = concrete_fn.pretty_printed_signature(verbose=True)
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|
lines = pprinted_signature.split("\n")
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|
lines = [f"* Endpoint '{name}'"] + lines[1:]
|
|
endpoint = "\n".join(lines)
|
|
return endpoint
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