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# Call model on inputs to create the variables of the dense layer.
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_ = model(tf.ones((1, 784)))
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# Create a Checkpoint with the same structure as before, and load the weights.
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tf.train.Checkpoint(
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dense=model.first_dense, kernel=model.kernel, bias=model.bias
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).restore(ckpt_path).assert_consumed()
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<tensorflow.python.training.tracking.util.CheckpointLoadStatus at 0x151ed1110>
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HDF5 format
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The HDF5 format contains weights grouped by layer names. The weights are lists ordered by concatenating the list of trainable weights to the list of non-trainable weights (same as layer.weights). Thus, a model can use a hdf5 checkpoint if it has the same layers and trainable statuses as saved in the checkpoint.
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Example:
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# Runnable example
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sequential_model = keras.Sequential(
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[
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keras.Input(shape=(784,), name="digits"),
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keras.layers.Dense(64, activation="relu", name="dense_1"),
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keras.layers.Dense(64, activation="relu", name="dense_2"),
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keras.layers.Dense(10, name="predictions"),
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]
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)
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sequential_model.save_weights("weights.h5")
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sequential_model.load_weights("weights.h5")
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Note that changing layer.trainable may result in a different layer.weights ordering when the model contains nested layers.
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class NestedDenseLayer(keras.layers.Layer):
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def __init__(self, units, name=None):
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super(NestedDenseLayer, self).__init__(name=name)
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self.dense_1 = keras.layers.Dense(units, name="dense_1")
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self.dense_2 = keras.layers.Dense(units, name="dense_2")
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def call(self, inputs):
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return self.dense_2(self.dense_1(inputs))
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nested_model = keras.Sequential([keras.Input((784,)), NestedDenseLayer(10, "nested")])
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variable_names = [v.name for v in nested_model.weights]
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print("variables: {}".format(variable_names))
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print("\nChanging trainable status of one of the nested layers...")
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nested_model.get_layer("nested").dense_1.trainable = False
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variable_names_2 = [v.name for v in nested_model.weights]
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print("\nvariables: {}".format(variable_names_2))
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print("variable ordering changed:", variable_names != variable_names_2)
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variables: ['nested/dense_1/kernel:0', 'nested/dense_1/bias:0', 'nested/dense_2/kernel:0', 'nested/dense_2/bias:0']
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Changing trainable status of one of the nested layers...
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variables: ['nested/dense_2/kernel:0', 'nested/dense_2/bias:0', 'nested/dense_1/kernel:0', 'nested/dense_1/bias:0']
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variable ordering changed: True
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Transfer learning example
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When loading pretrained weights from HDF5, it is recommended to load the weights into the original checkpointed model, and then extract the desired weights/layers into a new model.
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Example:
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def create_functional_model():
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inputs = keras.Input(shape=(784,), name="digits")
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x = keras.layers.Dense(64, activation="relu", name="dense_1")(inputs)
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x = keras.layers.Dense(64, activation="relu", name="dense_2")(x)
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outputs = keras.layers.Dense(10, name="predictions")(x)
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return keras.Model(inputs=inputs, outputs=outputs, name="3_layer_mlp")
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functional_model = create_functional_model()
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functional_model.save_weights("pretrained_weights.h5")
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# In a separate program:
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pretrained_model = create_functional_model()
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pretrained_model.load_weights("pretrained_weights.h5")
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# Create a new model by extracting layers from the original model:
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extracted_layers = pretrained_model.layers[:-1]
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extracted_layers.append(keras.layers.Dense(5, name="dense_3"))
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model = keras.Sequential(extracted_layers)
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model.summary()
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Model: "sequential_6"
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_________________________________________________________________
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Layer (type) Output Shape Param #
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=================================================================
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dense_1 (Dense) (None, 64) 50240
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_________________________________________________________________
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dense_2 (Dense) (None, 64) 4160
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_________________________________________________________________
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dense_3 (Dense) (None, 5) 325
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=================================================================
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Total params: 54,725
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Trainable params: 54,725
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Non-trainable params: 0
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_________________________________________________________________
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