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outputs = layers.Dense(10, name="predictions")(x)
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model = keras.Model(inputs=inputs, outputs=outputs)
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model.compile(
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optimizer=keras.optimizers.RMSprop(learning_rate=1e-3),
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loss=keras.losses.SparseCategoricalCrossentropy(from_logits=True),
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)
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# The displayed loss will be much higher than before
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# due to the regularization component.
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model.fit(x_train, y_train, batch_size=64, epochs=1)
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782/782 [==============================] - 1s 828us/step - loss: 3.5361
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<tensorflow.python.keras.callbacks.History at 0x14d6de210>
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You can do the same for logging metric values, using add_metric():
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class MetricLoggingLayer(layers.Layer):
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def call(self, inputs):
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# The `aggregation` argument defines
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# how to aggregate the per-batch values
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# over each epoch:
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# in this case we simply average them.
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self.add_metric(
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keras.backend.std(inputs), name="std_of_activation", aggregation="mean"
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)
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return inputs # Pass-through layer.
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inputs = keras.Input(shape=(784,), name="digits")
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x = layers.Dense(64, activation="relu", name="dense_1")(inputs)
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# Insert std logging as a layer.
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x = MetricLoggingLayer()(x)
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x = layers.Dense(64, activation="relu", name="dense_2")(x)
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outputs = layers.Dense(10, name="predictions")(x)
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model = keras.Model(inputs=inputs, outputs=outputs)
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model.compile(
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optimizer=keras.optimizers.RMSprop(learning_rate=1e-3),
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loss=keras.losses.SparseCategoricalCrossentropy(from_logits=True),
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)
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model.fit(x_train, y_train, batch_size=64, epochs=1)
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782/782 [==============================] - 1s 859us/step - loss: 0.5469 - std_of_activation: 0.9414
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<tensorflow.python.keras.callbacks.History at 0x14d827ed0>
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In the Functional API, you can also call model.add_loss(loss_tensor), or model.add_metric(metric_tensor, name, aggregation).
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Here's a simple example:
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inputs = keras.Input(shape=(784,), name="digits")
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x1 = layers.Dense(64, activation="relu", name="dense_1")(inputs)
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x2 = layers.Dense(64, activation="relu", name="dense_2")(x1)
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outputs = layers.Dense(10, name="predictions")(x2)
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model = keras.Model(inputs=inputs, outputs=outputs)
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model.add_loss(tf.reduce_sum(x1) * 0.1)
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model.add_metric(keras.backend.std(x1), name="std_of_activation", aggregation="mean")
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model.compile(
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optimizer=keras.optimizers.RMSprop(1e-3),
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loss=keras.losses.SparseCategoricalCrossentropy(from_logits=True),
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)
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model.fit(x_train, y_train, batch_size=64, epochs=1)
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782/782 [==============================] - 1s 875us/step - loss: 3.4905 - std_of_activation: 0.0019
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<tensorflow.python.keras.callbacks.History at 0x14d944790>
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Note that when you pass losses via add_loss(), it becomes possible to call compile() without a loss function, since the model already has a loss to minimize.
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Consider the following LogisticEndpoint layer: it takes as inputs targets & logits, and it tracks a crossentropy loss via add_loss(). It also tracks classification accuracy via add_metric().
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class LogisticEndpoint(keras.layers.Layer):
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def __init__(self, name=None):
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super(LogisticEndpoint, self).__init__(name=name)
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self.loss_fn = keras.losses.BinaryCrossentropy(from_logits=True)
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self.accuracy_fn = keras.metrics.BinaryAccuracy()
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def call(self, targets, logits, sample_weights=None):
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# Compute the training-time loss value and add it
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# to the layer using `self.add_loss()`.
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loss = self.loss_fn(targets, logits, sample_weights)
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self.add_loss(loss)
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# Log accuracy as a metric and add it
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# to the layer using `self.add_metric()`.
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acc = self.accuracy_fn(targets, logits, sample_weights)
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self.add_metric(acc, name="accuracy")
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# Return the inference-time prediction tensor (for `.predict()`).
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return tf.nn.softmax(logits)
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You can use it in a model with two inputs (input data & targets), compiled without a loss argument, like this:
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import numpy as np
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inputs = keras.Input(shape=(3,), name="inputs")
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targets = keras.Input(shape=(10,), name="targets")
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logits = keras.layers.Dense(10)(inputs)
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predictions = LogisticEndpoint(name="predictions")(logits, targets)
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