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Arguments:
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patience: Number of epochs to wait after min has been hit. After this
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number of no improvement, training stops.
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"""
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def __init__(self, patience=0):
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super(EarlyStoppingAtMinLoss, self).__init__()
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self.patience = patience
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# best_weights to store the weights at which the minimum loss occurs.
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self.best_weights = None
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def on_train_begin(self, logs=None):
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# The number of epoch it has waited when loss is no longer minimum.
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self.wait = 0
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# The epoch the training stops at.
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self.stopped_epoch = 0
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# Initialize the best as infinity.
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self.best = np.Inf
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def on_epoch_end(self, epoch, logs=None):
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current = logs.get("loss")
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if np.less(current, self.best):
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self.best = current
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self.wait = 0
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# Record the best weights if current results is better (less).
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self.best_weights = self.model.get_weights()
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else:
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self.wait += 1
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if self.wait >= self.patience:
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self.stopped_epoch = epoch
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self.model.stop_training = True
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print("Restoring model weights from the end of the best epoch.")
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self.model.set_weights(self.best_weights)
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def on_train_end(self, logs=None):
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if self.stopped_epoch > 0:
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print("Epoch %05d: early stopping" % (self.stopped_epoch + 1))
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model = get_model()
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model.fit(
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x_train,
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y_train,
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batch_size=64,
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steps_per_epoch=5,
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epochs=30,
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verbose=0,
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callbacks=[LossAndErrorPrintingCallback(), EarlyStoppingAtMinLoss()],
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)
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For batch 0, loss is 34.49.
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For batch 1, loss is 438.63.
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For batch 2, loss is 301.08.
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For batch 3, loss is 228.22.
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For batch 4, loss is 183.83.
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The average loss for epoch 0 is 183.83 and mean absolute error is 8.24.
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For batch 0, loss is 9.19.
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For batch 1, loss is 7.99.
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For batch 2, loss is 7.32.
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For batch 3, loss is 6.83.
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For batch 4, loss is 6.31.
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The average loss for epoch 1 is 6.31 and mean absolute error is 2.07.
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For batch 0, loss is 5.26.
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For batch 1, loss is 4.62.
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For batch 2, loss is 4.51.
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For batch 3, loss is 4.56.
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For batch 4, loss is 4.52.
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The average loss for epoch 2 is 4.52 and mean absolute error is 1.72.
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For batch 0, loss is 4.36.
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For batch 1, loss is 6.15.
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For batch 2, loss is 10.84.
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For batch 3, loss is 17.60.
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For batch 4, loss is 26.95.
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The average loss for epoch 3 is 26.95 and mean absolute error is 4.29.
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Restoring model weights from the end of the best epoch.
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Epoch 00004: early stopping
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<tensorflow.python.keras.callbacks.History at 0x15e0f08d0>
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Learning rate scheduling
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In this example, we show how a custom Callback can be used to dynamically change the learning rate of the optimizer during the course of training.
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See callbacks.LearningRateScheduler for a more general implementations.
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class CustomLearningRateScheduler(keras.callbacks.Callback):
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"""Learning rate scheduler which sets the learning rate according to schedule.
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Arguments:
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schedule: a function that takes an epoch index
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(integer, indexed from 0) and current learning rate
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as inputs and returns a new learning rate as output (float).
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"""
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def __init__(self, schedule):
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super(CustomLearningRateScheduler, self).__init__()
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self.schedule = schedule
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def on_epoch_begin(self, epoch, logs=None):
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if not hasattr(self.model.optimizer, "lr"):
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raise ValueError('Optimizer must have a "lr" attribute.')
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# Get the current learning rate from model's optimizer.
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lr = float(tf.keras.backend.get_value(self.model.optimizer.learning_rate))
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