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