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Tanıtım
Geri arama, eğitim, değerlendirme veya çıkarım sırasında Keras modelinin davranışını özelleştirmek için güçlü bir araçtır. Örnekler arasında tf.keras.callbacks.TensorBoard
eğitim ilerleme ve sonuçları TensorBoard ile veya görselleştirmek için tf.keras.callbacks.ModelCheckpoint
eğitim sırasında modeliniz tasarruf periyodik etmek.
Bu kılavuzda, bir Keras geri aramasının ne olduğunu, ne yapabileceğini ve kendinizinkini nasıl oluşturabileceğinizi öğreneceksiniz. Başlamanız için birkaç basit geri arama uygulaması demosu sunuyoruz.
Kurmak
import tensorflow as tf
from tensorflow import keras
Keras geri aramalarına genel bakış
Tüm geri aramaları alt sınıfı keras.callbacks.Callback
sınıfını ve eğitim çeşitli aşamalarında, test ve tahmin etmede denilen yöntemler kümesi geçersiz kılar. Geri aramalar, eğitim sırasında modelin dahili durumları ve istatistikleri hakkında bir görünüm elde etmek için yararlıdır.
Sen (anahtar kelime argüman olarak geri aramaları listesini iletebilirsiniz callbacks
aşağıdaki modeli yöntemlerine):
Geri arama yöntemlerine genel bakış
genel yöntemler
on_(train|test|predict)_begin(self, logs=None)
Başında Aranan fit
/ evaluate
/ predict
.
on_(train|test|predict)_end(self, logs=None)
Sonunda denilen fit
/ evaluate
/ predict
.
Eğitim/test/tahmin için toplu düzeyde yöntemler
on_(train|test|predict)_batch_begin(self, batch, logs=None)
Eğitim/test/tahmin sırasında bir toplu işlenmeden hemen önce çağrılır.
on_(train|test|predict)_batch_end(self, batch, logs=None)
Eğitim/test/grup tahmininin sonunda çağrılır. Bu yöntem içinde, logs
ölçümlerini sonuçlarını içeren dict olup.
Dönem düzeyinde yöntemler (yalnızca eğitim)
on_epoch_begin(self, epoch, logs=None)
Eğitim sırasında bir çağın başlangıcında çağrılır.
on_epoch_end(self, epoch, logs=None)
Eğitim sırasında bir çağın sonunda çağrılır.
Temel bir örnek
Somut bir örneğe bakalım. Başlamak için tensorflow'u içe aktaralım ve basit bir Sıralı Keras modeli tanımlayalım:
# Define the Keras model to add callbacks to
def get_model():
model = keras.Sequential()
model.add(keras.layers.Dense(1, input_dim=784))
model.compile(
optimizer=keras.optimizers.RMSprop(learning_rate=0.1),
loss="mean_squared_error",
metrics=["mean_absolute_error"],
)
return model
Ardından, eğitim ve test için MNIST verilerini Keras veri kümeleri API'sinden yükleyin:
# Load example MNIST data and pre-process it
(x_train, y_train), (x_test, y_test) = tf.keras.datasets.mnist.load_data()
x_train = x_train.reshape(-1, 784).astype("float32") / 255.0
x_test = x_test.reshape(-1, 784).astype("float32") / 255.0
# Limit the data to 1000 samples
x_train = x_train[:1000]
y_train = y_train[:1000]
x_test = x_test[:1000]
y_test = y_test[:1000]
Şimdi, günlüğe kaydeden basit bir özel geri arama tanımlayın:
- Ne zaman
fit
/evaluate
/predict
başlar ve biter - Her dönem başladığında ve bittiğinde
- Her eğitim grubu başladığında ve bittiğinde
- Her değerlendirme (test) grubu başladığında ve bittiğinde
- Her bir çıkarım (tahmin) grubu başladığında ve bittiğinde
class CustomCallback(keras.callbacks.Callback):
def on_train_begin(self, logs=None):
keys = list(logs.keys())
print("Starting training; got log keys: {}".format(keys))
def on_train_end(self, logs=None):
keys = list(logs.keys())
print("Stop training; got log keys: {}".format(keys))
def on_epoch_begin(self, epoch, logs=None):
keys = list(logs.keys())
print("Start epoch {} of training; got log keys: {}".format(epoch, keys))
def on_epoch_end(self, epoch, logs=None):
keys = list(logs.keys())
print("End epoch {} of training; got log keys: {}".format(epoch, keys))
def on_test_begin(self, logs=None):
keys = list(logs.keys())
print("Start testing; got log keys: {}".format(keys))
def on_test_end(self, logs=None):
keys = list(logs.keys())
print("Stop testing; got log keys: {}".format(keys))
def on_predict_begin(self, logs=None):
keys = list(logs.keys())
print("Start predicting; got log keys: {}".format(keys))
def on_predict_end(self, logs=None):
keys = list(logs.keys())
print("Stop predicting; got log keys: {}".format(keys))
def on_train_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Training: start of batch {}; got log keys: {}".format(batch, keys))
def on_train_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Training: end of batch {}; got log keys: {}".format(batch, keys))
def on_test_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Evaluating: start of batch {}; got log keys: {}".format(batch, keys))
def on_test_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Evaluating: end of batch {}; got log keys: {}".format(batch, keys))
def on_predict_batch_begin(self, batch, logs=None):
keys = list(logs.keys())
print("...Predicting: start of batch {}; got log keys: {}".format(batch, keys))
def on_predict_batch_end(self, batch, logs=None):
keys = list(logs.keys())
print("...Predicting: end of batch {}; got log keys: {}".format(batch, keys))
Deneyelim:
model = get_model()
model.fit(
x_train,
y_train,
batch_size=128,
epochs=1,
verbose=0,
validation_split=0.5,
callbacks=[CustomCallback()],
)
res = model.evaluate(
x_test, y_test, batch_size=128, verbose=0, callbacks=[CustomCallback()]
)
res = model.predict(x_test, batch_size=128, callbacks=[CustomCallback()])
Starting training; got log keys: [] Start epoch 0 of training; got log keys: [] ...Training: start of batch 0; got log keys: [] ...Training: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 1; got log keys: [] ...Training: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 2; got log keys: [] ...Training: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Training: start of batch 3; got log keys: [] ...Training: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] Start testing; got log keys: [] ...Evaluating: start of batch 0; got log keys: [] ...Evaluating: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 1; got log keys: [] ...Evaluating: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 2; got log keys: [] ...Evaluating: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 3; got log keys: [] ...Evaluating: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] Stop testing; got log keys: ['loss', 'mean_absolute_error'] End epoch 0 of training; got log keys: ['loss', 'mean_absolute_error', 'val_loss', 'val_mean_absolute_error'] Stop training; got log keys: ['loss', 'mean_absolute_error', 'val_loss', 'val_mean_absolute_error'] Start testing; got log keys: [] ...Evaluating: start of batch 0; got log keys: [] ...Evaluating: end of batch 0; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 1; got log keys: [] ...Evaluating: end of batch 1; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 2; got log keys: [] ...Evaluating: end of batch 2; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 3; got log keys: [] ...Evaluating: end of batch 3; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 4; got log keys: [] ...Evaluating: end of batch 4; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 5; got log keys: [] ...Evaluating: end of batch 5; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 6; got log keys: [] ...Evaluating: end of batch 6; got log keys: ['loss', 'mean_absolute_error'] ...Evaluating: start of batch 7; got log keys: [] ...Evaluating: end of batch 7; got log keys: ['loss', 'mean_absolute_error'] Stop testing; got log keys: ['loss', 'mean_absolute_error'] Start predicting; got log keys: [] ...Predicting: start of batch 0; got log keys: [] ...Predicting: end of batch 0; got log keys: ['outputs'] ...Predicting: start of batch 1; got log keys: [] ...Predicting: end of batch 1; got log keys: ['outputs'] ...Predicting: start of batch 2; got log keys: [] ...Predicting: end of batch 2; got log keys: ['outputs'] ...Predicting: start of batch 3; got log keys: [] ...Predicting: end of batch 3; got log keys: ['outputs'] ...Predicting: start of batch 4; got log keys: [] ...Predicting: end of batch 4; got log keys: ['outputs'] ...Predicting: start of batch 5; got log keys: [] ...Predicting: end of batch 5; got log keys: ['outputs'] ...Predicting: start of batch 6; got log keys: [] ...Predicting: end of batch 6; got log keys: ['outputs'] ...Predicting: start of batch 7; got log keys: [] ...Predicting: end of batch 7; got log keys: ['outputs'] Stop predicting; got log keys: []
Kullanımı logs
dict
logs
dict kaybı değerinin ve bir yığın ya da dönemin sonunda tüm ölçümleri içerir. Örnek, kayıp ve ortalama mutlak hatayı içerir.
class LossAndErrorPrintingCallback(keras.callbacks.Callback):
def on_train_batch_end(self, batch, logs=None):
print(
"Up to batch {}, the average loss is {:7.2f}.".format(batch, logs["loss"])
)
def on_test_batch_end(self, batch, logs=None):
print(
"Up to batch {}, the average loss is {:7.2f}.".format(batch, logs["loss"])
)
def on_epoch_end(self, epoch, logs=None):
print(
"The average loss for epoch {} is {:7.2f} "
"and mean absolute error is {:7.2f}.".format(
epoch, logs["loss"], logs["mean_absolute_error"]
)
)
model = get_model()
model.fit(
x_train,
y_train,
batch_size=128,
epochs=2,
verbose=0,
callbacks=[LossAndErrorPrintingCallback()],
)
res = model.evaluate(
x_test,
y_test,
batch_size=128,
verbose=0,
callbacks=[LossAndErrorPrintingCallback()],
)
Up to batch 0, the average loss is 30.79. Up to batch 1, the average loss is 459.11. Up to batch 2, the average loss is 314.68. Up to batch 3, the average loss is 237.97. Up to batch 4, the average loss is 191.76. Up to batch 5, the average loss is 160.95. Up to batch 6, the average loss is 138.74. Up to batch 7, the average loss is 124.85. The average loss for epoch 0 is 124.85 and mean absolute error is 6.00. Up to batch 0, the average loss is 5.13. Up to batch 1, the average loss is 4.66. Up to batch 2, the average loss is 4.71. Up to batch 3, the average loss is 4.66. Up to batch 4, the average loss is 4.69. Up to batch 5, the average loss is 4.56. Up to batch 6, the average loss is 4.77. Up to batch 7, the average loss is 4.77. The average loss for epoch 1 is 4.77 and mean absolute error is 1.75. Up to batch 0, the average loss is 5.73. Up to batch 1, the average loss is 5.04. Up to batch 2, the average loss is 5.10. Up to batch 3, the average loss is 5.14. Up to batch 4, the average loss is 5.37. Up to batch 5, the average loss is 5.24. Up to batch 6, the average loss is 5.22. Up to batch 7, the average loss is 5.16.
Kullanımı self.model
özniteliği
: Onların yöntemlerden biri çağrıldığında günlük bilgilerini aldıktan ek olarak, geri aramaları eğitim / değerlendirme / çıkarımın şimdiki haliyle ilişkili modele erişimi self.model
.
Burada yapabileceğiniz şeylerden kaç vardır self.model
bir geri aramasında:
- Set
self.model.stop_training = True
derhal kesme eğitime. - (Şekilde mevcut en iyi duruma ait Mutate hyperparameters
self.model.optimizer
gibi),self.model.optimizer.learning_rate
. - Modeli dönemsel aralıklarla kaydedin.
- Çıktısını kaydedin
model.predict()
eğitimi sırasında bir sağlamlık denetimi olarak kullanmak, her dönemin sonunda birkaç test numunelerinin üzerinde. - Modelin zaman içinde ne öğrendiğini izlemek için her dönemin sonunda ara özelliklerin görselleştirmelerini çıkarın.
- vb.
Bunu birkaç örnekte çalışırken görelim.
Keras geri arama uygulamalarına örnekler
Minimum kayıpta erken durdurma
Bu ilk örnek gösterileri yaratılması Callback
kaybının asgari nitelik ayarlayarak, ulaşıldığında eğitim durur self.model.stop_training
(boolean). İsteğe bağlı olarak, bir argüman sağlayabilir patience
yerel bir minimum değere ulaşana sonra durdurmadan önce beklemesi gerektiğini kaç dönemini belirtmek için.
tf.keras.callbacks.EarlyStopping
daha eksiksiz ve genel uygulamasını sağlar.
import numpy as np
class EarlyStoppingAtMinLoss(keras.callbacks.Callback):
"""Stop training when the loss is at its min, i.e. the loss stops decreasing.
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()],
)
Up to batch 0, the average loss is 34.62. Up to batch 1, the average loss is 405.62. Up to batch 2, the average loss is 282.27. Up to batch 3, the average loss is 215.95. Up to batch 4, the average loss is 175.32. The average loss for epoch 0 is 175.32 and mean absolute error is 8.59. Up to batch 0, the average loss is 8.86. Up to batch 1, the average loss is 7.31. Up to batch 2, the average loss is 6.51. Up to batch 3, the average loss is 6.71. Up to batch 4, the average loss is 6.24. The average loss for epoch 1 is 6.24 and mean absolute error is 2.06. Up to batch 0, the average loss is 4.83. Up to batch 1, the average loss is 5.05. Up to batch 2, the average loss is 4.71. Up to batch 3, the average loss is 4.41. Up to batch 4, the average loss is 4.48. The average loss for epoch 2 is 4.48 and mean absolute error is 1.68. Up to batch 0, the average loss is 5.84. Up to batch 1, the average loss is 5.73. Up to batch 2, the average loss is 7.24. Up to batch 3, the average loss is 10.34. Up to batch 4, the average loss is 15.53. The average loss for epoch 3 is 15.53 and mean absolute error is 3.20. Restoring model weights from the end of the best epoch. Epoch 00004: early stopping <keras.callbacks.History at 0x7fd0843bf510>
Öğrenme hızı planlaması
Bu örnekte, eğitim sırasında optimize edicinin öğrenme oranını dinamik olarak değiştirmek için özel bir Geri Aramanın nasıl kullanılabileceğini gösteriyoruz.
Bkz callbacks.LearningRateScheduler
daha genel uygulamalar için.
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))
# Call schedule function to get the scheduled learning rate.
scheduled_lr = self.schedule(epoch, lr)
# Set the value back to the optimizer before this epoch starts
tf.keras.backend.set_value(self.model.optimizer.lr, scheduled_lr)
print("\nEpoch %05d: Learning rate is %6.4f." % (epoch, scheduled_lr))
LR_SCHEDULE = [
# (epoch to start, learning rate) tuples
(3, 0.05),
(6, 0.01),
(9, 0.005),
(12, 0.001),
]
def lr_schedule(epoch, lr):
"""Helper function to retrieve the scheduled learning rate based on epoch."""
if epoch < LR_SCHEDULE[0][0] or epoch > LR_SCHEDULE[-1][0]:
return lr
for i in range(len(LR_SCHEDULE)):
if epoch == LR_SCHEDULE[i][0]:
return LR_SCHEDULE[i][1]
return lr
model = get_model()
model.fit(
x_train,
y_train,
batch_size=64,
steps_per_epoch=5,
epochs=15,
verbose=0,
callbacks=[
LossAndErrorPrintingCallback(),
CustomLearningRateScheduler(lr_schedule),
],
)
Epoch 00000: Learning rate is 0.1000. Up to batch 0, the average loss is 26.55. Up to batch 1, the average loss is 435.15. Up to batch 2, the average loss is 298.00. Up to batch 3, the average loss is 225.91. Up to batch 4, the average loss is 182.66. The average loss for epoch 0 is 182.66 and mean absolute error is 8.16. Epoch 00001: Learning rate is 0.1000. Up to batch 0, the average loss is 7.30. Up to batch 1, the average loss is 6.22. Up to batch 2, the average loss is 6.76. Up to batch 3, the average loss is 6.37. Up to batch 4, the average loss is 5.98. The average loss for epoch 1 is 5.98 and mean absolute error is 2.01. Epoch 00002: Learning rate is 0.1000. Up to batch 0, the average loss is 4.23. Up to batch 1, the average loss is 4.56. Up to batch 2, the average loss is 4.81. Up to batch 3, the average loss is 4.63. Up to batch 4, the average loss is 4.67. The average loss for epoch 2 is 4.67 and mean absolute error is 1.73. Epoch 00003: Learning rate is 0.0500. Up to batch 0, the average loss is 6.24. Up to batch 1, the average loss is 5.62. Up to batch 2, the average loss is 5.48. Up to batch 3, the average loss is 5.09. Up to batch 4, the average loss is 4.68. The average loss for epoch 3 is 4.68 and mean absolute error is 1.77. Epoch 00004: Learning rate is 0.0500. Up to batch 0, the average loss is 3.38. Up to batch 1, the average loss is 3.83. Up to batch 2, the average loss is 3.53. Up to batch 3, the average loss is 3.64. Up to batch 4, the average loss is 3.76. The average loss for epoch 4 is 3.76 and mean absolute error is 1.54. Epoch 00005: Learning rate is 0.0500. Up to batch 0, the average loss is 3.62. Up to batch 1, the average loss is 3.79. Up to batch 2, the average loss is 3.75. Up to batch 3, the average loss is 3.83. Up to batch 4, the average loss is 4.37. The average loss for epoch 5 is 4.37 and mean absolute error is 1.65. Epoch 00006: Learning rate is 0.0100. Up to batch 0, the average loss is 6.73. Up to batch 1, the average loss is 6.13. Up to batch 2, the average loss is 5.11. Up to batch 3, the average loss is 4.57. Up to batch 4, the average loss is 4.21. The average loss for epoch 6 is 4.21 and mean absolute error is 1.61. Epoch 00007: Learning rate is 0.0100. Up to batch 0, the average loss is 3.37. Up to batch 1, the average loss is 3.83. Up to batch 2, the average loss is 3.80. Up to batch 3, the average loss is 3.50. Up to batch 4, the average loss is 3.31. The average loss for epoch 7 is 3.31 and mean absolute error is 1.42. Epoch 00008: Learning rate is 0.0100. Up to batch 0, the average loss is 5.33. Up to batch 1, the average loss is 4.84. Up to batch 2, the average loss is 4.02. Up to batch 3, the average loss is 3.87. Up to batch 4, the average loss is 3.85. The average loss for epoch 8 is 3.85 and mean absolute error is 1.53. Epoch 00009: Learning rate is 0.0050. Up to batch 0, the average loss is 1.84. Up to batch 1, the average loss is 2.75. Up to batch 2, the average loss is 3.16. Up to batch 3, the average loss is 3.52. Up to batch 4, the average loss is 3.34. The average loss for epoch 9 is 3.34 and mean absolute error is 1.43. Epoch 00010: Learning rate is 0.0050. Up to batch 0, the average loss is 2.36. Up to batch 1, the average loss is 2.91. Up to batch 2, the average loss is 2.63. Up to batch 3, the average loss is 2.93. Up to batch 4, the average loss is 3.17. The average loss for epoch 10 is 3.17 and mean absolute error is 1.36. Epoch 00011: Learning rate is 0.0050. Up to batch 0, the average loss is 3.32. Up to batch 1, the average loss is 3.02. Up to batch 2, the average loss is 2.96. Up to batch 3, the average loss is 2.80. Up to batch 4, the average loss is 2.92. The average loss for epoch 11 is 2.92 and mean absolute error is 1.32. Epoch 00012: Learning rate is 0.0010. Up to batch 0, the average loss is 4.11. Up to batch 1, the average loss is 3.70. Up to batch 2, the average loss is 3.89. Up to batch 3, the average loss is 3.76. Up to batch 4, the average loss is 3.45. The average loss for epoch 12 is 3.45 and mean absolute error is 1.44. Epoch 00013: Learning rate is 0.0010. Up to batch 0, the average loss is 3.38. Up to batch 1, the average loss is 3.34. Up to batch 2, the average loss is 3.26. Up to batch 3, the average loss is 3.56. Up to batch 4, the average loss is 3.62. The average loss for epoch 13 is 3.62 and mean absolute error is 1.44. Epoch 00014: Learning rate is 0.0010. Up to batch 0, the average loss is 2.48. Up to batch 1, the average loss is 2.38. Up to batch 2, the average loss is 2.76. Up to batch 3, the average loss is 2.63. Up to batch 4, the average loss is 2.66. The average loss for epoch 14 is 2.66 and mean absolute error is 1.29. <keras.callbacks.History at 0x7fd08446c290>
Yerleşik Keras geri aramaları
Okuyarak mevcut Keras geri aramalar kontrol etmeyi unutmayın API docs . Uygulamalar, CSV'ye giriş yapmayı, modeli kaydetmeyi, TensorBoard'da metrikleri görselleştirmeyi ve çok daha fazlasını içerir!