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keras處理欠擬合和過擬合的實(shí)例講解

更新時間：2020年05月25日 08:46:01 作者：Lzj000lzj

這篇文章主要介紹了keras處理欠擬合和過擬合的實(shí)例講解，具有很好的參考價值，希望對大家有所幫助。一起跟隨小編過來看看吧

baseline

import tensorflow.keras.layers as layers
baseline_model = keras.Sequential(
[
 layers.Dense(16, activation='relu', input_shape=(NUM_WORDS,)),
 layers.Dense(16, activation='relu'),
 layers.Dense(1, activation='sigmoid')
]
)
baseline_model.compile(optimizer='adam',
      loss='binary_crossentropy',
      metrics=['accuracy', 'binary_crossentropy'])
baseline_model.summary()

baseline_history = baseline_model.fit(train_data, train_labels,
          epochs=20, batch_size=512,
          validation_data=(test_data, test_labels),
          verbose=2)

小模型

small_model = keras.Sequential(
[
 layers.Dense(4, activation='relu', input_shape=(NUM_WORDS,)),
 layers.Dense(4, activation='relu'),
 layers.Dense(1, activation='sigmoid')
]
)
small_model.compile(optimizer='adam',
      loss='binary_crossentropy',
      metrics=['accuracy', 'binary_crossentropy'])
small_model.summary()
small_history = small_model.fit(train_data, train_labels,
          epochs=20, batch_size=512,
          validation_data=(test_data, test_labels),
          verbose=2)

大模型

big_model = keras.Sequential(
[
 layers.Dense(512, activation='relu', input_shape=(NUM_WORDS,)),
 layers.Dense(512, activation='relu'),
 layers.Dense(1, activation='sigmoid')
]
)
big_model.compile(optimizer='adam',
      loss='binary_crossentropy',
      metrics=['accuracy', 'binary_crossentropy'])
big_model.summary()
big_history = big_model.fit(train_data, train_labels,
          epochs=20, batch_size=512,
          validation_data=(test_data, test_labels),
          verbose=2)

繪圖比較上述三個模型

def plot_history(histories, key='binary_crossentropy'):
 plt.figure(figsize=(16,10))
 
 for name, history in histories:
 val = plt.plot(history.epoch, history.history['val_'+key],
     '--', label=name.title()+' Val')
 plt.plot(history.epoch, history.history[key], color=val[0].get_color(),
    label=name.title()+' Train')

 plt.xlabel('Epochs')
 plt.ylabel(key.replace('_',' ').title())
 plt.legend()

 plt.xlim([0,max(history.epoch)])


plot_history([('baseline', baseline_history),
    ('small', small_history),
    ('big', big_history)])

三個模型在迭代過程中在訓(xùn)練集的表現(xiàn)都會越來越好，并且都會出現(xiàn)過擬合的現(xiàn)象

大模型在訓(xùn)練集上表現(xiàn)更好，過擬合的速度更快

l2正則減少過擬合

l2_model = keras.Sequential(
[
 layers.Dense(16, kernel_regularizer=keras.regularizers.l2(0.001), 
     activation='relu', input_shape=(NUM_WORDS,)),
 layers.Dense(16, kernel_regularizer=keras.regularizers.l2(0.001), 
     activation='relu'),
 layers.Dense(1, activation='sigmoid')
]
)
l2_model.compile(optimizer='adam',
      loss='binary_crossentropy',
      metrics=['accuracy', 'binary_crossentropy'])
l2_model.summary()
l2_history = l2_model.fit(train_data, train_labels,
          epochs=20, batch_size=512,
          validation_data=(test_data, test_labels),
          verbose=2)
plot_history([('baseline', baseline_history),
    ('l2', l2_history)])

可以發(fā)現(xiàn)正則化之后的模型在驗證集上的過擬合程度減少

添加dropout減少過擬合

dpt_model = keras.Sequential(
[
 layers.Dense(16, activation='relu', input_shape=(NUM_WORDS,)),
 layers.Dropout(0.5),
 layers.Dense(16, activation='relu'),
 layers.Dropout(0.5),
 layers.Dense(1, activation='sigmoid')
]
)
dpt_model.compile(optimizer='adam',
      loss='binary_crossentropy',
      metrics=['accuracy', 'binary_crossentropy'])
dpt_model.summary()
dpt_history = dpt_model.fit(train_data, train_labels,
          epochs=20, batch_size=512,
          validation_data=(test_data, test_labels),
          verbose=2)
plot_history([('baseline', baseline_history),
    ('dropout', dpt_history)])

批正則化

model = keras.Sequential([
 layers.Dense(64, activation='relu', input_shape=(784,)),
 layers.BatchNormalization(),
 layers.Dense(64, activation='relu'),
 layers.BatchNormalization(),
 layers.Dense(64, activation='relu'),
 layers.BatchNormalization(),
 layers.Dense(10, activation='softmax')
])
model.compile(optimizer=keras.optimizers.SGD(),
    loss=keras.losses.SparseCategoricalCrossentropy(),
    metrics=['accuracy'])
model.summary()
history = model.fit(x_train, y_train, batch_size=256, epochs=100, validation_split=0.3, verbose=0)
plt.plot(history.history['accuracy'])
plt.plot(history.history['val_accuracy'])
plt.legend(['training', 'validation'], loc='upper left')
plt.show()

總結(jié)

防止神經(jīng)網(wǎng)絡(luò)中過度擬合的最常用方法：

獲取更多訓(xùn)練數(shù)據(jù)。

減少網(wǎng)絡(luò)容量。

添加權(quán)重正規(guī)化。

添加dropout。

以上這篇keras處理欠擬合和過擬合的實(shí)例講解就是小編分享給大家的全部內(nèi)容了，希望能給大家一個參考，也希望大家多多支持腳本之家。

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