index.md

Optimizers

Available optimizers

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Usage with compile() & fit()

An optimizer is one of the two arguments required for compiling a Keras model:

import keras
from keras import layers

model = keras.Sequential()
model.add(layers.Dense(64, kernel_initializer='uniform', input_shape=(10,)))
model.add(layers.Activation('softmax'))

opt = keras.optimizers.Adam(learning_rate=0.01)
model.compile(loss='categorical_crossentropy', optimizer=opt)

You can either instantiate an optimizer before passing it to model.compile() , as in the above example, or you can pass it by its string identifier. In the latter case, the default parameters for the optimizer will be used.

# pass optimizer by name: default parameters will be used
model.compile(loss='categorical_crossentropy', optimizer='adam')

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Learning rate decay / scheduling

You can use a learning rate schedule to modulate how the learning rate of your optimizer changes over time:

lr_schedule = keras.optimizers.schedules.ExponentialDecay(
    initial_learning_rate=1e-2,
    decay_steps=10000,
    decay_rate=0.9)
optimizer = keras.optimizers.SGD(learning_rate=lr_schedule)

Check out the learning rate schedule API documentation for a list of available schedules.

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Base Optimizer API

These methods and attributes are common to all Keras optimizers.

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