Usage of activations

Activations can either be used through an Activation layer, or through the activation argument supported by all forward layers:

from keras.layers.core import Activation, Dense


is equivalent to:

model.add(Dense(64, activation='tanh'))

You can also pass an element-wise Theano/TensorFlow function as an activation:

from keras import backend as K

def tanh(x):
    return K.tanh(x)

model.add(Dense(64, activation=tanh))

Available activations

  • softmax: Softmax applied across inputs last dimension. Expects shape either (nb_samples, nb_timesteps, nb_dims) or (nb_samples, nb_dims).
  • softplus
  • softsign
  • relu
  • tanh
  • sigmoid
  • hard_sigmoid
  • linear

On Advanced Activations

Activations that are more complex than a simple Theano/TensorFlow function (eg. learnable activations, configurable activations, etc.) are available as Advanced Activation layers, and can be found in the module keras.layers.advanced_activations. These include PReLU and LeakyReLU.