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 import Activation, Dense

model.add(Dense(64))
model.add(Activation('tanh'))

This is equivalent to:

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

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

from keras import backend as K

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

Available activations

elu

elu(x, alpha=1.0)

---

selu

selu(x)

Scaled Exponential Linear Unit. (Klambauer et al., 2017)

Arguments

• x: A tensor or variable to compute the activation function for.

References

• Self-Normalizing Neural Networks

---

softplus

softplus(x)

---

softsign

softsign(x)

---

relu

relu(x, alpha=0.0, max_value=None)

---

tanh

tanh(x)

---

sigmoid

sigmoid(x)

---

hard_sigmoid

hard_sigmoid(x)

---

linear

linear(x)

---

softmax

softmax(x, axis=-1)

Softmax activation function.

Arguments

x : Tensor. - axis: Integer, axis along which the softmax normalization is applied.

Returns

Tensor, output of softmax transformation.

Raises

• ValueError: In case dim(x) == 1.

On "Advanced Activations"

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