How to use advanced activation layers in Keras?

Question

This is my code that works if I use other activation layers like tanh:

model = Sequential()
act = keras.layers.advanced_activations.PReLU(init='zero', weights=None)
model.add(Dense(64, input_dim=14, init='uniform'))
model.add(Activation(act))
model.add(Dropout(0.15))
model.add(Dense(64, init='uniform'))
model.add(Activation('softplus'))
model.add(Dropout(0.15))
model.add(Dense(2, init='uniform'))
model.add(Activation('softmax'))

sgd = SGD(lr=0.1, decay=1e-6, momentum=0.9, nesterov=True)
model.compile(loss='binary_crossentropy', optimizer=sgd)
model.fit(X_train, y_train, nb_epoch=20, batch_size=16, show_accuracy=True, validation_split=0.2, verbose = 2)

In this case, it doesn't work and says "TypeError: 'PReLU' object is not callable" and the error is called at the model.compile line. Why is this the case? All the non-advanced activation functions works. However, neither of the advanced activation functions, including this one, works.

Answer 1

The correct way to use the advanced activations like PReLU is to use it with add() method and not wrapping it using Activation class. Example:

model = Sequential()
act = keras.layers.advanced_activations.PReLU(init='zero', weights=None)
model.add(Dense(64, input_dim=14, init='uniform'))
model.add(act)