In the context of autoencoders the input and output of the model is the same. So, if the input values are in the range [0,1] then it is acceptable to use sigmoid as the activation function of last layer. Otherwise, you need to use an appropriate activation function for the last layer (e.g. linear which … Read more
Generally speaking, DBNs are generative neural networks that stack Restricted Boltzmann Machines (RBMs) . You can think of RBMs as being generative autoencoders; if you want a deep belief net you should be stacking RBMs and not plain autoencoders as Hinton and his student Yeh proved that stacking RBMs results in sigmoid belief nets. Convolutional … Read more
I’ll try to answer the original question of why model.add_loss() is being used instead of specifying a custom loss function to model.compile(loss=…). All loss functions in Keras always take two parameters y_true and y_pred. Have a look at the definition of the various standard loss functions available in Keras, they all have these two parameters. … Read more