  Whereas deep neural networks were first mostly used for classification tasks,
they are rapidly expanding in the realm of structured output problems, where
the observed target is composed of multiple random variables that have a rich
joint distribution, given the input. We focus in this paper on the case where
the input also has a rich structure and the input and output structures are
somehow related. We describe systems that learn to attend to different places
in the input, for each element of the output, for a variety of tasks: machine
translation, image caption generation, video clip description and speech
recognition. All these systems are based on a shared set of building blocks:
gated recurrent neural networks and convolutional neural networks, along with
trained attention mechanisms. We report on experimental results with these
systems, showing impressively good performance and the advantage of the
attention mechanism.
