Reviewed Version (pdf): https://openreview.net/references/pdf?id=qEtMlX0z6s
Keywords: attention, hard attention, variational inference, bayesian optimal experimental design
Abstract: Hard visual attention is a promising approach to reduce the computational burden of modern computer vision methodologies. Hard attention mechanisms are typically non-differentiable. They can be trained with reinforcement learning but the high-variance training this entails hinders more widespread application. We show how hard attention for image classification can be framed as a Bayesian optimal experimental design (BOED) problem. From this perspective, the optimal locations to attend to are those which provide the greatest expected reduction in the entropy of the classification distribution. We introduce methodology from the BOED literature to approximate this optimal behaviour, and use it to generate `near-optimal' sequences of attention locations. We then show how to use such sequences to partially supervise, and therefore speed up, the training of a hard attention mechanism. Although generating these sequences is computationally expensive, they can be reused by any other networks later trained on the same task.
One-sentence Summary: We use Bayesian experimental design to produce sequences which are later used to provide a supervision signal for a hard attention network and greatly speed up its training.
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