SkipNet: Learning Dynamic Routing in Convolutional Networks

Increasing depth and complexity in convolutional neural networks has enabled significant progress in visual perception tasks. However, incremental improvements in accuracy are often accompanied by exponentially deeper models that push the computational limits of modern hardware. These incremental improvements in accuracy imply that only a small fraction of the inputs require the additional model complexity. As a consequence, for any given image it is possible to bypass multiple stages of computation to reduce the cost of forward inference without affecting accuracy. We exploit this simple observation by learning to dynamically route computation through a convolutional network. We introduce dynamically routed networks (SkipNets) by adding gating layers that route images through existing convolutional networks and formulate the routing problem in the context of sequential decision making. We propose a hybrid learning algorithm which combines supervised learning and reinforcement learning to address the challenges of inherently non-differentiable routing decisions. We show SkipNet reduces computation by 30 90% while preserving the accuracy of the original model on four benchmark datasets. We compare SkipNet with SACT and ACT to show SkipNet achieves better accuracy with lower computation.