Abstract
There is growing interest in improving the design of deep
network architectures to be both accurate and low cost.
This paper explores semantic specialization as a mechanism for improving the computational efficiency (accuracyper-unit-cost) of inference in the context of image classifi-
cation. Specifically, we propose a network architecture template called HydraNet, which enables state-of-the-art architectures for image classification to be transformed into dynamic architectures which exploit conditional execution for
efficient inference. HydraNets are wide networks containing distinct components specialized to compute features for
visually similar classes, but they retain efficiency by dynamically selecting only a small number of components to evaluate for any one input image. This design is made possible
by a soft gating mechanism that encourages component specialization during training and accurately performs component selection during inference. We evaluate the HydraNet
approach on both the CIFAR-100 and ImageNet classification tasks. On CIFAR, applying the HydraNet template to
the ResNet and DenseNet family of models reduces inference cost by 2-4× while retaining the accuracy of the baseline architectures. On ImageNet, applying the HydraNet
template improves accuracy up to 2.5% when compared to
an efficient baseline architecture with similar inference cost