Learning Receptive Field Size by Learning Filter Size

Abstract

Covering various receptive fields within a layer is essential to effectively recognize the objects of various sizes and types at a specific layer for a convolutional neural network (CNN). In this work, we propose a novel adaptive learning method which learns the filter size (i.e. the kernel size of a convolutional filter) and distribution to learn the receptive field size. Directly optimizing with respect to the filter size is challenging because the filter size is discrete. To overcome this, we propose a masking technique, which enables the automatic allocation of resources over filters of different sizes and leads to efficient optimization. Through our proposed trainable formulation of the mask, the network self-organizes its structure through the standard backpropagation. The proposed adaptive CNN can be generalized to any single-path structures and multi-path structures as well. The effectiveness of our proposed approach is validated by several benchmark datasets compared with various previous structures on the image classification task for diverse network depths and widths. Furthermore, we demonstrate our adaptive CNN trained on a large-scale dataset can yield improved performance when applying to a transfer learning.