CAKES: Channel-wise Automatic KErnel Shrinking for Efficient 3D Network

3D Convolution Neural Networks (CNNs) have been widely applied to 3D scene understanding, such as video analysis and volumetric image recognition. However, 3D networks can easily lead to over-parameterization which incurs expensive computation cost. In this paper, we propose Channel-wise Automatic KErnel Shrinking (CAKES), to enable efficient 3D learning by shrinking standard 3D convolutions into a set of economic operations (e.g., 1D, 2D convolutions). Unlike previous methods, our proposed CAKES performs channel-wise kernel shrinkage, which enjoys the following benefits: 1) encouraging operations deployed in every layer to be heterogeneous, so that they can extract diverse and complementary information to benefit the learning process; and 2) allowing for an efficient and flexible replacement design, which can be generalized to both spatial-temporal and volumetric data. Together with a neural architecture search framework, by applying CAKES to 3D C2FNAS and ResNet50, we achieve the state-of-the-art performance with much fewer parameters and computational costs on both 3D medical imaging segmentation and video action recognition.