DC-AC: Deep Correlation-based Adaptive Compression of Feature Map Planes in Convolutional Neural Networks

Deep learning has been successfully deployed to a broad range of applications with its outstanding performance. Supporting an efficient hardware architecture is critical to making effective use of a deep learning approach with proven algorithm performance. One challenge in implementation of deep learning algorithm is to reduce memory bandwidth because a single memory access normally consumes 100* more energy than an arithmetic operation. To reduce the memory bandwidth, deep learning data could be compressed and decompressed before memory write/read operations. Especially, feature maps, which account for a significant portion of the convolutional neural network (CNN), could be compressed further by reducing the correlations between feature map planes. This paper proposes a compression method for feature maps in CNN that adaptively exploits the varying correlation between feature map planes. For every feature map plane, the proposed method searches the most similar plane among nearby planes in the same layer, and compresses the residual of the two planes instead of the plane itself. Experimental results show that the average bit length to store feature maps is reduced by 14.2% compared to the compression without correlation reduction, and the CNN accuracy does not change and additional training is also not required because the proposed method applies lossless compression.