Residue-Net: Multiplication-free Neural Network by In-situ No-loss Migration to Residue Number Systems

Abstract

Deep eural networks are widely deployed on embedded devices to solve a wide range of problems from edge-sensing to autonomous driving. The accuracy of these networks is usually proportional to their complexity. Quantization of model parameters (i.e., weights) and/or activations to alleviate the complexity of these networks while preserving accuracy is a popular powerful technique. Nonetheless, previous studies have shown that quantization level is limited as the accuracy of the network decreases afterward. We propose Residue-Net, a multiplication-free accelerator for neural networks that uses Residue Number System (RNS) to achieve substantial energy reduction. RNS breaks down the operations to several smaller operations that are simpler to implement. Moreover, Residue-Net replaces the copious of costly multiplications with non-complex, energy-efficient shift and add operations to further simplify the computational complexity of neural networks. To evaluate the efficiency of our proposed accelerator, we compared the performance of Residue-Net with a baseline FPGA implementation of four widely-used networks, viz., LeNet, AlexNet, VGG16, and ResNet-50. When delivering the same performance as the baseline, Residue-Net reduces the area and power (hence energy) respectively by 36% and 23%, on average with no accuracy loss. Leveraging the saved area to accelerate the quantized RNS network through parallelism, Residue-Net improves its throughput by 2.8× and energy by 2.7×.