Toward Low-Bit Neural Network Training Accelerator by Dynamic Group Accumulation

Low-bit quantization is a big challenge for neural network training. Conventional training hardware adopts FP32 to accumulate the partial-sum result, which seriously degrades energy efficiency. In this paper, a technology called dynamic group accumulation (DGA) is proposed to reduce the accumulation error. First, we model the proposed group accumulation method and give the optimal DGA algorithm. Second, we design a training architecture and implement a hardware-efficient DGA unit. Third, we make a comprehensive analysis of the DGA algorithm and training architecture. The proposed method is evaluated on CIFAR and ImageNet datasets, and results show that DGA can reduce accumulation bit-width by 6 bits while achieving the same precision as the static group method. With the FP12 DGA, the CNN algorithm only loses 0.11% accuracy in ImageNet training, and our architecture saves 32% of power consumption compared to the FP32 baseline.