LT-OAQ: Learnable Threshold Based Outlier-Aware Quantization and its Energy-Efficient Accelerator for Low-Precision On-Chip Training

Low-precision training has emerged as a powerful technique for reducing computational and storage costs in Deep Neural Network (DNN) model training, enabling on-chip training or fine-tuning on edge devices. However, existing low-precision training methods often require higher bit-widths to maintain accuracy as model sizes increase. In this paper, we introduce an outlier-aware quantization strategy for low-precision training. While traditional value-aware quantization methods require costly online distribution statistics operations on computational data, impeding the efficiency gains of low-precision training, our approach addresses this challenge through a novel Learnable Threshold based Outlier-Aware Quantization (LT-OAQ) training framework. This method concurrently updates outlier thresholds and model weights through gradient descent, eliminating the need for costly data-statistics operations. To efficiently support the LT-OAQ training framework, we designed a hardware accelerator based on the systolic array architecture. This accelerator introduces a processing element (PE) fusion mechanism that dynamically fuses adjacent PEs into clusters to support outlier computations, optimizing the mapping of outlier computation tasks, enabling mixed-precision training, and implementing online quantization. Our approach maintains model accuracy while significantly reducing computational complexity and storage resource requirements. Experimental results demonstrate that our design achieves a 2.9 ×speedup in performance and a 2.17 ×reduction in energy consumption compared to state-of-the-art low-precision accelerators.