A Robust and Energy Efficient Hyperdimensional Computing System for Voltage-scaled Circuits

Voltage scaling is one of the most promising approaches for energy efficiency improvement but also brings challenges to fully guaranteeing stable operation in modern VLSI. To tackle such issues, we further extend the DependableHD to the second version DependableHDv2 , a HyperDimensional Computing (HDC) system that can tolerate bit-level memory failure in the low voltage region with high robustness. DependableHDv2 introduces the concept of margin enhancement for model retraining and utilizes noise injection to improve the robustness, which is capable of application in most state-of-the-art HDC algorithms. We additionally propose the dimension-swapping technique, which aims at handling the stuck-at errors induced by aggressive voltage scaling in the memory cells. Our experiment shows that under 8% memory stuck-at error, DependableHDv2 exhibits a 2.42% accuracy loss on average, which achieves a 14.1 × robustness improvement compared to the baseline HDC solution. The hardware evaluation shows that DependableHDv2 supports the systems to reduce the supply voltage from 430mV to 340mV for both item Memory and Associative Memory, which provides a 41.8% energy consumption reduction while maintaining competitive accuracy performance.