Resilience-Aware Frequency Tuning for Neural-Network-Based Approximate Computing Chips

Unlike conventional ICs, approximate computing chips are less sensitive to hardware errors. This fascinating feature can be utilized to improve the performance of chip design and even change the timing closure procedure of digital circuit design flow. In this paper, we study the potential of resilience-aware circuit clocking scheme, and demonstrate the methodology with advanced neural network (NN)-based accelerator. We propose a novel timing analysis and frequency setting method for NN-based approximate computing circuits based on in-field NN retraining. With the proposed iterative retiming-and-retraining framework, NN-based accelerator can be retrained to operate safely at aggressive operating frequencies compared with the frequency decided purely by statistical timing analysis or Monto Carlo analysis. For nanometer process technology with increasing threats of timing errors induced by process variation, noises, and so on, our retiming-and-retraining method enables higher circuit operating frequency and enables dynamic precision/frequency adjustment for approximate computing circuits. We evaluate the methodology with both the neural and deep learning accelerators in experiments. The experimental results show that timing errors in neural circuits can be effectively tamed for different applications, so that the circuits can operate at higher clocking rates under the specified quality constraint or be dynamically scaled to work at a wide range of frequency states with only minor accuracy losses.