Enabling NVM-based deep learning acceleration using nonuniform data quantization: work-in-progress

Apart from employing a co-processor (e.g., GPU) for neural network (NN) computation, utilizing the unique characteristics of nonvolatile memories (NVM), including RRAM, phase change memory (PCM), and STT-MRAM, to accelerate NN algorithms has been extensively studied. In such approaches, input data and synaptic weights are represented using word line voltages and cell resistance, with the resulting bit line current indicating the calculation result. However, the limited number of resistance levels in a NVM cell largely reduces the algorithm data precision, thus significantly lowering the model inference accuracy. Motivated by the observation that the conventional, uniformly generated data quantization points are not equally important to the model, we propose a nonuniform data quantization scheme to better represent the model in NVM cells and minimize the inference accuracy loss. Our experimental results show that the proposed scheme can achieve highly accurate deep learning model inference using as low as only 4 bits for synaptic weight representation. This effectively enables a NVM with few cell resistance levels (e.g., STT-MRAM) to perform NN calculation, and also results in additional benefits in performance, energy, and memory storage.