Hybrid Post-Training Quantization for Super-Resolution Neural Network Compression

Quantization is a widely adopted technique to reduce the storage cost of neural networks. However, existing methods primarily focus on minimizing the quantization error of neural network parameters without considering the correlation between the quantization error and performance of quantized neural networks. Motivated by this consideration, we propose a hybrid post-training quantization (HPTQ) method for super-resolution neural networks. Layer-wise quantization and piecewise quantization are integrated based on error sensitivity and the quantization error of parameters. In HPTQ, we utilize Taylor expansion to demonstrate that the performance distortion of quantized neural networks is a weighted average of parameter quantization errors with respect to gradients. To reduce the quantization error, we apply uniform and clustered quantization to parameters in dense and sparse regions, respectively. Furthermore, we allocate larger bit-widths to layers with higher error sensitivity indicated by gradients. Numerical experiments show that the super-resolution neural networks perform better under the proposed quantization approach compared to existing quantization methods.