Iterative Deep Neural Network Quantization with Lipschitz Constraint

Network quantization offers an effective solution to deep neural network compression for practical usage. Existing network quantization methods cannot theoretically guarantee the convergence. This paper proposes a novel iterative framework for network quantization with arbitrary bit-widths. We present two Lipschitz constraint based quantization strategies, namely width-level network quantization (WLQ) and multi-level network quantization (MLQ), for high-bit and extremely low-bit (ternary) quantization, respectively. In WLQ, Lipschitz based partition is developed to divide parameters in each layer into two groups: one for quantization and the other for re-training to eliminate the quantization loss. WLQ is further extended to MLQ by introducing layer partition to suppress the quantization loss for extremely low bit-widths. The Lipschitz based partition is proven to guarantee the convergence of the quantized networks. Moreover, the proposed framework is complementary to network compression methods such as activation quantization, pruning and efficient network architectures. The proposed framework is evaluated over extensive state-of-the-art deep neural networks, i.e., AlexNet, VGG-16, GoogleNet and ResNet18. Experimental results show that the proposed framework improves the performance of tasks like classification, object detection and semantic segmentation.