QDrop: Randomly Dropping Quantization for Extremely Low-bit Post-Training Quantization
This work addresses the challenge of efficient neural network deployment for practitioners by enabling low-bit quantization without retraining, representing a significant advance rather than an incremental improvement.
The paper tackles the problem of post-training quantization (PTQ) failing at extremely low-bit settings by proposing QDrop, a method that randomly drops activation quantization during PTQ, which pushes PTQ to 2-bit activations for the first time and achieves accuracy boosts of up to 51.49%.
Recently, post-training quantization (PTQ) has driven much attention to produce efficient neural networks without long-time retraining. Despite its low cost, current PTQ works tend to fail under the extremely low-bit setting. In this study, we pioneeringly confirm that properly incorporating activation quantization into the PTQ reconstruction benefits the final accuracy. To deeply understand the inherent reason, a theoretical framework is established, indicating that the flatness of the optimized low-bit model on calibration and test data is crucial. Based on the conclusion, a simple yet effective approach dubbed as QDROP is proposed, which randomly drops the quantization of activations during PTQ. Extensive experiments on various tasks including computer vision (image classification, object detection) and natural language processing (text classification and question answering) prove its superiority. With QDROP, the limit of PTQ is pushed to the 2-bit activation for the first time and the accuracy boost can be up to 51.49%. Without bells and whistles, QDROP establishes a new state of the art for PTQ. Our code is available at https://github.com/wimh966/QDrop and has been integrated into MQBench (https://github.com/ModelTC/MQBench)