RTF-Q: Unsupervised domain adaptation based retraining-free quantization network

Performing unsupervised domain adaptation on resource-constrained edge devices is a significant task. Although existing research allows edge devices to use subnets with different computational budgets for inference, they often require expensive pre-training and do not consider the issues of parameter precision redundancy in the model, which is not conducive to the deployment of the model on edge devices. In this paper, we introduce a ReTraining-Free Quantized (RTF-Q) network based on unsupervised domain adaptation, featuring quantized subnets of varying computational costs that can operate on devices with dynamically changing computation budgets. Our network has three switchable dimensions: width (number of channels), input resolution, and quantization bit-width. Specifically, we choose subnet dimensions that have minimal impact on network performance and then directly load the official weight files without requiring expensive and time-consuming pre-training on Imagenet-1K. To further reduce the network's computational load and memory usage, we use quantization-aware training, reducing the BitOPs of full-precision networks by at least 1/16. We propose a training method called SandwichQ for multiple quantization bit widths, which can efficiently train multiple quantization subnets. By training in multiple quantization bit-width spaces simultaneously and using the proposed SandwichQ rule, we achieve better network performance compared to using a single quantization bit-width alone. Experimental results show that our method achieves classification accuracy comparable to SOTA methods on various UDA tasks, significantly reducing network size and computational overhead. Code will be available at https://github.com/dunanyang/RTF-Q.