Agile Multi-Source-Free Domain Adaptation
Xinyao Li, Jingjing Li, Fengling Li, Lei Zhu, Ke Lu
TL;DR
This work tackles Multi-Source-Free Domain Adaptation (MSFDA) by enabling adaptation from multiple source models to an unlabeled target without accessing source data. It introduces Bi-ATEN, a bi-level attention module that learns instance-specific intra-domain weights $alpha^i$ and domain-consistent inter-domain weights $beta$ to assemble cross-domain outputs while keeping source backbones fixed. Bi-ATEN achieves state-of-the-art results on DomainNet with less than $3\%$ of trainable parameters and up to $8\times$ throughput, and can be plugged into existing MSFDA methods to gain additional improvements. Extensive ablations and analyses demonstrate the importance of instance-specific and domain-consistent weighting and show that the approach scales to large backbones, offering a practical pathway for agile MSFDA in real-world deployments.
Abstract
Efficiently utilizing rich knowledge in pretrained models has become a critical topic in the era of large models. This work focuses on adaptively utilizing knowledge from multiple source-pretrained models to an unlabeled target domain without accessing the source data. Despite being a practically useful setting, existing methods require extensive parameter tuning over each source model, which is computationally expensive when facing abundant source domains or larger source models. To address this challenge, we propose a novel approach which is free of the parameter tuning over source backbones. Our technical contribution lies in the Bi-level ATtention ENsemble (Bi-ATEN) module, which learns both intra-domain weights and inter-domain ensemble weights to achieve a fine balance between instance specificity and domain consistency. By slightly tuning source bottlenecks, we achieve comparable or even superior performance on a challenging benchmark DomainNet with less than 3% trained parameters and 8 times of throughput compared with SOTA method. Furthermore, with minor modifications, the proposed module can be easily equipped to existing methods and gain more than 4% performance boost. Code is available at https://github.com/TL-UESTC/Bi-ATEN.
