Semi-supervised domain adaptation (SSDA) aims to apply knowledge learned from a fully labeled source domain to a scarcely labeled target domain. In this paper, we propose a Multi-level Consistency Learning (MCL) framework for SSDA. Specifically, our MCL regularizes the consistency of different views of target domain samples at three levels: (i) at inter-domain level, we robustly and accurately align the source and target domains using a prototype-based optimal transport method that utilizes the pros and cons of different views of target samples; (ii) at intra-domain level, we facilitate the learning of both discriminative and compact target feature representations by proposing a novel class-wise contrastive clustering loss; (iii) at sample level, we follow standard practice and improve the prediction accuracy by conducting a consistency-based self-training. Empirically, we verified the effectiveness of our MCL framework on three popular SSDA benchmarks, i.e., VisDA2017, DomainNet, and Office-Home datasets, and the experimental results demonstrate that our MCL framework achieves the state-of-the-art performance.

本文提出了一种基于多级一致性学习的半监督域自适应框架，其中包括使用基于原型的最优传输方法稳健准确地对齐源域和目标域，使用新颖的类内对比聚类损失促进目标特征表示的学习，遵循标准实践并通过自我训练改进预测准确性等多种优化机制。实验证明，该框架在三个受欢迎的半监督域自适应基准测试中均取得了最新的性能表现。

半监督域自适应的多层一致性学习