Meta-reweighted Regularization for Unsupervised Domain Adaptation
Shuang Li, Wenxuan Ma, Jinming Zhang, Chi Harold Liu, Jian Liang, Guoren Wang · IEEE Transactions on Knowledge and Data Engineering · 2021
Unsupervised domain adaptation enables knowledge transfer from a labeled source domain to an unlabeled target domain by reducing the cross-domain distribution discrepancy, and the adversarial learning based paradigm has achieved remarkable success. On top of this, recent works seeks to further regularize the classification decision boundary via self-training to learn target adaptive classifier with pseudo-labeled target samples. However, since pseudo labels are inevitably noisy, most of prior methods focus on manually designing elaborate target selection algorithms or optimization objectives. Different from them, we propose a meta-learning based target-reweighting regularization algorithm called MetaReg. Specifically, MetaReg is motivated by the intuition that an ideal target classifier trained on correct target pseudo labels should make small classification errors on target-like source samples. Therefore, we explicitly define a meta reweighting problem that aims to find optimal weights for different samples by minimizing the classification loss on a class-balanced set consisting of source samples that are most similar to target ones. The optimization problem is solved efficiently with a simplified approximation technique. As a result, the automatically learned optimal weights are utilized to reweight pseudo-labeled target samples and regularize the model learning. Comprehensive experiments verify that MetaReg outperforms the non-regularized UDA counterparts with state-of-the-art performance.