Certifying Better Robust Generalization for Unsupervised Domain Adaptation

Recent studies explore how to obtain adversarial robustness for unsupervised domain adaptation (UDA). These efforts are however dedicated to achieving an optimal trade-off between accuracy and robustness on a given or seen target domain but ignore the robust generalization issue over unseen adversarial data. Consequently, degraded performance will be often observed when existing robust UDAs are applied to future adversarial data. In this work, we make a first attempt to address the robust generalization issue of UDA. We conjecture that the poor robust generalization of present robust UDAs may be caused by the large distribution gap among adversarial examples. We then provide an empirical and theoretical analysis showing that this large distribution gap is mainly owing to the discrepancy between feature-shift distributions. To reduce such discrepancy, a novel Anchored Feature-Shift Regularization (AFSR) method is designed with a certificated robust generalization bound. We conduct a series of experiments on benchmark UDA datasets. Experimental results validate the effectiveness of our proposed AFSR over many existing robust UDA methods.