  Unsupervised domain adaptation aims to transfer knowledge from a labeled
source domain to an unlabeled target domain. Previous methods focus on learning
domain-invariant features to decrease the discrepancy between the feature
distributions as well as minimizing the source error and have made remarkable
progress. However, a recently proposed theory reveals that such a strategy is
not sufficient for a successful domain adaptation. It shows that besides a
small source error, both the discrepancy between the feature distributions and
the discrepancy between the labeling functions should be small across domains.
The discrepancy between the labeling functions is essentially the cross-domain
errors which are ignored by existing methods. To overcome this issue, in this
paper, a novel method is proposed to integrate all the objectives into a
unified optimization framework. Moreover, the incorrect pseudo labels widely
used in previous methods can lead to error accumulation during learning. To
alleviate this problem, the pseudo labels are obtained by utilizing structural
information of the target domain besides source classifier and we propose a
curriculum learning based strategy to select the target samples with more
accurate pseudo-labels during training. Comprehensive experiments are
conducted, and the results validate that our approach outperforms
state-of-the-art methods.
