Discriminative feature alignment: Improving transferability of unsupervised domain adaptation by Gaussian-guided latent alignment

In this paper, we focus on the unsupervised domain adaptation problem where an approximate inference model is to be learned from a labeled data domain and expected to generalize well to an unlabeled domain. The success of unsupervised domain adaptation largely relies on the cross-domain feature alignment. Previous work has attempted to directly align features by classifier-induced discrepancies. Nevertheless, a common feature space cannot always be learned via this direct feature alignment especially when large domain gaps exist. To solve this problem, we introduce a Gaussian-guided latent alignment approach to align the latent feature distributions of the two domains under the guidance of a prior. In such an indirect way, the distributions over the samples from the two domains will be constructed on a common feature space, i.e., the space of the prior, which promotes better feature alignment. To effectively align the target latent distribution with this prior distribution, we also propose a novel unpaired L1-distance by taking advantage of the formulation of the encoder-decoder. The extensive evaluations on nine benchmark datasets validate the superior knowledge transferability through outperforming state-ofthe-art methods and the versatility of the proposed method by improving the existing work significantly. (c) 2021 Elsevier Ltd. All rights reserved.