Conditional Support Alignment for Domain Adaptation with Label Shift
Anh T Nguyen Lam Tran Anh Tong Tuan-Duy H. Nguyen Toan Tran
Unsupervised domain adaptation (UDA) refers to a domain adaptation framework
in which a learning model is trained based on the labeled samples on the source
domain and unlabelled ones in the target domain. The dominant existing methods
in the field that rely on the classical covariate shift assumption to learn
domain-invariant feature representation have yielded suboptimal performance
under the label distribution shift between source and target domains. In this
paper, we propose a novel conditional adversarial support alignment (CASA)
whose aim is to minimize the conditional symmetric support divergence between
the source's and target domain's feature representation distributions, aiming
at a more helpful representation for the classification task. We also introduce
a novel theoretical target risk bound, which justifies the merits of aligning
the supports of conditional feature distributions compared to the existing
marginal support alignment approach in the UDA settings. We then provide a
complete training process for learning in which the objective optimization
functions are precisely based on the proposed target risk bound. Our empirical
results demonstrate that CASA outperforms other state-of-the-art methods on
different UDA benchmark tasks under label shift conditions.