CDTrans: Cross-domain Transformer for Unsupervised Domain Adaptation

TL;DR

CDTrans introduces a pure transformer-based approach for unsupervised domain adaptation, utilizing a novel labeling algorithm and a triple-branch framework to improve domain alignment and feature learning.

Contribution

This work is the first to apply a pure transformer architecture to UDA, combining self-attention and cross-attention with a center-aware pseudo labeling method.

Findings

Achieves state-of-the-art results on VisDA-2017 and DomainNet datasets.

Outperforms CNN-based UDA methods in domain alignment accuracy.

Demonstrates robustness of transformer-based models in noisy pseudo label scenarios.

Abstract

Unsupervised domain adaptation (UDA) aims to transfer knowledge learned from a labeled source domain to a different unlabeled target domain. Most existing UDA methods focus on learning domain-invariant feature representation, either from the domain level or category level, using convolution neural networks (CNNs)-based frameworks. One fundamental problem for the category level based UDA is the production of pseudo labels for samples in target domain, which are usually too noisy for accurate domain alignment, inevitably compromising the UDA performance. With the success of Transformer in various tasks, we find that the cross-attention in Transformer is robust to the noisy input pairs for better feature alignment, thus in this paper Transformer is adopted for the challenging UDA task. Specifically, to generate accurate input pairs, we design a two-way center-aware labeling algorithm to produce pseudo labels for target samples. Along with the pseudo labels, a weight-sharing triple-branch transformer framework is proposed to apply self-attention and cross-attention for source/target feature learning and source-target domain alignment, respectively. Such design explicitly enforces the framework to learn discriminative domain-specific and domain-invariant representations simultaneously. The proposed method is dubbed CDTrans (cross-domain transformer), and it provides one of the first attempts to solve UDA tasks with a pure transformer solution. Experiments show that our proposed method achieves the best performance on public UDA datasets, e.g. VisDA-2017 and DomainNet. Code and models are available at https://github.com/CDTrans/CDTrans.