Source-free Domain Adaptation via Avatar Prototype Generation and Adaptation
This addresses a practical problem in machine learning for scenarios with data privacy constraints, offering a novel approach to domain adaptation without access to source data.
The paper tackles source-free unsupervised domain adaptation, where only a pre-trained source model and unlabeled target data are available, by proposing a method to generate source avatar prototypes and align them with target data using contrastive learning, achieving state-of-the-art results on three benchmark datasets.
We study a practical domain adaptation task, called source-free unsupervised domain adaptation (UDA) problem, in which we cannot access source domain data due to data privacy issues but only a pre-trained source model and unlabeled target data are available. This task, however, is very difficult due to one key challenge: the lack of source data and target domain labels makes model adaptation very challenging. To address this, we propose to mine the hidden knowledge in the source model and exploit it to generate source avatar prototypes (i.e., representative features for each source class) as well as target pseudo labels for domain alignment. To this end, we propose a Contrastive Prototype Generation and Adaptation (CPGA) method. Specifically, CPGA consists of two stages: (1) prototype generation: by exploring the classification boundary information of the source model, we train a prototype generator to generate avatar prototypes via contrastive learning. (2) prototype adaptation: based on the generated source prototypes and target pseudo labels, we develop a new robust contrastive prototype adaptation strategy to align each pseudo-labeled target data to the corresponding source prototypes. Extensive experiments on three UDA benchmark datasets demonstrate the effectiveness and superiority of the proposed method.