Domain-Adaptive Few-Shot Learning (2003.08626v1)

Abstract: Existing few-shot learning (FSL) methods make the implicit assumption that the few target class samples are from the same domain as the source class samples. However, in practice this assumption is often invalid -- the target classes could come from a different domain. This poses an additional challenge of domain adaptation (DA) with few training samples. In this paper, the problem of domain-adaptive few-shot learning (DA-FSL) is tackled, which requires solving FSL and DA in a unified framework. To this end, we propose a novel domain-adversarial prototypical network (DAPN) model. It is designed to address a specific challenge in DA-FSL: the DA objective means that the source and target data distributions need to be aligned, typically through a shared domain-adaptive feature embedding space; but the FSL objective dictates that the target domain per class distribution must be different from that of any source domain class, meaning aligning the distributions across domains may harm the FSL performance. How to achieve global domain distribution alignment whilst maintaining source/target per-class discriminativeness thus becomes the key. Our solution is to explicitly enhance the source/target per-class separation before domain-adaptive feature embedding learning in the DAPN, in order to alleviate the negative effect of domain alignment on FSL. Extensive experiments show that our DAPN outperforms the state-of-the-art FSL and DA models, as well as their na\"ive combinations. The code is available at https://github.com/dingmyu/DAPN.

• The paper introduces a novel task and method that combines few-shot learning with domain adaptation using a prototypical network framework.
• The approach incorporates adversarial training and adaptive re-weighting to balance global domain alignment with precise class discrimination.
• Experiments on miniImageNet, tieredImageNet, and DomainNet demonstrate superior performance over traditional FSL and unsupervised domain adaptation methods.

Analyzing Domain-Adaptive Few-Shot Learning

The paper "Domain-Adaptive Few-Shot Learning" explores the intersection of two challenging tasks in machine learning: few-shot learning (FSL) and domain adaptation (DA). Few-shot learning is aimed at training models to recognize new classes with a limited number of annotated samples. However, traditional FSL methods presume that the few-shot samples originate from the same domain as the training data, an assumption that often fails in practical scenarios where domain discrepancies exist. Consequently, the authors introduce a novel task, domain-adaptive few-shot learning (DA-FSL), which demands both few-shot learning and domain adaptation capabilities.

Key Contributions

The authors propose a method called Domain-Adaptive Prototypical Network (DAPN) to tackle the DA-FSL problem. Central to this approach is the integration of a domain-adversarial component designed to align global data distributions from different domains, while ensuring discrimination among class distributions. This addresses the conflict where domain alignment objectives might undermine the class discrimination essential for FSL. DAPN achieves this by enhancing class separation before embedding and learning a domain-adaptive feature space.

The model incorporates multiple modules, including:

• Few-Shot Learning Module: Utilizes the episodic training method and prototypical network to learn class prototypes and classify based on distance metrics in the embedding space.
• Domain Adversarial Adaptation (DAA) Module: Combines autoencoding and attention mechanisms to project data into a feature space suitable for both domains. It also incorporates adversarial training to achieve domain confusion.
• Adaptive Re-weighting Module: Dynamically determines the balance between DA and FSL losses to maximize learning efficiency.

Experimental Results and Implications

Through extensive experimentation on both synthesized and real-world datasets—miniImageNet, tieredImageNet, and DomainNet—the proposed DAPN model demonstrates superior performance over existing FSL and UDA strategies, as well as naïve combinations of such methods. This underscores the importance of addressing domain discrepancies in few-shot scenarios and establishes DAPN's efficacy in doing so.

The results reveal that domain adaptation is crucial within the DA-FSL setting, suggesting that tackling domain gaps even with basic strategies like nearest neighbor classifiers can significantly enhance recognition tasks. The construct of DA-FSL as introduced invites more comprehensive explorations in adaptation strategies, especially given varying levels of domain shifts and class diversities.

Theoretical and Practical Implications

Theoretically, this research embodies an effective solution framework to the intrinsic tension between domain adaptation and per-class discriminativeness within few-shot learning. It widens the applicability scope of few-shot learning, which aligns well with realistic conditions of domain variability. Practically, the proposed method could be adapted for tasks where domain shifts are prevalent, such as cross-device and cross-environment image recognition.

Speculation on Future Developments

Future works might explore exploring deeper relationships between domain gaps and class property distribution, potentially integrating unsupervised learning to further reduce labeled resource dependence. Additionally, implementing such frameworks beyond visual data could broaden DA-FSL applicability to text, audio, and multi-modal datasets. Moreover, investigating more sophisticated embedding techniques or integrating neural architecture search could drive further improvements in efficiency and adaptability.

In conclusion, this paper provides a comprehensive investigation into DA-FSL and introduces a robust DAPN model, setting a new benchmark for research in bridging domain adaptation and few-shot learning.