Introduction
Addressing the challenge of domain adaptation in LLMs (LMs), a new paradigm within unsupervised domain adaptation (UDA) has emerged, called prompt-based UDA. This approach utilizes prompt templates to convert discriminative predictions into generative tasks, allowing for the adaptation to the target domain without relying on domain-invariant representations or extended pre-training.
Methodology
The paper introduces the FEUDA (Frustratingly Easy UDA) method, which comprises two instruction-tuning tasks. The initial task involves masked LLMing (MLM) using unlabeled data from both the source and target domains. The subsequent task leverages supervised instruction-tuning with labeled source data for classification. The integration of these tasks effectively bridges the gap between pre-training and adaptation, enhancing the LM's performance on the target domain.
Results
Extensive experiments on 24 real-world domain pairs demonstrate FEUDA's superiority over traditional domain-invariant methods. A noteworthy finding is that MLM within FEUDA augments the model's semantic and background knowledge of a domain, contributing positively to downstream classification tasks. The research reveals significant improvements in target-domain classification performance, even in few-shot learning scenarios and across various models and adaptation techniques.
Analysis and Extensions
The authors delve into the effects of MLM on UDA by analyzing the importance of masked words selection and varying masking rates. They find that the presence of both informative and uninformative words, identified through PMI, is crucial for achieving high classification accuracy. Additionally, the paper explores the impact of different masking rates, highlighting that optimal performance is attained at a 15% masking rate, while higher rates negatively affect the target domain's classification.
Conclusion
The paper concludes that domain invariance is not a necessity in prompt-based UDA—an insight that sets the stage for future explorations. FEUDA stands as a robust and competitive method, providing a simple yet effective solution for UDA challenges in LMs. As researchers and practitioners aim for better adaptability in real-world applications, FEUDA offers a promising direction.