Few-shot Fine-tuning vs. In-context Learning: A Fair Comparison and Evaluation

Original Paper: https://arxiv.org/abs/2305.16938

By: Marius Mosbach, Tiago Pimentel, Shauli Ravfogel, Dietrich Klakow, Yanai Elazar

Abstract:

Few-shot fine-tuning and in-context learning are two alternative strategies for task adaptation of pre-trained language models. Recently, in-context learning has gained popularity over fine-tuning due to its simplicity and improved out-of-domain generalization, and because extensive evidence shows that fine-tuned models pick up on spurious correlations. Unfortunately, previous comparisons of the two approaches were done using models of different sizes. This raises the question of whether the observed weaker out-of-domain generalization of fine-tuned models is an inherent property of fine-tuning or a limitation of the experimental setup. In this paper, we compare the generalization of few-shot fine-tuning and in-context learning to challenge datasets, while controlling for the models used, the number of examples, and the number of parameters, ranging from 125M to 30B. Our results show that fine-tuned language models can in fact generalize well out-of-domain. We find that both approaches generalize similarly; they exhibit large variation and depend on properties such as model size and the number of examples, highlighting that robust task adaptation remains a challenge.

Summary Notes

Comparing Few-shot Fine-tuning and In-context Learning: A Balanced Evaluation

In the rapidly evolving field of Natural Language Processing (NLP), leveraging pre-trained language models for specific tasks has become crucial. The strategies of few-shot fine-tuning (FT) and in-context learning (ICL) are particularly notable for their efficiency and effectiveness.

Yet, discussions about which method is superior have often been clouded by unequal experimental setups. This post aims to offer a fair comparison between FT and ICL, with a focus on their use in enterprise environments by AI engineers.

Understanding Task Adaptation in NLP

Pre-trained language models have revolutionized NLP by learning from extensive text data, which can then be fine-tuned for specific tasks with smaller datasets.

Task adaptation is vital for customizing general models for specific needs. Among the adaptation methods, few-shot fine-tuning and in-context learning are predominant. However, their direct comparison has been hampered by unequal testing conditions in past research.

Fair Comparison Methodology

For a balanced evaluation, we:

• Used the same model architecture (OPT) across sizes from 125M to 30B parameters for both FT and ICL.
• Kept the number of examples consistent and controlled other variables to ensure differences in performance were due to the adaptation method, not external factors.

Performance Insights

Our analysis showed that under similar conditions, FT and ICL have comparable generalization abilities. Yet, their performance can vary greatly depending on model size and dataset size. Notably, FT often surpasses ICL in tasks with out-of-domain data, suggesting it's more resilient when the task differs significantly from the model's pre-training data.

Pros and Cons

• In-context Learning (ICL): ICL shines in its simplicity and flexibility. It allows for quick task adaptation through natural language prompts, making it ideal for situations where speed and ease of use are paramount.
• Few-shot Fine-tuning (FT): FT provides more stable and consistent performance across various tasks and datasets. Though it requires more time and computational resources than ICL, the investment typically results in better performance, especially for complex or out-of-domain tasks.

Choosing between FT and ICL depends on the task's specific needs and available resources. ICL is preferable for tasks closely aligned with the pre-training data and requiring fast adaptation. For more complex tasks or those significantly different from the pre-training data, FT is likely a better choice.

Embracing a Balanced View

This comparison highlights the need for controlled evaluations in identifying the most effective NLP task adaptation methods. Both FT and ICL have strengths and weaknesses that can complement each other depending on the application. Understanding their unique advantages allows AI engineers in enterprise settings to make informed decisions, leading to more efficient and effective NLP applications.

Key Insights for AI Engineers:

• Fair Comparison: Always compare adaptation methods under similar conditions for accurate conclusions.
• Task Requirements: The choice between FT and ICL should consider the task's specific needs, including how closely it aligns with the pre-training data and the urgency of adaptation.
• Resource Consideration: Factor in the available computational resources and time, as FT usually demands more than ICL.
• Strategy Selection: Recognize that both FT and ICL are valuable tools in the NLP toolkit, with the optimal choice often hinging on a balance of task complexity, domain specificity, and resource availability.

Staying updated on the latest NLP methods and their applications is essential for AI engineers. By making well-informed decisions about task adaptation strategies, we can continue to advance the capabilities of language models, driving innovation and efficiency in enterprise applications.