核心概念
Pretrained large language models can effectively serve as OOD proxies, and the likelihood ratio between a pretrained LLM and its finetuned variant provides a powerful criterion for detecting out-of-distribution data.
摘要
The paper revisits the use of the likelihood ratio between a pretrained large language model (LLM) and its finetuned variant as a criterion for out-of-distribution (OOD) detection. The key insights are:
- Pretrained LLMs can function as effective OOD proxies, as they encompass broad knowledge about language and can distinguish in-distribution data from OOD data.
- Calculating the likelihood ratio between the pretrained LLM and its finetuned counterpart serves as a robust OOD detection criterion, leveraging the prior knowledge in the base model and the specialized knowledge in the finetuned model.
- This approach is particularly convenient as practitioners often already have access to both the pretrained and finetuned LLMs, eliminating the need for additional training.
- The authors evaluate the method across various scenarios, including far OOD, near OOD, spam detection, and question-answering (QA) systems. The results demonstrate the effectiveness of the likelihood ratio in identifying OOD instances.
- For QA systems, the authors propose a novel approach that generates an answer using the finetuned LLM and then applies the likelihood ratio criterion to the question-answer pair, leading to improved OOD question detection.
統計資料
The ducks in Janet's farm lay 16 eggs per day.
Janet eats 3 eggs for breakfast every morning.
Janet bakes muffins for her friends every day using 4 eggs.
Janet sells the remaining fresh duck eggs at the farmers' market for $2 per egg.
引述
"Guided by this insight, we discover that the likelihood ratio between the base model and its finetuned counterpart serves as an effective criterion for detecting OOD data."
"Leveraging the power of LLMs, we show that, for the first time, the likelihood ratio can serve as an effective OOD detector."