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Conformal Prediction for Large Language Models Without Logit-Access


Core Concepts
This study introduces a novel Conformal Prediction method tailored for API-only Large Language Models without logit-access, ensuring efficient prediction sets with a statistical coverage guarantee.
Abstract

The study addresses the challenge of quantifying uncertainty in Large Language Models (LLMs) without logit-access. It proposes a novel Conformal Prediction method that leverages coarse-grained and fine-grained uncertainty notions to improve efficiency and accuracy in predicting responses. Experimental results demonstrate the effectiveness of the approach in outperforming logit-based baselines across various tasks.

Key points:

  • Addressing uncertainty quantification challenges in Large Language Models (LLMs) without logit-access.
  • Introducing a novel Conformal Prediction method tailored for API-only LLMs.
  • Leveraging frequency as a coarse-grained measure and introducing fine-grained notions like NE and SS to enhance prediction efficiency.
  • Demonstrating superior performance over logit-based methods through experiments on open-ended and close-ended Question Answering tasks.
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Stats
A minimum of 9,604 samples is required to achieve a 95% confidence level with a 1% margin of error. The proposed nonconformity score function combines frequency, NE, and SS measures to enhance uncertainty estimation. The method ensures rigorous statistical coverage guarantees without relying on model logits.
Quotes
"Our proposed approach does not rely on model logits and can alleviate the known miscalibration issue when using logits." "Experiments demonstrate the superior performance of our approach compared to logit-based and logit-free baselines."

Key Insights Distilled From

by Jiayuan Su,J... at arxiv.org 03-05-2024

https://arxiv.org/pdf/2403.01216.pdf
API Is Enough

Deeper Inquiries

How can the proposed Conformal Prediction method be adapted for other types of language models beyond APIs?

The proposed Conformal Prediction (CP) method can be adapted for other types of language models beyond APIs by following a similar approach to handle uncertainty estimation. One key aspect is to define nonconformity measures using different sources of uncertainty information, as done in the proposed method. This could involve leveraging various aspects such as response frequency, normalized entropy, and semantic similarity to capture both coarse-grained and fine-grained uncertainties. To adapt this method for other language models, researchers would need to understand the specific characteristics and limitations of those models. They would then need to tailor the nonconformity score function based on these characteristics while ensuring that it remains model-agnostic and distribution-free. Additionally, adapting the sampling strategy and hyperparameter configuration according to the nature of the new language model is crucial for effective implementation. Overall, adapting the CP method for different types of language models involves customizing the approach based on each model's unique features while maintaining a focus on robust uncertainty quantification without direct access to internal model information.

What are the potential implications of reducing reliance on logits for uncertainty estimation in Large Language Models?

Reducing reliance on logits for uncertainty estimation in Large Language Models (LLMs) can have several significant implications: Improved Robustness: By moving away from relying solely on logits which may suffer from miscalibration issues or overconfidence problems, uncertainty estimation becomes more robust and reliable. Enhanced Generalization: Logits provide limited insight into uncertain regions where LLMs may struggle; incorporating alternative sources like response frequency or semantic similarity allows for better generalization across diverse data distributions. Responsible AI Applications: Uncertainty estimates play a crucial role in responsible AI applications by providing insights into when an LLM might produce unreliable outputs or "hallucinate." Reducing reliance on potentially flawed logit-based estimations enhances trustworthiness in AI systems. Scalability: Moving towards methods that do not require direct access to internal model information like logits increases scalability since it eliminates dependencies on specific internal structures or mechanisms within LLMs. In essence, reducing dependence on logits leads to more accurate uncertainty quantification in LLMs, promoting reliability and trustworthiness in their applications across various domains.

How might incorporating fine-grained uncertainty notions impact the scalability of the proposed approach?

Incorporating fine-grained uncertainty notions such as normalized entropy (NE) and semantic similarity (SS) alongside coarse-grained measures like response frequency can impact scalability positively by enhancing efficiency while maintaining accuracy: Efficient Differentiation: Fine-grained notions help distinguish between responses with similar coarse-grained scores but varying levels of certainty due to NE capturing prompt-wise consistency and SS measuring response-wise similarity. Optimized Prediction Sets: By considering both coarse- and fine-grained uncertainties together, prediction sets become more precise with reduced redundancy or overlap among responses sharing similar frequencies. Reduced Computational Complexity: Despite introducing additional complexity through fine-grained measures, optimizing algorithms around NE and SS ensures computational efficiency by focusing efforts where they matter most—on responses requiring nuanced distinctions rather than exhaustive calculations across all possibilities. Enhanced Scalability Across Diverse Data Distributions: The incorporation of fine-grained uncertainties enables better adaptation to varied data distributions without compromising performance or increasing computational overhead significantly. Therefore, integrating fine-grain uncertainties into CP methods improves their effectiveness without sacrificing scalability—a critical factor when deploying solutions at scale across different contexts within NLP tasks involving large language models like those discussed in this study.
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