Original Paper: https://arxiv.org/abs/2309.17249

By: Han Zhou, Xingchen Wan, Lev Proleev, Diana Mincu, Jilin Chen, Katherine Heller, Subhrajit Roy

Abstract:

Prompting and in-context learning (ICL) have become efficient learning paradigms for large language models (LLMs). However, LLMs suffer from prompt brittleness and various bias factors in the prompt, including but not limited to the formatting, the choice verbalizers, and the ICL examples. To address this problem that results in unexpected performance degradation, calibration methods have been developed to mitigate the effects of these biases while recovering LLM performance. In this work, we first conduct a systematic analysis of the existing calibration methods, where we both provide a unified view and reveal the failure cases. Inspired by these analyses, we propose Batch Calibration (BC), a simple yet intuitive method that controls the contextual bias from the batched input, unifies various prior approaches, and effectively addresses the aforementioned issues. BC is zero-shot, inference-only, and incurs negligible additional costs. In the few-shot setup, we further extend BC to allow it to learn the contextual bias from labeled data. We validate the effectiveness of BC with PaLM 2-(S, M, L) and CLIP models and demonstrate state-of-the-art performance over previous calibration baselines across more than 10 natural language understanding and image classification tasks.

Summary Notes

Enhancing Large Language Model Performance with Batch Calibration

Large Language Models (LLMs) like PaLM 2 and CLIP are changing the game in artificial intelligence, thanks to their ability to learn and adapt through prompting and in-context learning (ICL).

These techniques enable LLMs to process and respond to input examples in a flexible manner, eliminating the need for continuous retraining for different tasks.

However, their performance can be unpredictable due to their sensitivity to the specifics of the prompts, such as wording, format, and the sequence of inputs. This presents a reliability challenge for AI engineers in enterprise environments.

The Issue with Prompt Sensitivity

• Impact of Prompt Design: LLM efficiency is hindered by their prompt sensitivity, leading to variable performance based on how prompts are designed.
• Prediction Biases: Prompts can introduce biases, affecting the trustworthiness of model outputs.
• Calibration Challenges: Traditional calibration methods often don't fully address these biases, especially in complex or new scenarios.

Introducing Batch Calibration

To overcome these challenges, a new strategy called Batch Calibration (BC) has been developed.

BC is noteworthy because it effectively manages the biases from prompt designs without needing labeled data, making it ideal for zero-shot scenarios.

It works by averaging the model's scores across a batch of inputs to estimate bias, then adjusting these scores based on that average.

How Batch Calibration Works

• Estimating Bias: BC determines the average bias across a batch of inputs to set a baseline for adjustments.
• Adjusting Without Labeled Data: BC is beneficial in situations where labeled data is scarce or unavailable.
• Enhancements with BCL: With access to labeled data, BC can be upgraded to BCL for improved bias estimation and accuracy.

Proven Effectiveness

Testing on over 10 natural language processing tasks and various image classification tasks has proven BC's effectiveness:

• Superior Performance: BC has consistently outperformed baseline methods, proving its robustness.
• Flexible Application: Its success across different models and tasks showcases BC's wide applicability.
• Consistency Amidst Prompt Changes: BC remains effective even with significant prompt variations, ensuring reliability.

Implications for AI Engineers

Batch Calibration offers a valuable solution for AI engineers facing the challenge of prompt sensitivity in LLMs. Its capability to adjust for biases in predictions without labeled data is particularly advantageous in data-scarce scenarios.

BC's versatility and reliability across tasks and models also highlight its potential as an essential tool in LLM deployment.

Future Directions

Looking forward, expanding Batch Calibration's applications to generative tasks and other areas, along with further enhancements using labeled data, are key focuses. These efforts aim to broaden BC's utility and improve its precision, reinforcing its importance for AI engineers working with LLMs.

Acknowledgements

The development of Batch Calibration is a joint effort, with significant contributions from the teams at Google Research and the University of Cambridge.

Their work continues to push the boundaries of AI and machine learning, offering solutions to some of the most critical challenges in the field.

In summary, Batch Calibration marks a crucial advancement in managing the prompt sensitivity of LLMs, offering a practical and efficient approach that could transform their deployment in various industries.

By overcoming the limitations of existing calibration techniques, BC opens the door to more dependable and flexible uses of LLMs across a multitude of tasks and sectors.