BPO: Towards Balanced Preference Optimization between Knowledge Breadth and Depth in Alignment
This addresses a specific data imbalance problem in LLM alignment tuning, offering incremental improvements for researchers and practitioners in the field.
The paper tackles the imbalance between knowledge breadth and depth in alignment tuning datasets for large language models, showing that balancing prompts and responses improves performance, and proposes Balanced Preference Optimization (BPO) to dynamically augment knowledge depth, achieving better results than baselines across benchmarks.
Reinforcement Learning with Human Feedback (RLHF) is the key to the success of large language models (LLMs) in recent years. In this work, we first introduce the concepts of knowledge breadth and knowledge depth, which measure the comprehensiveness and depth of an LLM or knowledge source respectively. We reveal that the imbalance in the number of prompts and responses can lead to a potential disparity in breadth and depth learning within alignment tuning datasets by showing that even a simple uniform method for balancing the number of instructions and responses can lead to significant improvements. Building on this, we further propose Balanced Preference Optimization (BPO), designed to dynamically augment the knowledge depth of each sample. BPO is motivated by the observation that the usefulness of knowledge varies across samples, necessitating tailored learning of knowledge depth. To achieve this, we introduce gradient-based clustering, estimating the knowledge informativeness and usefulness of each augmented sample based on the model's optimization direction. Our experimental results across various benchmarks demonstrate that BPO outperforms other baseline methods in alignment tuning while maintaining training efficiency. Furthermore, we conduct a detailed analysis of each component of BPO, providing guidelines for future research in preference data optimization.