RRHF: Rank Responses to Align Language Models with Human Feedback without tears

TL;DR

RRHF introduces a simplified, efficient method for aligning large language models with human preferences by ranking responses based on conditional probabilities, reducing complexity and hyperparameter sensitivity compared to PPO.

Contribution

The paper proposes RRHF, a novel ranking-based learning paradigm that simplifies and improves the process of aligning language models with human feedback, requiring fewer models and less hyperparameter tuning.

Findings

RRHF achieves comparable performance to PPO in alignment tasks.

RRHF requires only 1-2 models during tuning, simplifying implementation.

Performance depends heavily on sampling quality, indicating a best-of-n learning approach.

Abstract

Reinforcement Learning from Human Feedback (RLHF) facilitates the alignment of large language models with human preferences, significantly enhancing the quality of interactions between humans and models. InstructGPT implements RLHF through several stages, including Supervised Fine-Tuning (SFT), reward model training, and Proximal Policy Optimization (PPO). However, PPO is sensitive to hyperparameters and requires multiple models in its standard implementation, making it hard to train and scale up to larger parameter counts. In contrast, we propose a novel learning paradigm called RRHF, which scores sampled responses from different sources via a logarithm of conditional probabilities and learns to align these probabilities with human preferences through ranking loss. RRHF can leverage sampled responses from various sources including the model responses from itself, other large language model responses, and human expert responses to learn to rank them. RRHF only needs 1 to 2 models during tuning and can efficiently align language models with human preferences robustly without complex hyperparameter tuning. Additionally, RRHF can be considered an extension of SFT and reward model training while being simpler than PPO in terms of coding, model counts, and hyperparameters. We evaluate RRHF on the Helpful and Harmless dataset, demonstrating comparable alignment performance with PPO by reward model score and human labeling. Extensive experiments show that the performance of RRHF is highly related to sampling quality which suggests RRHF is a best-of-n learner. Codes available at https://github.com/GanjinZero/RRHF.