Value Augmented Sampling for Language Model Alignment and Personalization
This addresses the need for practical and stable alignment methods for LLMs, enabling personalization and safety without high computational costs or access to model weights, though it is an incremental improvement over existing RL and search-based approaches.
The paper tackles the problem of aligning large language models to human preferences efficiently by introducing Value Augmented Sampling (VAS), a framework that maximizes rewards using only data from a frozen LLM, achieving comparable results to Best-of-128 with lower inference cost and outperforming PPO and DPO on standard benchmarks.
Aligning Large Language Models (LLMs) to cater to different human preferences, learning new skills, and unlearning harmful behavior is an important problem. Search-based methods, such as Best-of-N or Monte-Carlo Tree Search, are performant, but impractical for LLM adaptation due to their high inference cost. On the other hand, using Reinforcement Learning (RL) for adaptation is computationally efficient, but performs worse due to the optimization challenges in co-training the value function and the policy. We present a new framework for reward optimization, Value Augmented Sampling (VAS), that can maximize different reward functions using data sampled from only the initial, frozen LLM. VAS solves for the optimal reward-maximizing policy without co-training the policy and the value function, making the optimization stable, outperforming established baselines, such as PPO and DPO, on standard benchmarks, and achieving comparable results to Best-of-128 with lower inference cost. Unlike existing RL methods that require changing the weights of the LLM, VAS does not require access to the weights of the pre-trained LLM. Thus, it can even adapt LLMs (e.g., ChatGPT), which are available only as APIs. In addition, our algorithm unlocks the new capability of composing several rewards and controlling the extent of each one during deployment time, paving the road ahead for the future of aligned, personalized LLMs.