  Reinforcement Learning from Human Feedback (RLHF) is a widely adopted
approach for aligning large language models with human values. However, RLHF
relies on a reward model that is trained with a limited amount of human
preference data, which could lead to inaccurate predictions. As a result, RLHF
may produce outputs that are misaligned with human values. To mitigate this
issue, we contribute a reward ensemble method that allows the reward model to
make more accurate predictions. As using an ensemble of large language
model-based reward models can be computationally and resource-expensive, we
explore efficient ensemble methods including linear-layer ensemble and
LoRA-based ensemble. Empirically, we run Best-of-$n$ and Proximal Policy
Optimization with our ensembled reward models, and verify that our ensemble
methods help improve the alignment performance of RLHF outputs.
