Direct Preference Optimization Using Sparse Feature-Level Constraints
Authors: name: Qingyu Yin, name: Chak Tou Leong, name: Hongbo Zhang, name: Minjun Zhu, name: Hanqi Yan, name: Qiang Zhang, name: Yulan He, name: Wenjie Li, name: Jun Wang, name: Yue Zhang, name: Linyi Yang

The alignment of large language models (LLMs) with human preferences remains
a key challenge. While post-training techniques like Reinforcement Learning
from Human Feedback (RLHF) and Direct Preference Optimization (DPO) have
achieved notable success, they often introduce computational inefficiencies and
training instability. In this paper, we propose Feature-level constrained
Preference Optimization (FPO), a novel method designed to simplify the
alignment process while ensuring stability. FPO leverages pre-trained Sparse
Autoencoders (SAEs) and introduces feature-level constraints, allowing for
efficient, sparsity-enforced alignment. Our approach enjoys efficiency by using
sparse features activated in a well-trained sparse autoencoder and the quality
of sequential KL divergence by using the feature-level offline reference.
Experimental results on benchmark datasets demonstrate that FPO achieves a
5.08% absolute improvement in win rate with much lower computational cost
compared to state-of-the-art baselines, making it a promising solution for
efficient and controllable LLM alignments.