arXiv Machine Learning
Aug 28

Disentangling Optimization Scale from Preference Scale in DPO

The paper investigates the Direct Preference Optimization (DPO) objective used for aligning language models, revealing that its coefficient β simultaneously controls both the inverse preference-noise scale and the optimization dynamics. This entanglement causes non‑monotonic policy deviation with respect to β and makes loss values incomparable across different β settings. The authors propose a centered‑softplus reformulation that decouples these effects, allowing independent tuning of the noise scale and learning‑rate, and provides a smooth β←0 limit that reduces to a linear preference‑margin objective.

By Ivan Kruzhilov
arXiv AI
2d ago

Gradient-Aligned Pair Selection for Personalized Preference Optimization

The paper introduces GAP-DPO, a method for personalizing large language models by selecting preference pairs based on gradient alignment with user utility. It formalizes personalized preference learning as a geometry‑aligned optimization problem, showing that off‑policy sampling can shift DPO updates from error correction to reinforcement when preference margins align with utility gradients. Experiments demonstrate that GAP‑DPO improves stylistic fidelity, preference alignment, and overall generation quality over standard DPO variants.

By Ruoming Jin, Xinyu Li, Hao Zhou, Jianfeng Zhu, Ruixin Guo, Feodor Dragan, Lei Xu, Haixun Wang, Yang Zhou