Distributionally Robust Direct Preference Optimization

• URL: http://arxiv.org/abs/2502.01930v1
• Date: Tue, 04 Feb 2025 02:03:19 GMT
• Title: Distributionally Robust Direct Preference Optimization
• Authors: Zaiyan Xu, Sushil Vemuri, Kishan Panaganti, Dileep Kalathil, Rahul Jain, Deepak Ramachandran,
• Abstract summary: A major challenge in aligning large language models with human preferences is the issue of distribution shift. We develop two novel distributionally robust direct preference optimization algorithms, namely, Wasserstein DPO (WDPO) and Kullback-Leibler DPO (KLDPO) Our empirical experiments demonstrate the superior performance of WDPO and KLDPO in substantially improving the alignment when there is a preference distribution shift.
• Score: 15.328510632723505
• License:
• Abstract: A major challenge in aligning large language models (LLMs) with human preferences is the issue of distribution shift. LLM alignment algorithms rely on static preference datasets, assuming that they accurately represent real-world user preferences. However, user preferences vary significantly across geographical regions, demographics, linguistic patterns, and evolving cultural trends. This preference distribution shift leads to catastrophic alignment failures in many real-world applications. We address this problem using the principled framework of distributionally robust optimization, and develop two novel distributionally robust direct preference optimization (DPO) algorithms, namely, Wasserstein DPO (WDPO) and Kullback-Leibler DPO (KLDPO). We characterize the sample complexity of learning the optimal policy parameters for WDPO and KLDPO. Moreover, we propose scalable gradient descent-style learning algorithms by developing suitable approximations for the challenging minimax loss functions of WDPO and KLDPO. Our empirical experiments demonstrate the superior performance of WDPO and KLDPO in substantially improving the alignment when there is a preference distribution shift.

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