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arxiv_cl 95% Match Research Paper ML Researchers,AI Alignment Researchers,NLP Engineers,Developers of LLMs 17 hours ago

On Extending Direct Preference Optimization to Accommodate Ties

large-language-models › alignment
📄 Abstract

Abstract: We derive and investigate two DPO variants that explicitly model the possibility of declaring a tie in pair-wise comparisons. We replace the Bradley-Terry model in DPO with two well-known modeling extensions, by Rao and Kupper and by Davidson, that assign probability to ties as alternatives to clear preferences. Our experiments in neural machine translation and summarization show that explicitly labeled ties can be added to the datasets for these DPO variants without the degradation in task performance that is observed when the same tied pairs are presented to DPO. We find empirically that the inclusion of ties leads to stronger regularization with respect to the reference policy as measured by KL divergence, and we see this even for DPO in its original form. We provide a theoretical explanation for this regularization effect using ideal DPO policy theory. We further show performance improvements over DPO in translation and mathematical reasoning using our DPO variants. We find it can be beneficial to include ties in preference optimization rather than simply discard them, as is done in common practice.

Key Contributions

This paper introduces two variants of Direct Preference Optimization (DPO) that explicitly model ties in pairwise comparisons, using extensions to the Bradley-Terry model. Experiments show these variants improve performance in NMT and summarization, provide stronger regularization, and offer theoretical explanations for this effect, outperforming standard DPO in translation and mathematical reasoning.

Business Value

Enables more robust and accurate alignment of LLMs with human preferences, leading to better-performing and more reliable AI systems for various applications.