Self-Consistency Preference Optimization
Authors: name: Archiki Prasad, name: Weizhe Yuan, name: Richard Yuanzhe Pang, name: Jing Xu, name: Maryam Fazel-Zarandi, name: Mohit Bansal, name: Sainbayar Sukhbaatar, name: Jason Weston, name: Jane Yu

Self-alignment, whereby models learn to improve themselves without human
annotation, is a rapidly growing research area. However, existing techniques
often fail to improve complex reasoning tasks due to the difficulty of
assigning correct rewards. An orthogonal approach that is known to improve
correctness is self-consistency, a method applied at inference time based on
multiple sampling in order to find the most consistent answer. In this work, we
extend the self-consistency concept to help train models. We thus introduce
self-consistency preference optimization (ScPO), which iteratively trains
consistent answers to be preferred over inconsistent ones on unsupervised new
problems. We show ScPO leads to large improvements over conventional reward
model training on reasoning tasks such as GSM8K and MATH, closing the gap with
supervised training with gold answers or preferences, and that combining ScPO
with standard supervised learning improves results even further. On ZebraLogic,
ScPO finetunes Llama-3 8B to be superior to Llama-3 70B, Gemma-2 27B, and
Claude-3 Haiku.