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Aligning large language models (LLMs) with human preferences is a critical challenge in AI research. While methods like Reinforcement Learning from Human Feedback (RLHF) and Direct Preference Optimization (DPO) are widely used, they often…

Computation and Language · Computer Science 2026-05-19 Xuan Qi , Rongwu Xu , Zhijing Jin

Direct Preference Optimization (DPO) has been proposed as a promising alternative to Proximal Policy Optimization (PPO) based Reinforcement Learning with Human Feedback (RLHF). However, empirical evaluations consistently reveal suboptimal…

Machine Learning · Computer Science 2025-03-03 Qinwei Ma , Jingzhe Shi , Can Jin , Jenq-Neng Hwang , Serge Belongie , Lei Li

Inference-time alignment provides an efficient alternative for aligning LLMs with humans. However, these approaches still face challenges, such as limited scalability due to policy-specific value functions and latency during the inference…

Computation and Language · Computer Science 2025-05-27 Ruizhe Chen , Wenhao Chai , Zhifei Yang , Xiaotian Zhang , Joey Tianyi Zhou , Tony Quek , Soujanya Poria , Zuozhu Liu

Direct Preference Optimization (DPO) controls the trade-off between fitting preference labels and staying close to a reference model using a single global temperature beta, implicitly treating all preference pairs as equally informative.…

Computation and Language · Computer Science 2026-02-02 Chaoyue He , Xin Zhou , Di Wang , Hong Xu , Wei Liu , Chunyan Miao

Diffusion policies, widely adopted in decision-making scenarios such as robotics, gaming and autonomous driving, are capable of learning diverse skills from demonstration data due to their high representation power. However, the sub-optimal…

Machine Learning · Computer Science 2025-09-30 Ningyuan Yang , Jiaxuan Gao , Feng Gao , Yi Wu , Chao Yu

Preference optimization is crucial for aligning large language models (LLMs) with human values and intentions. A significant challenge in this process is the distribution mismatch between pre-collected offline preference data and the…

Computation and Language · Computer Science 2026-03-02 Junming Yang , Ning Xu , Biao Liu , Shiqi Qiao , Xin Geng

Diffusion policies excel at robotic manipulation by naturally modeling multimodal action distributions in high-dimensional spaces. Nevertheless, diffusion policies suffer from diffusion representation collapse: semantically similar…

Artificial Intelligence · Computer Science 2026-04-23 Guowei Zou , Weibing Li , Hejun Wu , Yukun Qian , Yuhang Wang , Haitao Wang

Direct Preference Optimization (DPO) is an effective approach for aligning protein language models with experimental design goals. However, DPO faces a scalability bottleneck: the number of possible training pairs grows quadratically with…

Machine Learning · Computer Science 2025-11-27 Constance Ferragu , Jonathan D. Ziegler , Nicolas Deutschmann , Arthur Lindoulsi , Eli Bixby , Cradle ML Team

Proximal Policy Optimization (PPO) is a popular model-free reinforcement learning algorithm, esteemed for its simplicity and efficacy. However, due to its inherent on-policy nature, its proficiency in harnessing data from disparate policies…

Machine Learning · Computer Science 2024-06-07 Yaozhong Gan , Renye Yan , Xiaoyang Tan , Zhe Wu , Junliang Xing

Reinforcement Learning (RL) algorithms for safety alignment of Large Language Models (LLMs), such as Direct Preference Optimization (DPO), encounter the challenge of distribution shift. Current approaches typically address this issue…

Computation and Language · Computer Science 2025-06-17 Qiyuan Deng , Xuefeng Bai , Kehai Chen , Yaowei Wang , Liqiang Nie , Min Zhang

DPO (Direct Preference Optimization) has become a widely used offline preference optimization algorithm due to its simplicity and training stability. However, DPO is prone to overfitting and collapse. To address these challenges, we propose…

Machine Learning · Computer Science 2025-08-26 Rui Wang , Qianguo Sun , Chao Song , Junlong Wu , Tianrong Chen , Zhiyun Zeng , Yu Li

Diffusion Models have revolutionized the field of human motion generation by offering exceptional generation quality and fine-grained controllability through natural language conditioning. Their inherent stochasticity, that is the ability…

Computer Vision and Pattern Recognition · Computer Science 2024-05-08 Massimiliano Pappa , Luca Collorone , Giovanni Ficarra , Indro Spinelli , Fabio Galasso

Preference optimization is a critical post-training technique used to align large language models (LLMs) with human preferences, typically by fine-tuning on ranked response pairs. While methods like Direct Preference Optimization (DPO) have…

Computation and Language · Computer Science 2025-11-12 Rhitabrat Pokharel , Yufei Tao , Ameeta Agrawal

In recent years, the field of image generation has witnessed significant advancements, particularly in fine-tuning methods that align models with universal human preferences. This paper explores the critical role of preference data in the…

Computer Vision and Pattern Recognition · Computer Science 2025-03-24 Lingfan Zhang , Chen Liu , Chengming Xu , Kai Hu , Donghao Luo , Chengjie Wang , Yanwei Fu , Yuan Yao

Policy-based Reinforcement Learning (RL) has established itself as the dominant paradigm in generative recommendation for optimizing sequential user interactions. However, when applied to offline historical logs, these methods suffer a…

Machine Learning · Computer Science 2026-02-12 Jie Jiang , Yusen Huo , Xiangxin Zhan , Changping Wang , Jun Zhang

The application of diffusion models in 3D LiDAR scene completion is limited due to diffusion's slow sampling speed. Score distillation accelerates diffusion sampling but with performance degradation, while post-training with direct policy…

Computer Vision and Pattern Recognition · Computer Science 2025-04-17 An Zhao , Shengyuan Zhang , Ling Yang , Zejian Li , Jiale Wu , Haoran Xu , AnYang Wei , Perry Pengyun GU , Lingyun Sun

Direct Preference Optimization (DPO) has become the de facto standard for offline preference alignment of large language models, but its reliance on a reference policy introduces a critical tension. DPO weighs each update relative to a…

Machine Learning · Computer Science 2026-02-13 Suqin Yuan , Xingrui Yu , Jiyang Zheng , Lei Feng , Dadong Wang , Ivor Tsang , Tongliang Liu

Flow-based generative models, including diffusion models, excel at modeling continuous distributions in high-dimensional spaces. In this work, we introduce Flow Policy Optimization (FPO), a simple on-policy reinforcement learning algorithm…

Machine Learning · Computer Science 2025-08-04 David McAllister , Songwei Ge , Brent Yi , Chung Min Kim , Ethan Weber , Hongsuk Choi , Haiwen Feng , Angjoo Kanazawa

Direct Preference Optimization (DPO) is a widely used RL-free method for aligning language models from pairwise preferences, but it models preferences over full sequences even though generation is driven by per-token decisions. Existing…

Computation and Language · Computer Science 2026-05-15 Truong Nguyen , Tien-Phat Nguyen , Linh Ngo Van , Duy Minh Ho Nguyen , Khoa D. Doan , Trung Le

Direct Preference Optimization (DPO) is broadly utilized for aligning Large Language Models (LLMs) with human values because of its flexibility. Despite its effectiveness, it has been observed that the capability of DPO to generate…

Machine Learning · Computer Science 2025-05-20 Wenqiao Zhu , Ji Liu , Lulu Wang , Jun Wu , Yulun Zhang