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While Direct Preference Optimization (DPO) has become the de facto approach for aligning Large Vision-Language Models (LVLMs), it suffers from Likelihood Displacement, where the probability of both chosen and rejected responses collapses.…

Computer Vision and Pattern Recognition · Computer Science 2026-03-24 Kaili Huang , Hongming Zhang , Rui Shen , Linjun Dai , Jiahao Wang , Hanming Deng , Lewei Lu

Direct Preference Optimization (DPO) and its variants have become increasingly popular for aligning language models with human preferences. These methods aim to teach models to better distinguish between chosen (or preferred) and rejected…

Computation and Language · Computer Science 2025-06-09 Xiliang Yang , Feng Jiang , Qianen Zhang , Lei Zhao , Xiao Li

Multi-Objective Alignment (MOA) aims to align LLMs' responses with multiple human preference objectives, with Direct Preference Optimization (DPO) emerging as a prominent approach. However, we find that DPO-based MOA approaches suffer from…

Machine Learning · Computer Science 2025-12-09 Moxin Li , Yuantao Zhang , Wenjie Wang , Wentao Shi , Zhuo Liu , Fuli Feng , Tat-Seng Chua

Direct Preference Optimization (DPO) and its variants have become standard for aligning Large Language Models due to their simplicity and offline stability. However, we identify two fundamental limitations. First, the optimal policy depends…

Artificial Intelligence · Computer Science 2026-02-10 Yu Li , Tian Lan , Zhengling Qi

Reinforcement learning from human feedback (RLHF) has demonstrated great promise in aligning large language models (LLMs) with human preference. Depending on the availability of preference data, both online and offline RLHF are active areas…

Machine Learning · Computer Science 2025-02-20 Shicong Cen , Jincheng Mei , Katayoon Goshvadi , Hanjun Dai , Tong Yang , Sherry Yang , Dale Schuurmans , Yuejie Chi , Bo Dai

As Large Language Models (LLMs) are increasingly deployed in real-world applications, balancing helpfulness and safety has become a central challenge. A natural approach is to incorporate safety constraints into Reinforcement Learning from…

Machine Learning · Computer Science 2026-03-05 Geon-Hyeong Kim , Yu Jin Kim , Byoungjip Kim , Honglak Lee , Kyunghoon Bae , Youngsoo Jang , Moontae Lee

Generative AI can now synthesize strikingly realistic images from text, yet output quality remains highly sensitive to how prompts are phrased. Direct Preference Optimization (DPO) offers a lightweight, off-policy alternative to RL for…

Computation and Language · Computer Science 2025-07-30 Anas Mohamed , Azal Ahmad Khan , Xinran Wang , Ahmad Faraz Khan , Shuwen Ge , Saman Bahzad Khan , Ayaan Ahmad , Ali Anwar

Preference optimization is widely used to align Large Language Models (LLMs) with preference feedback. However, most existing methods train on a single positive-negative pair per prompt, discarding additional supervision available in…

Computation and Language · Computer Science 2026-04-20 Jixuan Leng , Si Si , Hsiang-Fu Yu , Vinod Raman , Inderjit S. Dhillon

Existing training-time safety alignment techniques for large language models (LLMs) remain vulnerable to jailbreak attacks. Direct preference optimization (DPO), a widely deployed alignment method, exhibits limitations in both experimental…

Computation and Language · Computer Science 2025-10-31 Xuandong Zhao , Will Cai , Tianneng Shi , David Huang , Licong Lin , Song Mei , Dawn Song

The recent success in using human preferences to align large language models (LLMs) has significantly improved their performance in various downstream tasks, such as question answering, mathematical reasoning, and code generation. However,…

Machine Learning · Computer Science 2026-05-18 Xiaoqiang Lin , Arun Verma , Zhongxiang Dai , Daniela Rus , See-Kiong Ng , Bryan Kian Hsiang Low

Reinforcement learning (RL) has become a cornerstone for fine-tuning Large Language Models (LLMs), with Proximal Policy Optimization (PPO) serving as the de facto standard algorithm. Despite its ubiquity, we argue that the core ratio…

Machine Learning · Computer Science 2026-05-27 Penghui Qi , Xiangxin Zhou , Zichen Liu , Tianyu Pang , Chao Du , Min Lin , Wee Sun Lee

Aligning language models (LMs) with curated human feedback is critical to control their behaviors in real-world applications. Several recent policy optimization methods, such as DPO and SLiC, serve as promising alternatives to the…

Computation and Language · Computer Science 2025-01-28 Tianqi Liu , Zhen Qin , Junru Wu , Jiaming Shen , Misha Khalman , Rishabh Joshi , Yao Zhao , Mohammad Saleh , Simon Baumgartner , Jialu Liu , Peter J. Liu , Xuanhui Wang

Direct Preference Optimization (DPO) has recently emerged as a simple and effective alternative to reinforcement learning from human feedback (RLHF) for aligning large language models (LLMs) with user preferences. However, existing DPO…

Machine Learning · Computer Science 2025-10-10 Jason Bohne , Pawel Polak , David Rosenberg , Brian Bloniarz , Gary Kazantsev

Reinforcement Learning with Human Feedback (RLHF) and its variants have made huge strides toward the effective alignment of large language models (LLMs) to follow instructions and reflect human values. More recently, Direct Alignment…

Computation and Language · Computer Science 2025-06-02 Aman Gupta , Shao Tang , Qingquan Song , Sirou Zhu , Jiwoo Hong , Ankan Saha , Viral Gupta , Noah Lee , Eunki Kim , Siyu Zhu , Parag Agrawal , Natesh Pillai , S. Sathiya Keerthi

Direct Preference Optimization (DPO) and related methods align large language models from pairwise preferences by regularizing updates against a fixed reference policy. As the policy drifts, a static reference, however, can become…

Machine Learning · Computer Science 2026-05-18 Youngjae Cho , Jongsuk Kim , Ji-Hoon Kim

Using reinforcement learning with human feedback (RLHF) has shown significant promise in fine-tuning diffusion models. Previous methods start by training a reward model that aligns with human preferences, then leverage RL techniques to…

Machine Learning · Computer Science 2024-03-26 Kai Yang , Jian Tao , Jiafei Lyu , Chunjiang Ge , Jiaxin Chen , Qimai Li , Weihan Shen , Xiaolong Zhu , Xiu Li

Reinforcement learning from human feedback (RLHF) has been popular for aligning text-to-image (T2I) diffusion models with human preferences. As a mainstream branch of RLHF, Direct Preference Optimization (DPO) offers a computationally…

Machine Learning · Computer Science 2026-05-07 Jiaming Hu , Jiamu Bai , Haoyu Wang , Debarghya Mukherjee , Ioannis Ch. Paschalidis

The task adaptation and alignment of Large Multimodal Models (LMMs) have been significantly advanced by instruction tuning and further strengthened by recent preference optimization. Yet, most LMMs still suffer from severe modality…

Machine Learning · Computer Science 2025-10-10 Chenxi Liu , Tianyi Xiong , Yanshuo Chen , Ruibo Chen , Yihan Wu , Junfeng Guo , Tianyi Zhou , Heng Huang

Mathematical reasoning presents a significant challenge for Large Language Models (LLMs) as it requires ensuring the correctness of each reasoning step. Researchers have been strengthening the mathematical reasoning abilities of LLMs…

Machine Learning · Computer Science 2025-06-23 Yunze Lin

As the era of large language models (LLMs) unfolds, Preference Optimization (PO) methods have become a central approach to aligning LLMs with human preferences and improving performance. We propose Maximum a Posteriori Preference…