I am a research fellow at the Department of Mathematics, National University of Singapore. Previously, I obtained my PhD at NUS and I was previleged to be supervised by Prof. Vincent Y. F. Tan. Before that, I received my BS in Mathematics from Beijing Normal University, advised by Prof. Huajie Chen and Prof. Shihua Zhang.

Research

I am broadly interersted in both the theoretical limits and emprical applications of reinforcement learning and online learning (e.g., multi-armed bandits), with current emphasis on theoretically-guaranteed algorithmic design in Large Language Models. Feel free to reach out if you share similar interests!

I am currently seeking postdoctoral positions. Please feel free to reach out!

Theoretically-grounded Applications of Reinforcement Learning

• Development of practical and provably sound reinforcement learning methods for decision-making during model training and deployment.

Reinforcement Learning and Bandit Algorithm

• Characterization of fundamental limits of decision-making under practical modeling assumptions (e.g., stationary v.s. non-stationary, single- v.s. multi-agent), possibly subject to realistic constraints (e.g., efficiency or risk requirements).
• Design of provable algorithms that approach the fundamental performance limits.

News

• [2026-01] I PhinisheD my PhD study! Great thanks to the support from everyone, especially my supervisor Prof. Vincent Tan!
• [2026-01] Posted “Demystifying the Slash Pattern in Attention: The Role of RoPE”. We found RoPE is related to the emergence of slash patterns in attention matrices. Huge thanks to the amazing collaborators!
• [2025-12-22] Yunlong’s homepage was finally online! 🎉 Hello, world!