Dongyang Fan

Hi! Thanks for stopping by :) I'm a passionate 4th-year PhD student at Machine Learning and Optimization Lab at EPFL, supervised by Prof. Martin Jaggi. My name is pronounced as Don-Young.

My research interests include:

Data-Efficient Language Modeling
- Mixture-of-Experts architectures
- Decentralized training methods
- Accelerating LLM pretraining through metadata conditioning
Responsible Language Modeling
- Data-compliant pretraining by respecting owners’ opt-out choices.
- Designing compensation frameworks for data contributors
- Understanding and mitigating model hallucinations

I am also happy to branch out my research. If you want to reach out, do not hesitate to drop me an email!

Email / Google Scholar / Semantic Scholar / Twitter / Github / LinkedIn

Research

Note: WS denotes Workshop

preprint 2026	HalluHard: A Hard Multi-Turn Hallucination Benchmark Dongyang Fan, Sebastien Delsad, Nicolas Flammarion, Maksym Andriushchenko arXiv / code / website Hallucination Benchmark LLM Evaluation
ICLR 2026	Beyond URLs: Metadata Diversity and Position for Efficient LLM Pretraining Dongyang Fan, Diba Hashemi, Sai Praneeth Karimireddy, Martin Jaggi arXiv LLM Pretraining Metadata Data Efficiency
preprint 2025	Apertus: Democratizing Open and Compliant LLMs for Global Language Environments Apertus team (as a member of the pretraining team) arXiv Open LLMs Data Compliance Multilingual
COLM 2025 WS (oral 🏆)	TiMoE: Time-Aware Mixture of Language Experts Robin Faro, Dongyang Fan, Tamar Alphaidze, Martin Jaggi arXiv / codes / slides Mixture-of-Experts Temporal Modeling LLM Architecture
NeurIPS 2025	URLs Help, Topics Guide: Understanding Metadata Utility in LLM Training Dongyang Fan, Vinko Sabolčec, Martin Jaggi, arXiv / codes LLM Training Metadata Data Efficiency Steering
COLM 2025 (oral 🏆)	Can Performant LLMs Be Ethical? Quantifying the Impact of Web Crawling Opt-Outs Dongyang Fan, Vinko Sabolčec, Matin Ansaripour, Ayush Kumar Tarun, Martin Jaggi, Antoine Bosselut, Imanol Schlag arXiv / codes / project page / slides Data Compliance Ethics Memorization Responsible AI
ICLR WS 2025	Do Data Valuations Make Good Data Prices? Dongyang Fan, Tyler J. Rotello, Sai Praneeth Karimireddy arXiv Data Valuation Game Theory Data Markets
ICML 2025	On-Device Collaborative Language Modeling via a Mixture of Generalists and Specialists Dongyang Fan, Bettina Messmer, Nikita Doikov, Martin Jaggi codes / arXiv Collaborative Learning Mixture-of-Experts On-Device Federated Learning
ICLR WS 2024	Towards an empirical understanding of MoE design choices Dongyang Fan, Bettina Messmer, Martin Jaggi arXiv Mixture-of-Experts Architecture Design Expert Specialization
COLM 2024	Personalized Collaborative Fine-Tuning for On-Device Large Language Models Nicolas Wagner, Dongyang Fan, Martin Jaggi codes / arXiv Collaborative Learning Personalization On-Device Fine-Tuning
AAAI 2024	Ghost Noise for Regularizing Deep Neural Networks Atli Kosson, Dongyang Fan, Martin Jaggi arXiv Regularization Deep Learning Generalization
NeurIPS 2023	Collaborative Learning via Prediction Consensus Dongyang Fan, Celestine Mendler-Dünner, Martin Jaggi codes / arXiv / poster Collaborative Learning Consensus Knowledge Distillation

Academic Service

Reviewer for NeurIPS 2025 (Top Reviewer ⭐️), 2024; ICLR 2025, 2023; COLM 2025 and multiple workshops.
Supervison of student projects: My supervised student projects have resulted in a COLM paper and an oral presentation at a COLM workshop.

Miscellaneous

In general I like arts and cultural stuff. I am also an outdoorsy person and I do hiking skiing and sailing.

I paint from my hiking trips. For example...

Source codes of the website are from here.