activity
20242026
collaborators

11 papers

cs.LG2026

Fantastic Pretraining Optimizers and Where to Find Them II: Hyperball Optimization

Kaiyue Wen, Xingyu Dang, Kaifeng Lyu +2

Matrix based optimizers such as Muon can substantially speed up language model pretraining, but their gains over AdamW are observed to shrink as model size and data scale grow when…

cs.LG2026

Data Mixing Can Induce Phase Transitions in Knowledge Acquisition

Xinran Gu, Kaifeng Lyu, Jiazheng Li +1

Large Language Models (LLMs) are typically trained on data mixtures: most data come from web scrapes, while a small portion is curated from high-quality sources with dense domain-s…

cs.LG2026

Can Small Training Runs Reliably Guide Data Curation? Rethinking Proxy-Model Practice

Jiachen T. Wang, Tong Wu, Kaifeng Lyu +4

Data teams at frontier AI companies routinely train small proxy models to make critical decisions about pretraining data recipes for full-scale training runs. However, the communit…

cs.LG2025

Weak-to-Strong Generalization Even in Random Feature Networks, Provably

Marko Medvedev, Kaifeng Lyu, Dingli Yu +3

Weak-to-Strong Generalization (Burns et al., 2024) is the phenomenon whereby a strong student, say GPT-4, learns a task from a weak teacher, say GPT-2, and ends up significantly ou…

cs.LG2025

Shift is Good: Mismatched Data Mixing Improves Test Performance

Marko Medvedev, Kaifeng Lyu, Zhiyuan Li +1

We consider training and testing on mixture distributions with different training and test proportions. We show that in many settings, and in some sense generically, distribution s…

cs.LG2025

Towards Understanding Text Hallucination of Diffusion Models via Local Generation Bias

Rui Lu, Runzhe Wang, Kaifeng Lyu +3

Score-based diffusion models have achieved incredible performance in generating realistic images, audio, and video data. While these models produce high-quality samples with impres…