Hanlin Zhang
@hlzhang109.bsky.social
CS PhD candidate @Harvard https://hanlin-zhang.com
Announcing our COLM 2026 workshop: Scientific Understanding of Foundation Models: we invite submissions on training dynamics, scaling laws, data and optimization, post-training, reward modeling, evaluation science, reliability, reproducibility, and theoretical understanding of foundation models.
Learning from feedback is instrumental but human preference data can be expensive. How much reward supervision could we get from raw web text instead, without human labels? Our work, a year of incredible effort by @fjxdaisy.bsky.social, advances pure RLHF training across multiple models and tasks.
Introducing EvoLM, a model suite with 100+ decoder-only LMs (1B/4B) trained from scratch, across four training stages — 🟦 Pre-training 🟩 Continued Pre-Training (CPT) 🟨 Supervised Fine-Tuning (SFT) 🟥 Reinforcement Learning (RL)
EvoLM: In Search of Lost Language Model Training Dynamics
Modern language model (LM) training has been divided into multiple stages, making it difficult for downstream developers to evaluate the impact of design choices made at each stage. We present EvoLM, ...
arxiv.org
New work [JSKZ25] w/ Jikai, Vasilis, @shamkakade.bsky.social . We introduce new formulations and tools for evaluating LM capabilities, which help explain observations of post-training behaviors of Qwen-series models. More details: - hanlin-zhang.com/causal-capab... - x.com/_hanlin_zhan...
I want to reshare @brandfonbrener.bsky.social's @NeurIPSConf 2024 paper on CoLoR-Filter: A simple yet powerful method for selecting high-quality data for language model pre-training! With @hlzhang109.bsky.social @schwarzjn.bsky.social @shamkakade.bsky.social
(1/n) 💡How can we speed up the serial runtime of long pre-training runs? Enter Critical Batch Size (CBS): the tipping point where the gains of data parallelism balance with diminishing efficiency. Doubling batch size halves the optimization steps—until we hit CBS, beyond which returns diminish.
LLM self-improvement has critical implications in synthetic data, post-training and test-time inference. To understand LLMs' true capability of self-improvement, we perform large-scale experiments with multiple families of LLMs, tasks and mechanisms. Here is what we found: (1/9)