← Search

Hanning Zhang

5 accepted papers

2025

Optimizing Chain-of-Thought Reasoners via Gradient Variance Minimization in Rejection Sampling and RL

NeurIPS 2025poster

Chain-of-thought (CoT) reasoning in large language models (LLMs) can be formalized as a latent variable problem, where the model needs to generate intermediate reasoning steps. While prior approaches such as iterative reward-ranked fine-tuning (RAFT) have relied on such formulations, they typically…

Cited by 0SourcecodeScholar
2025

ScaleBiO: Scalable Bilevel Optimization for LLM Data Reweighting

ACL 2025long

Bilevel optimization has shown its utility across various machine learning settings, yet most algorithms in practice require second-order information, making it challenging to scale them up. Only recently, a paradigm of first-order algorithms has emerged in the theoretical literature, capable of eff…

2025

Understanding Overadaptation in Supervised Fine-Tuning: The Role of Ensemble Methods

ICML 2025poster

Supervised fine-tuning (SFT) on domain-specific data is the dominant approach for adapting foundation models to specialized tasks. However, it has been observed that SFT models tend to forget knowledge acquired during pretraining. In vision models, ensembling a pretrained model with its fine-tuned c…

Cited by 0SourcePDFScholar
2024

Mitigating the Alignment Tax of RLHF

EMNLP 2024main

LLMs acquire a wide range of abilities during pre-training, but aligning LLMs under Reinforcement Learning with Human Feedback (RLHF) can lead to forgetting pretrained abilities, which is also known as the alignment tax. To investigate alignment tax, we conducted experiments with existing RLHF algor…

2024

R-Tuning: Instructing Large Language Models to Say ‘I Don’t Know’

NAACL 2024long

Large language models (LLMs) have revolutionized numerous domains with their impressive performance but still face their challenges. A predominant issue is the propensity for these models to generate non-existent facts, a concern termed hallucination. Our research is motivated by the observation tha…