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Linjun Zhang

36 accepted papers

2026

Alternating Reinforcement Learning for Rubric-Based Reward Modeling in Non-Verifiable LLM Post-Training

ICML 2026poster

Standard reward models typically predict scalar scores that fail to capture the multifaceted nature of response quality in non-verifiable domains, such as creative writing or open-ended instruction following. To address this limitation, we propose Rubric-ARM, a framework that jointly optimizes a rub…

Cited by 0SourceScholar
2026

Evaluating LLMs When They Do Not Know the Answer: Statistical Evaluation of Mathematical Reasoning via Comparative Signals

ICML 2026poster

Evaluating mathematical reasoning in LLMs is constrained by limited benchmark sizes and inherent model stochasticity, yielding high-variance accuracy estimates and unstable rankings across platforms. On difficult problems, an LLM may fail to produce a correct final answer, yet still provide reliable…

Cited by 0SourceScholar
2026

MMedAgent-RL: Optimizing Multi-Agent Collaboration for Multimodal Medical Reasoning

ICLR 2026poster

Medical Large Vision-Language Models (Med-LVLMs) have shown strong potential in multimodal diagnostic tasks. However, existing single-agent models struggle to generalize across diverse medical specialties, limiting their performance. Recent efforts introduce multi-agent collaboration frameworks insp…

Cited by 0SourceScholar
2026

Optimas: Optimizing Compound AI Systems with Globally Aligned Local Rewards

ICLR 2026poster

Compound AI systems integrating multiple components, such as Large Language Models, specialized tools, and traditional machine learning models, are increasingly deployed to solve complex real-world tasks. However, optimizing compound systems remains challenging due to their non-differentiable struct…

Cited by 0SourceScholar
2026

Residual Feature Integration is Sufficient to Prevent Negative Transfer

ICLR 2026poster

Transfer learning has become a central paradigm in modern machine learning, yet it suffers from the long-standing problem of negative transfer, where leveraging source representations can harm rather than help performance on the target task. Although empirical remedies have been proposed, there rema…

Cited by 0SourcecodeScholar
2026

Secret-Protected Evolution for Differentially Private Synthetic Text Generation

ICLR 2026poster

Text data has become extremely valuable on large language models (LLMs) and even lead to general artificial intelligence (AGI). A lot of high-quality text in the real world is private and cannot be freely used due to privacy concerns. Therefore, differentially private (DP) synthetic text generation…

Cited by 0SourceScholar
2025

AceSearcher: Bootstrapping Reasoning and Search for LLMs via Reinforced Self-Play

NeurIPS 2025spotlight

Search-augmented LLMs often struggle with complex reasoning tasks due to ineffective multi-hop retrieval and limited reasoning ability. We propose AceSearcher, a cooperative self-play framework that trains a single large language model (LLM) to alternate between two roles: a decomposer that breaks d…

Cited by 0SourceScholar
2025

FactTest: Factuality Testing in Large Language Models with Finite-Sample and Distribution-Free Guarantees

ICML 2025poster

The propensity of large language models (LLMs) to generate hallucinations and non-factual content undermines their reliability in high-stakes domains, where rigorous control over Type I errors (the conditional probability of incorrectly classifying hallucinations as truthful content) is essential. D…

Cited by 0SourcePDFScholar
2025

MMed-RAG: Versatile Multimodal RAG System for Medical Vision Language Models

ICLR 2025poster

Artificial Intelligence (AI) has demonstrated significant potential in healthcare, particularly in disease diagnosis and treatment planning. Recent progress in Medical Large Vision-Language Models (Med-LVLMs) has opened up new possibilities for interactive diagnostic tools. However, these models oft…

2025

MPO: An Efficient Post-Processing Framework for Mixing Diverse Preference Alignment

ICML 2025poster

Reinforcement Learning from Human Feedback (RLHF) has shown promise in aligning large language models (LLMs). Yet its reliance on a singular reward model often overlooks the diversity of human preferences. Recent approaches address this limitation by leveraging multi-dimensional feedback to fine-tun…

Cited by 0SourcePDFScholar
2025

Mitigating Heterogeneous Token Overfitting in LLM Knowledge Editing

ICML 2025poster

Large language models (LLMs) have achieved remarkable performance on various natural language tasks. However, they are trained on static corpora and their knowledge can become outdated quickly in the fast-changing world. This motivates the development of knowledge editing (KE) to update specific kn…

Cited by 3SourcePDFScholar
2025

RoseRAG: Robust Retrieval-augmented Generation with Small-scale LLMs via Margin-aware Preference Optimization

ACL 2025finding

Large language models (LLMs) have achieved impressive performance but face high computational costs and latency, limiting their deployment in resource-constrained settings. In contrast, small-scale LLMs (SLMs) are more efficient yet struggle to capture evolving real-world knowledge. Retrieval-augmen…

2024

Analyzing and Mitigating Object Hallucination in Large Vision-Language Models

ICLR 2024poster

Large vision-language models (LVLMs) have shown remarkable abilities in understanding visual information with human languages. However, LVLMs still suffer from object hallucination, which is the problem of generating descriptions that include objects that do not actually exist in the images. This ca…

2024

Calibrated Self-Rewarding Vision Language Models

NeurIPS 2024poster

Large Vision-Language Models (LVLMs) have made substantial progress by integrating pre-trained large language models (LLMs) and vision models through instruction tuning. Despite these advancements, LVLMs often exhibit the hallucination phenomenon, where generated text responses appear linguistically…

2024

Conformal Prediction for Deep Classifier via Label Ranking

ICML 2024poster

Conformal prediction is a statistical framework that generates prediction sets containing ground-truth labels with a desired coverage guarantee. The predicted probabilities produced by machine learning models are generally miscalibrated, leading to large prediction sets in conformal prediction. To a…

2024

Fair Risk Control: A Generalized Framework for Calibrating Multi-group Fairness Risks

ICML 2024poster

This paper introduces a framework for post-processing machine learning models so that their predictions satisfy multi-group fairness guarantees. Based on the celebrated notion of multicalibration, we introduce $(s,g,\alpha)-$GMC (Generalized Multi-Dimensional Multicalibration) for multi-dimensional…

Cited by 4SourcePDFScholar
2024

Order-Independence Without Fine Tuning

NeurIPS 2024poster

The development of generative language models that can create long and coherent textual outputs via autoregression has lead to a proliferation of uses and a corresponding sweep of analyses as researches work to determine the limitations of this new paradigm. Unlike humans, these '*Large Language Mod…

2024

RULE: Reliable Multimodal RAG for Factuality in Medical Vision Language Models

EMNLP 2024main

The recent emergence of Medical Large Vision Language Models (Med-LVLMs) has enhanced medical diagnosis. However, current Med-LVLMs frequently encounter factual issues, often generating responses that do not align with established medical facts. Retrieval-Augmented Generation (RAG), which utilizes e…

2024

S$^{2}$FT: Efficient, Scalable and Generalizable LLM Fine-tuning by Structured Sparsity

NeurIPS 2024poster

Current PEFT methods for LLMs can achieve high quality, efficient training, or scalable serving, but not all three simultaneously. To address this limitation, we investigate sparse fine-tuning and observe a remarkable improvement in generalization ability. Utilizing this key insight, we propose a…

Cited by 3SourcePDFScholar
2023

Beyond Confidence: Reliable Models Should Also Consider Atypicality

NeurIPS 2023poster

While most machine learning models can provide confidence in their predictions, confidence is insufficient to understand a prediction's reliability. For instance, the model may have a low confidence prediction if the input is not well-represented in the training dataset or if the input is inherently…

2023

Discover and Cure: Concept-aware Mitigation of Spurious Correlation

ICML 2023poster

Deep neural networks often rely on spurious correlations to make predictions, which hinders generalization beyond training environments. For instance, models that associate cats with bed backgrounds can fail to predict the existence of cats in other environments without beds. Mitigating spurious cor…

2023

FIFA: Making Fairness More Generalizable in Classifiers Trained on Imbalanced Data

ICLR 2023poster

Algorithmic fairness plays an important role in machine learning and imposing fairness constraints during learning is a common approach. However, many datasets are imbalanced in certain label classes (e.g. "healthy") and sensitive subgroups (e.g. "older patients"). Empirically, this imbalance leads…

Cited by 19SourcePDFScholar
2023

FaiREE: fair classification with finite-sample and distribution-free guarantee

ICLR 2023poster

Algorithmic fairness plays an increasingly critical role in machine learning research. Several group fairness notions and algorithms have been proposed. However, the fairness guarantee of existing fair classification methods mainly depend on specific data distributional assumptions, often requiring…

2023

Freeze then Train: Towards Provable Representation Learning under Spurious Correlations and Feature Noise

AISTATS 2023poster

The existence of spurious correlations such as image backgrounds in the training environment can make empirical risk minimization (ERM) perform badly in the test environment. To address this problem, Kirichenko et al. (2022) empirically found that the core features that are related to the outcome ca…

2023

Reinforcement Learning with Stepwise Fairness Constraints

AISTATS 2023poster

AI methods are used in societally important settings, ranging from credit to employment to housing, and it is crucial to provide fairness in regard to automated decision making. Moreover, many settings are dynamic, with populations responding to sequential decision policies. We introduce the study o…

Cited by 15SourcePDFScholar
2023

Understanding Multimodal Contrastive Learning and Incorporating Unpaired Data

AISTATS 2023poster

Language-supervised vision models have recently attracted great attention in computer vision. A common approach to build such models is to use contrastive learning on paired data across the two modalities, as exemplified by Contrastive Language-Image Pre-Training (CLIP). In this paper, (i) we initia…

2022

C-Mixup: Improving Generalization in Regression

NeurIPS 2022accept

Improving the generalization of deep networks is an important open challenge, particularly in domains without plentiful data. The mixup algorithm improves generalization by linearly interpolating a pair of examples and their corresponding labels. These interpolated examples augment the original trai…

2022

Improving Out-of-Distribution Robustness via Selective Augmentation

ICML 2022spotlight

Machine learning algorithms typically assume that training and test examples are drawn from the same distribution. However, distribution shift is a common problem in real-world applications and can cause models to perform dramatically worse at test time. In this paper, we specifically consider the p…

2021

A Central Limit Theorem for Differentially Private Query Answering

NeurIPS 2021spotlight

Perhaps the single most important use case for differential privacy is to privately answer numerical queries, which is usually achieved by adding noise to the answer vector. The central question is, therefore, to understand which noise distribution optimizes the privacy-accuracy trade-off, especiall…

Cited by 12SourcePDFScholar
2021

Adversarial Training Helps Transfer Learning via Better Representations

NeurIPS 2021poster

Transfer learning aims to leverage models pre-trained on source data to efficiently adapt to target setting, where only limited data are available for model fine-tuning. Recent works empirically demonstrate that adversarial training in the source data can improve the ability of models to transfer to…

Cited by 63SourcePDFScholar
2021

How Does Mixup Help With Robustness and Generalization?

ICLR 2021spotlight

Mixup is a popular data augmentation technique based on on convex combinations of pairs of examples and their labels. This simple technique has shown to substantially improve both the model's robustness as well as the generalization of the trained model. However, it is not well-understood why such…

Cited by 313SourcePDFScholar
2021

Improving Adversarial Robustness via Unlabeled Out-of-Domain Data

AISTATS 2021poster

Data augmentation by incorporating cheap unlabeled data from multiple domains is a powerful way to improve prediction especially when there is limited labeled data. In this work, we investigate how adversarial robustness can be enhanced by leveraging out-of-domain unlabeled data. We demonstrate that…

Cited by 28SourcePDFScholar
2021

Improving Generalization in Meta-learning via Task Augmentation

ICML 2021spotlight

Meta-learning has proven to be a powerful paradigm for transferring the knowledge from previous tasks to facilitate the learning of a novel task. Current dominant algorithms train a well-generalized model initialization which is adapted to each task via the support set. The crux lies in optimizing t…

2020

Interpreting Robust Optimization via Adversarial Influence Functions

ICML 2020poster

Robust optimization has been widely used in nowadays data science, especially in adversarial training. However, little research has been done to quantify how robust optimization changes the optimizers and the prediction losses comparing to standard training. In this paper, inspired by the influence…

Cited by 16SourcePDFScholar