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Kaifeng Lyu

31 accepted papers

2026

Beyond Problem Solving: UOJ-Bench for Evaluating Code Generation, Hacking, and Repair in Competitive Programming

ICML 2026poster

Despite strong performance in competitive programming, the role of Large Language Models (LLMs) in supporting human learning in the same setting remains largely unexplored. In this work, we introduce **UOJ-Bench**, a benchmark designed to evaluate not only the problem-solving ability of LLMs, but al…

Cited by 0SourceScholar
2026

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

ICLR 2026poster

Data teams at frontier AI companies routinely train small proxy models to make critical decisions about pretraining data recipes for full-scale training. However, the community has a limited understanding of whether and when conclusions drawn from small-scale experiments reliably transfer to large-s…

Cited by 0SourcecodeScholar
2026

How Learning Rate Decay Wastes Your Best Data in Curriculum-Based LLM Pretraining

ICLR 2026oral

Due to the scarcity of high-quality data, large language models (LLMs) are often trained on mixtures of data with varying quality levels, even after sophisticated data curation. A natural approach to better leverage high-quality data is curriculum-based pretraining, where the model is trained on dat…

Cited by 0SourceScholar
2026

Larger Datasets Can Be Repeated More: A Theoretical Analysis of Multi-Epoch Scaling in Linear Regression

ICLR 2026poster

Large Language Model (LLM) training often processes vast text corpora in a single pass, leaving much available data underutilized. This paper presents a theoretical analysis of how a common workaround, training for multiple epochs on the same dataset, reshapes the data scaling laws. Concretely, give…

Cited by 0SourceScholar
2025

A Multi-Power Law for Loss Curve Prediction Across Learning Rate Schedules

ICLR 2025poster

Training large models is both resource-intensive and time-consuming, making it crucial to understand the quantitative relationship between model performance and hyperparameters. In this paper, we derive an empirical law that predicts pretraining loss for large language models for every intermediate…

2025

Adam Reduces a Unique Form of Sharpness: Theoretical Insights Near the Minimizer Manifold

NeurIPS 2025poster

Despite the popularity of Adam optimizer in practice, most theoretical analyses study SGD as a proxy and little is known about how the solutions found by Adam differ. In this paper, we show that Adam reduces a specific form of sharpness measure shaped by its adaptive updates, leading to qualitativel…

Cited by 0SourceScholar
2025

Data Mixing Can Induce Phase Transitions in Knowledge Acquisition

NeurIPS 2025spotlight

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-specific knowledge. In this paper, we show that when training LLMs on such data mixtures, knowledge acquisition from know…

Cited by 0SourceScholar
2025

Efficient stagewise pretraining via progressive subnetworks

ICLR 2025poster

Recent developments in large language models have sparked interest in efficient pretraining methods. Stagewise training approaches to improve efficiency, like gradual stacking and layer dropping (Reddi et al., 2023; Zhang & He, 2020), have recently garnered attention. The prevailing view suggests th…

Cited by 8SourcePDFScholar
2025

Feature Averaging: An Implicit Bias of Gradient Descent Leading to Non-Robustness in Neural Networks

ICLR 2025poster

In this work, we investigate a particular implicit bias in gradient descent training, which we term “Feature Averaging,” and argue that it is one of the principal factors contributing to the non-robustness of deep neural networks. We show that, even when multiple discriminative features are present…

Cited by 1SourcePDFScholar
2025

How Far Are We from Optimal Reasoning Efficiency?

NeurIPS 2025poster

Large Reasoning Models (LRMs) demonstrate remarkable problem-solving capabilities through extended Chain-of-Thought (CoT) reasoning but often produce excessively verbose and redundant reasoning traces. This inefficiency incurs high inference costs and limits practical deployment. While existing fine…

Cited by 0SourcecodeScholar
2025

RNNs are not Transformers (Yet): The Key Bottleneck on In-Context Retrieval

ICLR 2025poster

This paper investigates the gap in representation powers of Transformers and Recurrent Neural Networks (RNNs), which are more memory efficient than Transformers. We aim to understand whether RNNs can match the performance of Transformers, particularly when enhanced with Chain-of-Thought (CoT) prompt…

2025

Safety Alignment Should be Made More Than Just a Few Tokens Deep

ICLR 2025oral

The safety alignment of current Large Language Models (LLMs) is vulnerable. Simple attacks, or even benign fine-tuning, can jailbreak aligned models. We note that many of these vulnerabilities are related to a shared underlying issue: safety alignment can take shortcuts, wherein the alignment adapts…

2025

Towards Understanding Text Hallucination of Diffusion Models via Local Generation Bias

ICLR 2025poster

Score-based diffusion models have achieved incredible performance in generating realistic images, audio, and video data. While these models produce high-quality samples with impressive details, they often introduce unrealistic artifacts, such as distorted fingers or hallucinated texts with no meanin…

Cited by 0SourcePDFScholar
2025

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

ICML 2025poster

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 outperforming the teacher. We show that this phenomenon does not require a complex and pretrained learner like GPT-4, can a…

Cited by 0SourcePDFScholar
2024

A Quadratic Synchronization Rule for Distributed Deep Learning

ICLR 2024poster

In distributed deep learning with data parallelism, synchronizing gradients at each training step can cause a huge communication overhead, especially when many nodes work together to train large models. Local gradient methods, such as Local SGD, address this issue by allowing workers to compute lo…

2024

Dichotomy of Early and Late Phase Implicit Biases Can Provably Induce Grokking

ICLR 2024poster

Recent work by Power et al. (2022) highlighted a surprising "grokking" phenomenon in learning arithmetic tasks: a neural net first "memorizes" the training set, resulting in perfect training accuracy but near-random test accuracy, and after training for sufficiently longer, it suddenly transitions t…

2024

DistillSpec: Improving Speculative Decoding via Knowledge Distillation

ICLR 2024poster

Speculative decoding~(SD) accelerates large language model inference by employing a faster {\em draft} model for generating multiple tokens, which are then verified in parallel by the larger {\em target} model, resulting in the text generated according to the target model distribution. However, iden…

Cited by 86SourcePDFScholar
2024

Keeping LLMs Aligned After Fine-tuning: The Crucial Role of Prompt Templates

NeurIPS 2024poster

Public LLMs such as the Llama 2-Chat underwent alignment training and were considered safe. Recently Qi et al. (2024) reported that even benign fine-tuning on seemingly safe datasets can give rise to unsafe behaviors in the models. The current paper is about methods and best practices to mitigate su…

2024

The Marginal Value of Momentum for Small Learning Rate SGD

ICLR 2024poster

Momentum is known to accelerate the convergence of gradient descent in strongly convex settings without stochastic gradient noise. In stochastic optimization, such as training neural networks, folklore suggests that momentum may help deep learning optimization by reducing the variance of the stochas…

Cited by 12SourcePDFScholar
2023

Understanding Incremental Learning of Gradient Descent: A Fine-grained Analysis of Matrix Sensing

ICML 2023poster

It is believed that Gradient Descent (GD) induces an implicit bias towards good generalization in training machine learning models. This paper provides a fine-grained analysis of the dynamics of GD for the matrix sensing problem, whose goal is to recover a low-rank ground-truth matrix from near-isot…

Cited by 41SourcePDFScholar
2023

Why (and When) does Local SGD Generalize Better than SGD?

ICLR 2023poster

Local SGD is a communication-efficient variant of SGD for large-scale training, where multiple GPUs perform SGD independently and average the model parameters periodically. It has been recently observed that Local SGD can not only achieve the design goal of reducing the communication overhead but al…

2022

New Definitions and Evaluations for Saliency Methods: Staying Intrinsic, Complete and Sound

NeurIPS 2022accept

Saliency methods compute heat maps that highlight portions of an input that were most important for the label assigned to it by a deep net. Evaluations of saliency methods convert this heat map into a new masked input by retaining the $k$ highest-ranked pixels of the original input and replacing the…

2022

On the SDEs and Scaling Rules for Adaptive Gradient Algorithms

NeurIPS 2022accept

Approximating Stochastic Gradient Descent (SGD) as a Stochastic Differential Equation (SDE) has allowed researchers to enjoy the benefits of studying a continuous optimization trajectory while carefully preserving the stochasticity of SGD. Analogous study of adaptive gradient methods, such as RMSpro…

2022

Understanding the Generalization Benefit of Normalization Layers: Sharpness Reduction

NeurIPS 2022accept

Normalization layers (e.g., Batch Normalization, Layer Normalization) were introduced to help with optimization difficulties in very deep nets, but they clearly also help generalization, even in not-so-deep nets. Motivated by the long-held belief that flatter minima lead to better generalization, th…

Cited by 89SourcePDFScholar
2021

Gradient Descent on Two-layer Nets: Margin Maximization and Simplicity Bias

NeurIPS 2021poster

The generalization mystery of overparametrized deep nets has motivated efforts to understand how gradient descent (GD) converges to low-loss solutions that generalize well. Real-life neural networks are initialized from small random values and trained with cross-entropy loss for classification (unli…

Cited by 101SourcePDFScholar
2021

Towards Resolving the Implicit Bias of Gradient Descent for Matrix Factorization: Greedy Low-Rank Learning

ICLR 2021poster

Matrix factorization is a simple and natural test-bed to investigate the implicit regularization of gradient descent. Gunasekar et al. (2017) conjectured that gradient flow with infinitesimal initialization converges to the solution that minimizes the nuclear norm, but a series of recent papers argu…

Cited by 155SourcePDFScholar
2020

Reconciling Modern Deep Learning with Traditional Optimization Analyses: The Intrinsic Learning Rate

NeurIPS 2020poster

Recent works (e.g., (Li \& Arora, 2020)) suggest that the use of popular normalization schemes (including Batch Normalization) in today's deep learning can move it far from a traditional optimization viewpoint, e.g., use of exponentially increasing learning rates. The current paper highlights other…

Cited by 85SourcePDFScholar