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Pang Wei Koh

47 accepted papers

2026

Cold-Start Personalization via Training-Free Priors from Structured World Models

ICML 2026poster

Cold-start personalization requires inferring preferences from minimal interaction when no user-specific historical data is available. The space of possible preferences is vast, yet users care about only a sparse subset and rarely articulate them upfront; combined with limited interaction budgets, t…

Cited by 0SourceScholar
2026

Frustratingly Simple Retrieval Improves Challenging, Reasoning-Intensive Benchmarks

ICLR 2026poster

Retrieval augmentation has primarily been studied in limited settings, such as factoid question answering; more challenging, reasoning-intensive benchmarks have seen limited success from minimal RAG. In this work, we challenge this prevailing view on a set of established, reasoning-intensive benchma…

Cited by 0SourceScholar
2026

Personalized Reasoning: Just-in-time Personalization and Why LLMs Fail at It

ICLR 2026poster

Current large language model (LLM) development treats task-solving and preference-alignment as separate challenges, optimizing first for objective correctness, then for alignment to aggregated human preferences. This paradigm fails in human-facing applications where solving a problem correctly is in…

Cited by 0SourcecodeScholar
2026

Privasis: Synthesizing the Largest "Public" Private Dataset from Scratch

ICML 2026poster

Research involving privacy-sensitive data has always been constrained by data scarcity, standing in sharp contrast to other areas that have benefited from data scaling. To quench this thirst, we present Privasis (i.e., privacy oasis), the first million-scale fully synthetic dataset entirely built fr…

Cited by 0SourceScholar
2026

Proximal Decoding: Provably Reducing Copyright Risk for Any Language Model

ICML 2026poster

Modern language models (LMs) tend to memorize portions of their training data and reproduce verbatim spans. When the underlying sources are sensitive or copyright-protected, such reproduction raises issues of consent and compensation for creators and compliance risks for developers. We propose Proxi…

Cited by 0SourceScholar
2026

RLVE: Scaling Up Reinforcement Learning for Language Models with Adaptive Verifiable Environments

ICML 2026poster

We introduce Reinforcement Learning (RL) with Adaptive Verifiable Environments (RLVE), an approach using verifiable environments that procedurally generate problems and provide algorithmically verifiable rewards, to scale up RL for language models (LMs). RLVE enables each verifiable environment to d…

Cited by 0SourceScholar
2026

Reinforcement Learning with Evolving Rubrics for Deep Research

ICML 2026oral

Deep research agents perform multi-step research to produce long-form, well-attributed answers. However, most open deep research agents are trained on easily verifiable short-form QA tasks via reinforcement learning with verifiable rewards, which does not extend to realistic long-form tasks. We addr…

Cited by 0SourceScholar
2026

Spurious Rewards: Rethinking Training Signals in RLVR

ICML 2026poster

We show that reinforcement learning with verifiable rewards (RLVR) can elicit strong mathematical reasoning in certain language models even with spurious rewards that have little, no, or outright negative correlation with the correct answer. For example, RLVR training with GRPO improves MATH-500 per…

Cited by 0SourcecodeScholar
2025

DataDecide: How to Predict Best Pretraining Data with Small Experiments

ICML 2025poster

Because large language models are expensive to pretrain on different datasets, using smaller-scale experiments to decide on data is crucial for reducing costs. Which benchmarks and methods of making decisions from observed performance at small scale most accurately predict the datasets that yield th…

Cited by 0SourcePDFScholar
2025

Exploring How Generative MLLMs Perceive More Than CLIP with the Same Vision Encoder

ACL 2025long

Recent research has shown that CLIP models struggle with visual reasoning tasks that require grounding compositionality, understanding spatial relationships, or capturing fine-grained details. One natural hypothesis is that the CLIP vision encoder does not embed essential information for these tasks…

2025

FlexOLMo: Open Language Models for Flexible Data Use

NeurIPS 2025spotlight

We introduce FlexOLMo, a new class of language models (LMs) that supports (1) distributed training without data sharing, where different model parameters are independently trained on private datasets, and (2) data-flexible inference, where these parameters along with their associated data can be eas…

Cited by 0SourceScholar
2025

Group-robust Sample Reweighting for Subpopulation Shifts via Influence Functions

ICLR 2025poster

Machine learning models often have uneven performance among subpopulations (a.k.a., groups) in the data distributions. This poses a significant challenge for the models to generalize when the proportions of the groups shift during deployment. To improve robustness to such shifts, existing approaches…

2025

Language models scale reliably with over-training and on downstream tasks

ICLR 2025poster

Scaling laws are useful guides for derisking expensive training runs, as they predict performance of large models using cheaper, small-scale experiments. However, there remain gaps between current scaling studies and how language models are ultimately trained and evaluated. For instance, scaling is…

2025

NICE Data Selection for Instruction Tuning in LLMs with Non-differentiable Evaluation Metric

ICML 2025poster

Curating data for instruction tuning is crucial for enhancing the performance of large language models (LLMs). This work aims to select training data for instruction tuning to improve the LLM performance on specific tasks. Existing methods often rely on next-token prediction (NTP) loss as a proxy fo…

2025

OLMoE: Open Mixture-of-Experts Language Models

ICLR 2025oral

We introduce OLMoE, a fully open, state-of-the-art language model leveraging sparse Mixture-of-Experts (MoE). OLMoE-1B-7B has 7 billion (B) parameters but uses only 1B per input token. We pretrain it on 5 trillion tokens and further adapt it to create OLMoE-1B-7B-Instruct. Our models outperform all…

2025

PLeaS - Merging Models with Permutations and Least Squares

CVPR 2025poster

The democratization of machine learning systems has made the process of fine-tuning accessible to practitioners, leading to a wide range of open-source models fine-tuned on specialized tasks and datasets. Recent work has proposed to merge such models to combine their functionalities. However, prior…

Cited by 5SourcePDFScholar
2025

Precise Information Control in Long-Form Text Generation

NeurIPS 2025poster

A central challenge in language models (LMs) is faithfulness hallucination: the generation of information unsubstantiated by input context. To study this problem, we propose Precise Information Control (PIC), a new task formulation that requires models to generate long-form outputs grounded in a pro…

Cited by 0SourceScholar
2025

S4S: Solving for a Fast Diffusion Model Solver

ICML 2025poster

Diffusion models (DMs) create samples from a data distribution by starting from random noise and iteratively solving a reverse-time ordinary differential equation (ODE). Because each step in the iterative solution requires an expensive neural function evaluation (NFE), there has been significant int…

Cited by 0SourcePDFScholar
2024

Annotation alignment: Comparing LLM and human annotations of conversational safety

EMNLP 2024main

Do LLMs align with human perceptions of safety? We study this question via *annotation alignment*, the extent to which LLMs and humans agree when annotating the safety of user-chatbot conversations. We leverage the recent DICES dataset (Aroyo et al. 2023), in which 350 conversations are each rated f…

Cited by 4SourcePDFScholar
2024

CopyBench: Measuring Literal and Non-Literal Reproduction of Copyright-Protected Text in Language Model Generation

EMNLP 2024main

Evaluating the degree of reproduction of copyright-protected content by language models (LMs) is of significant interest to the AI and legal communities. Although both literal and non-literal similarities are considered by courts when assessing the degree of reproduction, prior research has focused…

2024

DataComp-LM: In search of the next generation of training sets for language models

NeurIPS 2024poster

We introduce DataComp for Language Models, a testbed for controlled dataset experiments with the goal of improving language models. As part of DCLM, we provide a standardized corpus of 240T tokens extracted from Common Crawl, effective pretraining recipes based on the OpenLM framework, and a broad s…

Cited by 64SourcePDFScholar
2024

Improving Domain Generalization with Domain Relations

ICLR 2024spotlight

Distribution shift presents a significant challenge in machine learning, where models often underperform during the test stage when faced with a different distribution than the one they were trained on. In this paper, we focus on domain shifts, which occur when the model is applied to new domains th…

Cited by 11SourcePDFScholar
2024

Instructional Fingerprinting of Large Language Models

NAACL 2024long

The exorbitant cost of training Large language models (LLMs) from scratch makes it essential to fingerprint the models to protect intellectual property via ownership authentication and to ensure downstream users and developers comply with their license terms (eg restricting commercial use). In this…

2024

MediQ: Question-Asking LLMs and a Benchmark for Reliable Interactive Clinical Reasoning

NeurIPS 2024poster

Users typically engage with LLMs interactively, yet most existing benchmarks evaluate them in a static, single-turn format, posing reliability concerns in interactive scenarios. We identify a key obstacle towards reliability: LLMs are trained to answer any question, even with incomplete context or i…

Cited by 16SourcePDFScholar
2024

Merge to Learn: Efficiently Adding Skills to Language Models with Model Merging

EMNLP 2024finding

Adapting general-purpose language models to new skills is currently an expensive process that must be repeated as new instruction datasets targeting new skills are created, or can cause the models to forget older skills. In this work, we investigate the effectiveness of adding new skills to preexist…

2024

Multilingual Diversity Improves Vision-Language Representations

NeurIPS 2024spotlight

Massive web-crawled image-text datasets lay the foundation for recent progress in multimodal learning. These datasets are designed with the goal of training a model to do well on standard computer vision benchmarks, many of which, however, have been shown to be English-centric (e.g., ImageNet). Cons…

Cited by 8SourcePDFScholar
2024

Position Paper: Data-Centric AI in the Age of Large Language Models

EMNLP 2024finding

This position paper proposes a data-centric viewpoint of AI research, focusing on large language models (LLMs). We start by making a key observation that data is instrumental in the developmental (e.g., pretraining and fine-tuning) and inferential stages (e.g., in-context learning) of LLMs, and advo…

Cited by 1SourcePDFScholar
2024

Scaling Retrieval-Based Language Models with a Trillion-Token Datastore

NeurIPS 2024poster

Scaling laws with respect to the amount of training data and the number of parameters allow us to predict the cost-benefit trade-offs of pretraining language models (LMs) in different configurations. In this paper, we consider another dimension of scaling: the amount of data available at inference t…

2024

The Generative AI Paradox: “What It Can Create, It May Not Understand”

ICLR 2024poster

The recent wave of generative AI has sparked unprecedented global attention, with both excitement and concern over potentially superhuman levels of artificial intelligence: models now take only seconds to produce outputs that would challenge or exceed the capabilities even of expert humans. At the s…

Cited by 30SourcePDFScholar
2024

The Unmet Promise of Synthetic Training Images: Using Retrieved Real Images Performs Better

NeurIPS 2024poster

Generative text-to-image models enable us to synthesize unlimited amounts of images in a controllable manner, spurring many recent efforts to train vision models with synthetic data. However, every synthetic image ultimately originates from the upstream data used to train the generator. Does the int…

2024

Uncertainty of Thoughts: Uncertainty-Aware Planning Enhances Information Seeking in LLMs

NeurIPS 2024poster

In the face of uncertainty, the ability to *seek information* is of fundamental importance. In many practical applications, such as medical diagnosis and troubleshooting, the information needed to solve the task is not initially given, and has to be actively sought by asking follow-up questions (for…

Cited by 4SourcePDFScholar
2023

Are aligned neural networks adversarially aligned?

NeurIPS 2023poster

Large language models are now tuned to align with the goals of their creators, namely to be "helpful and harmless." These models should respond helpfully to user questions, but refuse to answer requests that could cause harm. However, adversarial users can construct inputs which circumvent attempts…

Cited by 312SourcePDFScholar
2023

DataComp: In search of the next generation of multimodal datasets

NeurIPS 2023oral

Multimodal datasets are a critical component in recent breakthroughs such as CLIP, Stable Diffusion and GPT-4, yet their design does not receive the same research attention as model architectures or training algorithms. To address this shortcoming in the machine learning ecosystem, we introduce Data…

2023

FActScore: Fine-grained Atomic Evaluation of Factual Precision in Long Form Text Generation

EMNLP 2023long main

Evaluating the factuality of long-form text generated by large language models (LMs) is non-trivial because (1) generations often contain a mixture of supported and unsupported pieces of information, making binary judgments of quality inadequate, and (2) human evaluation is time-consuming and costly…

Cited by 0SourcecodeScholar
2023

On the Trade-off of Intra-/Inter-class Diversity for Supervised Pre-training

NeurIPS 2023poster

Pre-training datasets are critical for building state-of-the-art machine learning models, motivating rigorous study on their impact on downstream tasks. In this work, we study the impact of the trade-off between the intra-class diversity (the number of samples per class) and the inter-class diversit…

Cited by 11SourcePDFScholar
2023

Out-of-Domain Robustness via Targeted Augmentations

ICML 2023poster

Models trained on one set of domains often suffer performance drops on unseen domains, e.g., when wildlife monitoring models are deployed in new camera locations. In this work, we study principles for designing data augmentations for out-of-domain (OOD) generalization. In particular, we focus on rea…

2023

Proximity-Informed Calibration for Deep Neural Networks

NeurIPS 2023spotlight

Confidence calibration is central to providing accurate and interpretable uncertainty estimates, especially under safety-critical scenarios. However, we find that existing calibration algorithms often overlook the issue of proximity bias, a phenomenon where models tend to be more overconfident in lo…

2022

Extending the WILDS Benchmark for Unsupervised Adaptation

ICLR 2022oral

Machine learning systems deployed in the wild are often trained on a source distribution but deployed on a different target distribution. Unlabeled data can be a powerful point of leverage for mitigating these distribution shifts, as it is frequently much more available than labeled data and can oft…

Cited by 143SourcePDFScholar
2022

Wild-Time: A Benchmark of in-the-Wild Distribution Shift over Time

NeurIPS 2022accept

Distribution shifts occur when the test distribution differs from the training distribution, and can considerably degrade performance of machine learning models deployed in the real world. While recent works have studied robustness to distribution shifts, distribution shifts arising from the passage…

2021

Accuracy on the Line: on the Strong Correlation Between Out-of-Distribution and In-Distribution Generalization

ICML 2021spotlight

For machine learning systems to be reliable, we must understand their performance in unseen, out- of-distribution environments. In this paper, we empirically show that out-of-distribution performance is strongly correlated with in-distribution performance for a wide range of models and distribution…

Cited by 333SourcePDFScholar
2021

Just Train Twice: Improving Group Robustness without Training Group Information

ICML 2021oral

Standard training via empirical risk minimization (ERM) can produce models that achieve low error on average but high error on minority groups, especially in the presence of spurious correlations between the input and label. Prior approaches to this problem, like group distributionally robust optimi…

2021

Selective Classification Can Magnify Disparities Across Groups

ICLR 2021poster

Selective classification, in which models can abstain on uncertain predictions, is a natural approach to improving accuracy in settings where errors are costly but abstentions are manageable. In this paper, we find that while selective classification can improve average accuracies, it can simultaneo…

Cited by 62SourcePDFScholar
2021

WILDS: A Benchmark of in-the-Wild Distribution Shifts

ICML 2021oral

Distribution shifts—where the training distribution differs from the test distribution—can substantially degrade the accuracy of machine learning (ML) systems deployed in the wild. Despite their ubiquity in the real-world deployments, these distribution shifts are under-represented in the datasets w…

2020

An Investigation of Why Overparameterization Exacerbates Spurious Correlations

ICML 2020poster

We study why overparameterization—increasing model size well beyond the point of zero training error—can hurt test error on minority groups despite improving average test error when there are spurious correlations in the data. Through simulations and experiments on two image datasets, we identify tw…

2020

Concept Bottleneck Models

ICML 2020poster

We seek to learn models that we can interact with using high-level concepts: if the model did not think there was a bone spur in the x-ray, would it still predict severe arthritis? State-of-the-art models today do not typically support the manipulation of concepts like "the existence of bone spurs",…

2019

Inferring Multidimensional Rates of Aging from Cross-Sectional Data

AISTATS 2019poster

Modeling how individuals evolve over time is a fundamental problem in the natural and social sciences. However, existing datasets are often cross-sectional with each individual observed only once, making it impossible to apply traditional time-series methods. Motivated by the study of human aging, w…