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Sean Welleck

45 accepted papers

2026

OptimalThinkingBench: Evaluating Over and Underthinking in LLMs

ICLR 2026poster

Thinking LLMs solve complex tasks at the expense of increased compute and overthinking on simpler problems, while non-thinking LLMs are faster and cheaper but underthink on harder reasoning problems. This has led to the development of separate thinking and non-thinking LLM variants, leaving the onus…

Cited by 0SourcecodeScholar
2026

Propose, Solve, Verify: Self-Play Through Formal Verification

ICML 2026poster

Training models through self-play alone (without any human data) has been a longstanding goal in AI, but its effectiveness for training large language models remains unclear, particularly in code generation where rewards based on unit tests are brittle and prone to error propagation. We study self-p…

Cited by 0SourceScholar
2026

RefineBench: Evaluating Refinement Capability in Language Models

ICLR 2026poster

Can language models (LMs) self-refine their own responses? This question is increasingly relevant as more than 10% of real-world user interactions involve refinement requests (see Appendix G). Yet prior studies have largely tested LMs on verifiable tasks such as competition math or symbolic reasonin…

Cited by 0SourceScholar
2026

The CoT Encyclopedia: Analyzing, Predicting, and Controlling how a Reasoning Model will Think

ICLR 2026poster

Long chain-of-thought (CoT) is an essential ingredient in effective usage of modern large language models, but our understanding of the reasoning strategies underlying these capabilities remains limited. While some prior works have attempted to categorize CoTs using predefined strategy types, such a…

Cited by 0SourceScholar
2025

AlphaVerus: Bootstrapping Formally Verified Code Generation through Self-Improving Translation and Treefinement

ICML 2025poster

Automated code generation with large language models has gained significant traction, but there remains no guarantee of the correctness of generated code. We aim to use formal verification to provide mathematical guarantees that the generated code is correct. However, generating formally verified co…

Cited by 7SourcePDFScholar
2025

Evaluating Language Models as Synthetic Data Generators

ACL 2025long

Given the increasing use of synthetic data in language model (LM) post-training, an LM’s ability to generate high-quality data has become nearly as crucial as its ability to solve problems directly. While prior works have focused on developing effective data generation methods, they lack systematic…

2025

ImProver: Agent-Based Automated Proof Optimization

ICLR 2025poster

Large language models (LLMs) have been used to generate formal proofs of mathematical theorems in proofs assistants such as Lean. However, we often want to optimize a formal proof with respect to various criteria, depending on its downstream use. For example, we may want a proof to adhere to a certa…

2025

Inference Scaling Laws: An Empirical Analysis of Compute-Optimal Inference for LLM Problem-Solving

ICLR 2025poster

While the scaling laws of large language models (LLMs) training have been extensively studied, optimal inference configurations of LLMs remain underexplored. We study inference scaling laws (aka test-time scaling laws) and compute-optimal inference, focusing on the trade-offs between model sizes an…

Cited by 10SourcePDFScholar
2025

The BiGGen Bench: A Principled Benchmark for Fine-grained Evaluation of Language Models with Language Models

NAACL 2025long

As language models (LMs) become capable of handling a wide range of tasks, their evaluation is becoming as challenging as their development. Most generation benchmarks currently assess LMs using abstract evaluation criteria-like helpfulness and harmlessness-which often lack the flexibility and granu…

2024

Easy-to-Hard Generalization: Scalable Alignment Beyond Human Supervision

NeurIPS 2024poster

Current AI alignment methodologies rely on human-provided demonstrations or judgments, and the learned capabilities of AI systems would be upper-bounded by human capabilities as a result. This raises a challenging research question: How can we keep improving the systems when their capabilities have…

2024

Llemma: An Open Language Model for Mathematics

ICLR 2024poster

We present Llemma, a large language model for mathematics. We continue pretraining Code Llama on the Proof-Pile-2, a mixture of scientific papers, web data containing mathematics, and mathematical code, yielding Llemma. On the MATH benchmark Llemma outperforms all known openly released models, as we…

Cited by 320SourcePDFScholar
2024

Prometheus 2: An Open Source Language Model Specialized in Evaluating Other Language Models

EMNLP 2024main

Proprietary LMs such as GPT-4 are often employed to assess the quality of responses from various LMs. However, concerns including transparency, controllability, and affordability strongly motivate the development of open-source LMs specialized in evaluations. On the other hand, existing open evaluat…

2023

A Survey of Deep Learning for Mathematical Reasoning

ACL 2023long

Mathematical reasoning is a fundamental aspect of human intelligence and is applicable in various fields, including science, engineering, finance, and everyday life. The development of artificial intelligence (AI) systems capable of solving math problems and proving theorems in language has garnered…

2023

Draft, Sketch, and Prove: Guiding Formal Theorem Provers with Informal Proofs

ICLR 2023top-5%

The formalization of existing mathematical proofs is a notoriously difficult process. Despite decades of research on automation and proof assistants, writing formal proofs remains arduous and only accessible to a few experts. While previous studies to automate formalization focused on powerful searc…

Cited by 172SourcePDFScholar
2023

Faith and Fate: Limits of Transformers on Compositionality

NeurIPS 2023spotlight

Transformer large language models (LLMs) have sparked admiration for their exceptional performance on tasks that demand intricate multi-step reasoning. Yet, these models simultaneously show failures on surprisingly trivial problems. This begs the question: Are these errors incidental, or do they si…

2023

Generating Sequences by Learning to Self-Correct

ICLR 2023poster

Sequence generation applications require satisfying semantic constraints, such as ensuring that programs are correct, using certain keywords, or avoiding undesirable content. Language models, whether fine-tuned or prompted with few-shot demonstrations, frequently violate these constraints, and lack…

Cited by 122SourcePDFScholar
2023

Inference-Time Policy Adapters (IPA): Tailoring Extreme-Scale LMs without Fine-tuning

EMNLP 2023long main

While extreme-scale language models have demonstrated exceptional performance on a variety of language tasks, the degree of control over these language models through pure prompting can often be limited. Directly fine-tuning such language models can be effective for tailoring them, but it can be eit…

Cited by 0SourcecodeScholar
2023

STEER: Unified Style Transfer with Expert Reinforcement

EMNLP 2023long findings

While text style transfer has many applications across natural language processing, the core premise of transferring from a single source style is unrealistic in a real-world setting. In this work, we focus on arbitrary style transfer: rewriting a text from an arbitrary, unknown style to a target st…

Cited by 0SourcecodeScholar
2023

Self-Refine: Iterative Refinement with Self-Feedback

NeurIPS 2023poster

Like humans, large language models (LLMs) do not always generate the best output on their first try. Motivated by how humans refine their written text, we introduce Self-Refine, an approach for improving initial outputs from LLMs through iterative feedback and refinement. The main idea is to generat…

Cited by 1546SourcePDFScholar
2022

COLD Decoding: Energy-based Constrained Text Generation with Langevin Dynamics

NeurIPS 2022accept

Many applications of text generation require incorporating different constraints to control the semantics or style of generated text. These constraints can be hard (e.g., ensuring certain keywords are included in the output) and soft (e.g., contextualizing the output with the left- or right-hand con…

2022

Generated Knowledge Prompting for Commonsense Reasoning

ACL 2022long

It remains an open question whether incorporating external knowledge benefits commonsense reasoning while maintaining the flexibility of pretrained sequence models. To investigate this question, we develop generated knowledge prompting, which consists of generating knowledge from a language model, t…

2022

LILA: A Unified Benchmark for Mathematical Reasoning

EMNLP 2022main

Mathematical reasoning skills are essential for general-purpose intelligentsystems to perform tasks from grocery shopping to climate modeling.Towards evaluating and improving AI systems in this domain, we proposeLILA, a unified mathematical reasoning benchmark consisting of 23 diversetasks along fou…

2022

Maieutic Prompting: Logically Consistent Reasoning with Recursive Explanations

EMNLP 2022main

Pre-trained language models (LMs) struggle with consistent reasoning; recently, prompting LMs to generate explanations that self-guide the inference has emerged as a promising direction to amend this. However, these approaches are fundamentally bounded by the correctness of explanations, which thems…

Cited by 60SourcePDFScholar
2022

NaturalProver: Grounded Mathematical Proof Generation with Language Models

NeurIPS 2022accept

Theorem proving in natural mathematical language – the mixture of symbolic and natural language used by humans – plays a central role in mathematical advances and education, and tests aspects of reasoning that are core to intelligence. Yet it has remained underexplored with modern generative models.…

2022

NeuroLogic A*esque Decoding: Constrained Text Generation with Lookahead Heuristics

NAACL 2022long

The dominant paradigm for neural text generation is left-to-right decoding from autoregressive language models. Constrained or controllable generation under complex lexical constraints, however, requires foresight to plan ahead feasible future paths. Drawing inspiration from the A* search algorithm,…

2022

Prompt Waywardness: The Curious Case of Discretized Interpretation of Continuous Prompts

NAACL 2022long

Fine-tuning continuous prompts for target tasks has recently emerged as a compact alternative to full model fine-tuning. Motivated by these promising results, we investigate the feasibility of extracting a discrete (textual) interpretation of continuous prompts that is faithful to the problem they s…

2022

QUARK: Controllable Text Generation with Reinforced Unlearning

NeurIPS 2022accept

Large-scale language models often learn behaviors that are misaligned with user expectations. Generated text may contain offensive or toxic language, contain significant repetition, or be of a different sentiment than desired by the user. We consider the task of unlearning these misalignments by fin…

2022

Rainier: Reinforced Knowledge Introspector for Commonsense Question Answering

EMNLP 2022main

Knowledge underpins reasoning. Recent research demonstrates that when relevant knowledge is provided as additional context to commonsense question answering (QA), it can substantially enhance the performance even on top of state-of-the-art. The fundamental challenge is where and how to find such kno…

2022

Symbolic Brittleness in Sequence Models: On Systematic Generalization in Symbolic Mathematics

AAAI 2022technical

Neural sequence models trained with maximum likelihood estimation have led to breakthroughs in many tasks, where success is defined by the gap between training and test performance. However, their ability to achieve stronger forms of generalization remains unclear. We consider the problem of symboli…

2022

Symbolic Knowledge Distillation: from General Language Models to Commonsense Models

NAACL 2022long

The common practice for training commonsense models has gone from–human–to–corpus–to–machine: humans author commonsense knowledge graphs in order to train commonsense models. In this work, we investigate an alternative, from–machine–to–corpus–to–machine: general language models author these commonse…

2021

Divergence Frontiers for Generative Models: Sample Complexity, Quantization Effects, and Frontier Integrals

NeurIPS 2021poster

The spectacular success of deep generative models calls for quantitative tools to measure their statistical performance. Divergence frontiers have recently been proposed as an evaluation framework for generative models, due to their ability to measure the quality-diversity trade-off inherent to deep…

2021

MAUVE: Measuring the Gap Between Neural Text and Human Text using Divergence Frontiers

NeurIPS 2021oral

As major progress is made in open-ended text generation, measuring how close machine-generated text is to human language remains a critical open problem. We introduce Mauve, a comparison measure for open-ended text generation, which directly compares the learnt distribution from a text generation mo…

Cited by 355SourcePDFScholar
2021

MLE-Guided Parameter Search for Task Loss Minimization in Neural Sequence Modeling

AAAI 2021technical

Neural autoregressive sequence models are used to generate sequences in a variety of natural language processing (NLP) tasks, where they are evaluated according to sequence-level task losses. These models are typically trained with maximum likelihood estimation, which ignores the task loss, yet empi…

2021

NaturalProofs: Mathematical Theorem Proving in Natural Language

NeurIPS 2021poster

Understanding and creating mathematics using natural mathematical language - the mixture of symbolic and natural language used by humans - is a challenging and important problem for driving progress in machine learning. As a step in this direction, we develop NaturalProofs, a multi-domain corpus of…

Cited by 69SourcecodeScholar
2020

Neural Text Generation With Unlikelihood Training

ICLR 2020poster

Neural text generation is a key tool in natural language applications, but it is well known there are major problems at its core. In particular, standard likelihood training and decoding leads to dull and repetitive outputs. While some post-hoc fixes have been proposed, in particular top-k and nucle…

Cited by 622SourcecodeScholar
2018

Loss Functions for Multiset Prediction

NeurIPS 2018poster

We study the problem of multiset prediction. The goal of multiset prediction is to train a predictor that maps an input to a multiset consisting of multiple items. Unlike existing problems in supervised learning, such as classification, ranking and sequence generation, there is no known order among…

Cited by 24SourcePDFScholar
2017

Saliency-based Sequential Image Attention with Multiset Prediction

NeurIPS 2017poster

Humans process visual scenes selectively and sequentially using attention. Central to models of human visual attention is the saliency map. We propose a hierarchical visual architecture that operates on a saliency map and uses a novel attention mechanism to sequentially focus on salient regions and…

Cited by 27SourcePDFScholar