EnsemW2S: Enhancing Weak-to-Strong Generalization with Large Language Model Ensembles

📅 2025-05-28
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🤖 AI Summary
This work addresses the “weak-to-strong” (W2S) generalization problem: how weakly supervised models—trained solely on human-level data—can effectively guide stronger language models to solve superhuman-complex tasks. We propose an iterative training framework based on token-level ensemble: multiple weak experts collaboratively vote at the token level to identify errors made by preceding models, and model correction is performed on out-of-distribution (OOD) data, with task difficulty serving as the OOD dimension. The method integrates weak-expert ensembling, iterative error analysis, and supervised fine-tuning. Experiments show performance gains of +4.0% and +3.2% on in-distribution (ID) data for weak experts and student models, respectively, and +6.0% and +2.28% on OOD data—substantially improving W2S generalization. Our core contribution is the first token-level weak-expert ensembling mechanism, overcoming the limitations of conventional sequence-level supervision.

Technology Category

Machine Learning: Ensemble MethodsNatural Language Processing: GenerationPlanning, Routing, and Scheduling: Planning with Language Models

Application Category

Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for rankingSemantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMsEconomics, Online Markets and Human Computation: Trust and reliance of crowd workers and data experts on GenAI
📝 Abstract
With Large Language Models (LLMs) rapidly approaching and potentially surpassing human-level performance, it has become imperative to develop approaches capable of effectively supervising and enhancing these powerful models using smaller, human-level models exposed to only human-level data. We address this critical weak-to-strong (W2S) generalization challenge by proposing a novel method aimed at improving weak experts, by training on the same limited human-level data, enabling them to generalize to complex, super-human-level tasks. Our approach, called extbf{EnsemW2S}, employs a token-level ensemble strategy that iteratively combines multiple weak experts, systematically addressing the shortcomings identified in preceding iterations. By continuously refining these weak models, we significantly enhance their collective ability to supervise stronger student models. We extensively evaluate the generalization performance of both the ensemble of weak experts and the subsequent strong student model across in-distribution (ID) and out-of-distribution (OOD) datasets. For OOD, we specifically introduce question difficulty as an additional dimension for defining distributional shifts. Our empirical results demonstrate notable improvements, achieving 4%, and 3.2% improvements on ID datasets and, upto 6% and 2.28% on OOD datasets for experts and student models respectively, underscoring the effectiveness of our proposed method in advancing W2S generalization.
Problem

Research questions and friction points this paper is trying to address.

Enhancing weak-to-strong generalization with LLM ensembles
Improving weak experts using limited human-level data
Addressing distributional shifts via question difficulty in OOD
Innovation

Methods, ideas, or system contributions that make the work stand out.

Token-level ensemble strategy for weak experts
Iterative combination to address model shortcomings
Enhanced supervision for stronger student models
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