CLAIJul 9, 2025

FlexOlmo: Open Language Models for Flexible Data Use

AI2
arXiv:2507.07024v410 citationsh-index: 48
Originality Highly original
AI Analysis

This provides a solution for data owners and researchers in regulated industries with sensitive data, enabling use of closed data while respecting privacy and access controls.

The paper tackles the problem of training language models on closed datasets without data sharing by introducing FlexOlmo, a mixture-of-experts model that allows independent training and flexible inference, resulting in a 41% relative improvement on downstream tasks and outperforming prior methods by 10.1%.

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 closed datasets, and (2) data-flexible inference, where these parameters along with their associated data can be flexibly included or excluded from model inferences with no further training. FlexOlmo employs a mixture-of-experts (MoE) architecture where each expert is trained independently on closed datasets and later integrated through a new domain-informed routing without any joint training. FlexOlmo is trained on FlexMix, a corpus we curate comprising publicly available datasets alongside seven domain-specific sets, representing realistic approximations of closed sets. We evaluate models with up to 37 billion parameters (20 billion active) on 31 diverse downstream tasks. We show that a general expert trained on public data can be effectively combined with independently trained experts from other data owners, leading to an average 41% relative improvement while allowing users to opt out of certain data based on data licensing or permission requirements. Our approach also outperforms prior model merging methods by 10.1% on average and surpasses the standard MoE trained without data restrictions using the same training FLOPs. Altogether, this research presents a solution for both data owners and researchers in regulated industries with sensitive or protected data. FlexOlmo enables benefiting from closed data while respecting data owners' preferences by keeping their data local and supporting fine-grained control of data access during inference.

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