Large Language Models

OPUS: Towards Efficient and Principled Data Selection in Large Language Model Pre-training in Every Iteration

SShaobo WangXXuan OuyangTTianyi XuYYuzheng HuJJialin LiuGGuo ChenTTianyu ZhangJJunhao ZhengKKexin YangXXingzhang RenDDayiheng LiuLLinfeng Zhang
Published
February 5, 2026
Authors
12
Word Count
38,572

Dynamic data selection aligned with optimizer geometry for efficient language model pre-training.

Abstract

As high-quality public text approaches exhaustion, a phenomenon known as the Data Wall, pre-training is shifting from more tokens to better tokens. However, existing methods either rely on heuristic static filters that ignore training dynamics, or use dynamic yet optimizer-agnostic criteria based on raw gradients. We propose OPUS (Optimizer-induced Projected Utility Selection), a dynamic data selection framework that defines utility in the optimizer-induced update space. OPUS scores candidates by projecting their effective updates, shaped by modern optimizers, onto a target direction derived from a stable, in-distribution proxy. To ensure scalability, we employ Ghost technique with CountSketch for computational efficiency, and Boltzmann sampling for data diversity, incurring only 4.7\% additional compute overhead. OPUS achieves remarkable results across diverse corpora, quality tiers, optimizers, and model scales. In pre-training of GPT-2 Large/XL on FineWeb and FineWeb-Edu with 30B tokens, OPUS outperforms industrial-level baselines and even full 200B-token training. Moreover, when combined with industrial-level static filters, OPUS further improves pre-training efficiency, even with lower-quality data. Furthermore, in continued pre-training of Qwen3-8B-Base on SciencePedia, OPUS achieves superior performance using only 0.5B tokens compared to full training with 3B tokens, demonstrating significant data efficiency gains in specialized domains.

Key Takeaways

  • 1

    OPUS selects training data dynamically by scoring in the optimizer's actual geometry rather than raw gradients.

  • 2

    Static data filtering cannot adapt to changing model needs throughout training, making dynamic selection essential.

  • 3

    Redundancy penalties prevent repeated selection of similar samples, improving diversity and training efficiency.

Limitations

  • OPUS requires computing preconditioners for specific optimizers like AdamW and Muon, limiting generalizability.

  • Scaling OPUS to massive datasets demands significant engineering complexity and computational overhead.

Keywords

data selectionoptimizer-induced update spaceeffective updatesstable in-distribution proxyGhost techniqueCountSketchBoltzmann samplingpre-trainingGPT-2Qwen3-8B-BaseFineWebFineWeb-EduSciencePedia

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OPUS: Towards Efficient and Principled Data Selection in Large Language Model Pre-training in Every Iteration | Paperchime