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arXiv · 2508.12116

DynamixSFT: Dynamic Mixture Optimization of Instruction Tuning Collections

Haebin Shin·Lei Ji·Xiao Liu·Zhiwei Yu·Hyunwoo Yoo·Qi Chen·Yeyun Gong
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Abstract

As numerous instruction-tuning datasets continue to emerge, dynamically balancing and optimizing their mixtures has become a critical challenge. To address this, we propose DynamixSFT, a dynamic and automated method for instruction-tuning dataset mixture optimization. We formulate the problem as a multi-armed bandit setup and introduce a Prior-scaled Boltzmann Exploration that softly anchors the updated sampling distribution to the original dataset proportions, thereby preserving the inherent diversity and coverage of the collection. Sampling probabilities are updated using a lightweight 1-Step Look-ahead Reward, reflecting how much the dataset contributes to improving the model's performance at its current state. We demonstrate that DynamixSFT effectively optimizes the Tulu-2-mixture and Tulu-3-mixture collections across 10 benchmarks, while introducing minimal computational overhead over naive sampling. Furthermore, we provide a comprehensive analysis and visualizations to offer deeper insights into the adaptive dynamics of our method.

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Haebin Shin, Lei Ji, Xiao Liu, Zhiwei Yu, Hyunwoo Yoo, Qi Chen, Yeyun Gong. 2025-08-16. DynamixSFT: Dynamic Mixture Optimization of Instruction Tuning Collections. https://doi.org/10.18653/v1%2F2026.findings-acl.1972

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