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Main Authors: Xiao, Quan, Chen, Tianyi
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2511.21056
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author Xiao, Quan
Chen, Tianyi
author_facet Xiao, Quan
Chen, Tianyi
contents Offline data selection and online self-refining generation, which enhance the data quality, are crucial steps in adapting large language models (LLMs) to specific downstream tasks. We tackle offline data selection and online self-refining generations through an optimization perspective. Specifically, bilevel data selection is used for offline data selection with respect to the validation dataset, and we treat online self-refining generation as a model adaptation step of selecting the model trained on current responses that best fits the validation data. Our framework offers a unified understanding of offline data selection and self-refining generation by assigning a learned data weight to each question and response, either explicitly or implicitly. For the first time, we theoretically demonstrate the effectiveness of the bilevel data selection framework and demonstrate its performance gains over unfiltered direct mixing baselines. By combining offline data with validation-weighted online generations, our method enhances fine-tuning performance. Experiments on quality enhancement and safety-aware LLM fine-tuning validate its effectiveness.
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id arxiv_https___arxiv_org_abs_2511_21056
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Unified Understanding of Offline Data Selection and Online Self-refining Generation for Post-training LLMs
Xiao, Quan
Chen, Tianyi
Machine Learning
Computation and Language
Optimization and Control
Offline data selection and online self-refining generation, which enhance the data quality, are crucial steps in adapting large language models (LLMs) to specific downstream tasks. We tackle offline data selection and online self-refining generations through an optimization perspective. Specifically, bilevel data selection is used for offline data selection with respect to the validation dataset, and we treat online self-refining generation as a model adaptation step of selecting the model trained on current responses that best fits the validation data. Our framework offers a unified understanding of offline data selection and self-refining generation by assigning a learned data weight to each question and response, either explicitly or implicitly. For the first time, we theoretically demonstrate the effectiveness of the bilevel data selection framework and demonstrate its performance gains over unfiltered direct mixing baselines. By combining offline data with validation-weighted online generations, our method enhances fine-tuning performance. Experiments on quality enhancement and safety-aware LLM fine-tuning validate its effectiveness.
title A Unified Understanding of Offline Data Selection and Online Self-refining Generation for Post-training LLMs
topic Machine Learning
Computation and Language
Optimization and Control
url https://arxiv.org/abs/2511.21056