LSPO: Length-aware Dynamic Sampling for Policy Optimization in LLM Reasoning

Fuente: arXiv
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Auteurs principaux: Chen, Weizhe, Koenig, Sven, Dilkina, Bistra
Format: Preprint
Publié: 2025
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author Chen, Weizhe
Koenig, Sven
Dilkina, Bistra
author_facet Chen, Weizhe
Koenig, Sven
Dilkina, Bistra
contents Since the release of Deepseek-R1, reinforcement learning with verifiable rewards (RLVR) has become a central approach for training large language models (LLMs) on reasoning tasks. Recent work has largely focused on modifying loss functions to make RLVR more efficient and effective. In this paper, motivated by studies of overthinking in LLMs, we propose Length-aware Sampling for Policy Optimization (LSPO), a novel meta-RLVR algorithm that dynamically selects training data at each step based on the average response length. We evaluate LSPO across multiple base models and datasets, demonstrating that it consistently improves learning effectiveness. In addition, we conduct a detailed ablation study to examine alternative ways of incorporating length signals into dynamic sampling, offering further insights and highlighting promising directions for future research.
format Preprint
id arxiv_https___arxiv_org_abs_2510_01459
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle LSPO: Length-aware Dynamic Sampling for Policy Optimization in LLM Reasoning
Chen, Weizhe
Koenig, Sven
Dilkina, Bistra
Machine Learning
Computation and Language
Since the release of Deepseek-R1, reinforcement learning with verifiable rewards (RLVR) has become a central approach for training large language models (LLMs) on reasoning tasks. Recent work has largely focused on modifying loss functions to make RLVR more efficient and effective. In this paper, motivated by studies of overthinking in LLMs, we propose Length-aware Sampling for Policy Optimization (LSPO), a novel meta-RLVR algorithm that dynamically selects training data at each step based on the average response length. We evaluate LSPO across multiple base models and datasets, demonstrating that it consistently improves learning effectiveness. In addition, we conduct a detailed ablation study to examine alternative ways of incorporating length signals into dynamic sampling, offering further insights and highlighting promising directions for future research.
title LSPO: Length-aware Dynamic Sampling for Policy Optimization in LLM Reasoning
topic Machine Learning
Computation and Language
url https://arxiv.org/abs/2510.01459