Principled RL for Flow Matching Emerges from the Chunk-level Policy Optimization

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Hauptverfasser: Luo, Yifu, Sun, Haoyuan, Hu, Xinhao, Du, Penghui, Fan, Keyu, Li, Bo, Du, Sinan, Wan, Xu, Chen, Zhiyu, Xia, Bo, Zhang, Tiantian, Chang, Yongzhe, Yu, Changqian, Gai, Kun, Wang, Xueqian
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Veröffentlicht: 2025
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author Luo, Yifu
Sun, Haoyuan
Hu, Xinhao
Du, Penghui
Fan, Keyu
Li, Bo
Du, Sinan
Wan, Xu
Chen, Zhiyu
Xia, Bo
Zhang, Tiantian
Chang, Yongzhe
Yu, Changqian
Gai, Kun
Wang, Xueqian
author_facet Luo, Yifu
Sun, Haoyuan
Hu, Xinhao
Du, Penghui
Fan, Keyu
Li, Bo
Du, Sinan
Wan, Xu
Chen, Zhiyu
Xia, Bo
Zhang, Tiantian
Chang, Yongzhe
Yu, Changqian
Gai, Kun
Wang, Xueqian
contents Recent Progress in post-training flow matching for text-to-image (T2I) generation with Group Relative Policy Optimization (GRPO) has demonstrated strong potential. However, it is hindered by a critical limitation: inaccurate advantage attribution. In this work, we argue that aggregating consecutive steps into a coherent `chunk' and shifting the policy optimization paradigm from GRPO's step level to the chunk level can effectively mitigate the negative impact of this issue. Building on this insight, we propose Group Chunking Policy Optimization (GCPO), the first chunk-level reinforcement learning approach for post-training flow matching. Extensive experiments demonstrate that GCPO achieves superior performance on both standard T2I benchmarks and preference alignment, with up to 43% relative gains over GRPO, highlighting the promise of chunk-level policy optimization. The code is available on https://github.com/xingzhejun/GCPO.
format Preprint
id arxiv_https___arxiv_org_abs_2510_21583
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Principled RL for Flow Matching Emerges from the Chunk-level Policy Optimization
Luo, Yifu
Sun, Haoyuan
Hu, Xinhao
Du, Penghui
Fan, Keyu
Li, Bo
Du, Sinan
Wan, Xu
Chen, Zhiyu
Xia, Bo
Zhang, Tiantian
Chang, Yongzhe
Yu, Changqian
Gai, Kun
Wang, Xueqian
Computer Vision and Pattern Recognition
Artificial Intelligence
Recent Progress in post-training flow matching for text-to-image (T2I) generation with Group Relative Policy Optimization (GRPO) has demonstrated strong potential. However, it is hindered by a critical limitation: inaccurate advantage attribution. In this work, we argue that aggregating consecutive steps into a coherent `chunk' and shifting the policy optimization paradigm from GRPO's step level to the chunk level can effectively mitigate the negative impact of this issue. Building on this insight, we propose Group Chunking Policy Optimization (GCPO), the first chunk-level reinforcement learning approach for post-training flow matching. Extensive experiments demonstrate that GCPO achieves superior performance on both standard T2I benchmarks and preference alignment, with up to 43% relative gains over GRPO, highlighting the promise of chunk-level policy optimization. The code is available on https://github.com/xingzhejun/GCPO.
title Principled RL for Flow Matching Emerges from the Chunk-level Policy Optimization
topic Computer Vision and Pattern Recognition
Artificial Intelligence
url https://arxiv.org/abs/2510.21583