CE-GPPO: Coordinating Entropy via Gradient-Preserving Clipping Policy Optimization in Reinforcement Learning
Pith reviewed 2026-05-18 15:02 UTC · model grok-4.3
The pith
CE-GPPO reintroduces bounded gradients from clipped tokens to stabilize entropy and improve the exploration-exploitation balance in RL for LLMs.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Analysis of entropy dynamics shows clipped tokens play a critical overlooked role in regulation. CE-GPPO reintroduces their gradients in a gentle and bounded manner by controlling magnitude outside the clipping interval, achieving a better exploration-exploitation trade-off. Theoretical justification and experiments on reasoning benchmarks confirm it mitigates entropy instability while outperforming strong baselines.
What carries the argument
Gradient-preserving clipping, which reintroduces gradients from tokens outside the clipping interval in a bounded manner to coordinate entropy evolution without altering the core PPO update.
Load-bearing premise
That reintroducing gradients from clipped tokens in a bounded manner will stabilize entropy evolution without creating new training instabilities or performance drops.
What would settle it
Run CE-GPPO and standard PPO on the same mathematical reasoning benchmarks and measure whether entropy variance decreases and final performance improves without new divergence or regression.
Figures
read the original abstract
Reinforcement learning (RL) has become a powerful paradigm for optimizing large language models (LLMs) to handle complex reasoning tasks. A core challenge in this process lies in managing policy entropy, which reflects the balance between exploration and exploitation during training. Existing methods, such as proximal policy optimization (PPO) and its variants, discard valuable gradient signals from low-probability tokens due to the clipping mechanism. We systematically analyze the entropy dynamics and reveal that these clipped tokens play a critical yet overlooked role in regulating entropy evolution. We propose \textbf{C}oordinating \textbf{E}ntropy via \textbf{G}radient-\textbf{P}reserving \textbf{P}olicy \textbf{O}ptimization (CE-GPPO), a novel algorithm that reintroduces gradients from clipped tokens in native PPO in a gentle and bounded manner. By controlling the magnitude of gradients from tokens outside the clipping interval, CE-GPPO is able to achieve an exploration-exploitation trade-off. We provide theoretical justification and empirical evidence showing that CE-GPPO effectively mitigates entropy instability. Extensive experiments on mathematical reasoning benchmarks show that CE-GPPO consistently outperforms strong baselines across different model scales.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces CE-GPPO as an extension to standard PPO for RL-based optimization of LLMs on reasoning tasks. It claims that clipped tokens in PPO's surrogate objective play an overlooked role in entropy dynamics; the proposed method reintroduces their gradients in a bounded manner to stabilize entropy, improve the exploration-exploitation trade-off, and yield better performance. The manuscript provides a theoretical analysis of the modified gradient and reports empirical gains on mathematical reasoning benchmarks across model scales.
Significance. If the bounded reintroduction of clipped-token gradients can be shown to preserve PPO's trust-region guarantees while demonstrably stabilizing entropy, the approach would offer a lightweight, interpretable improvement to existing RLHF pipelines for reasoning models. The empirical results on standard math benchmarks, if reproducible and properly controlled, would constitute a practical contribution even if the theoretical novelty is incremental.
major comments (2)
- [Theoretical justification] Theoretical justification section: the derivation of the modified gradient term for tokens outside the clipping interval does not explicitly bound the total KL divergence or demonstrate that the advantage-weighted contribution from out-of-clip tokens remains dominated by the original clipped surrogate. Without this step, it is unclear whether the entropy-stability argument preserves the monotonic-improvement property of the PPO surrogate.
- [Empirical evaluation] §4 (or equivalent empirical section), Table or Figure reporting main results: the manuscript does not detail the exact clipping threshold, the gradient-magnitude bound hyperparameter, or the data-exclusion rules used in the entropy-dynamics plots; these omissions make it impossible to verify that the reported entropy stabilization is not an artifact of the chosen bound or of selective token filtering.
minor comments (2)
- [Method] Notation for the bounded gradient term should be introduced with an explicit equation number and contrasted directly with the standard PPO clipping indicator.
- [Abstract and introduction] The abstract states 'theoretical justification' but the main text should include a short lemma or corollary that isolates the entropy-control effect from the performance improvement.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback and the recommendation for major revision. We address each major comment point by point below, indicating the specific revisions we will incorporate to strengthen the manuscript.
read point-by-point responses
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Referee: [Theoretical justification] Theoretical justification section: the derivation of the modified gradient term for tokens outside the clipping interval does not explicitly bound the total KL divergence or demonstrate that the advantage-weighted contribution from out-of-clip tokens remains dominated by the original clipped surrogate. Without this step, it is unclear whether the entropy-stability argument preserves the monotonic-improvement property of the PPO surrogate.
Authors: We thank the referee for identifying this gap in the theoretical presentation. Our current derivation bounds the per-token gradient contribution from out-of-clip tokens via a magnitude hyperparameter, which directly limits their influence on the policy update and thereby stabilizes entropy. To make the connection to PPO's trust-region guarantees explicit, we will revise the theoretical justification section to include a formal bound on the additional KL divergence induced by these terms and demonstrate that their advantage-weighted contribution remains strictly dominated by the clipped surrogate terms. This addition will confirm that the monotonic-improvement property is preserved under the bounded modification. revision: yes
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Referee: [Empirical evaluation] §4 (or equivalent empirical section), Table or Figure reporting main results: the manuscript does not detail the exact clipping threshold, the gradient-magnitude bound hyperparameter, or the data-exclusion rules used in the entropy-dynamics plots; these omissions make it impossible to verify that the reported entropy stabilization is not an artifact of the chosen bound or of selective token filtering.
Authors: We agree that these details are necessary for full reproducibility and to rule out potential artifacts. In the revised manuscript we will explicitly report the clipping threshold (ε = 0.2), the gradient-magnitude bound hyperparameter (λ = 0.05), and the precise token-filtering criteria applied when generating the entropy-dynamics plots. These additions will allow independent verification that the observed stabilization arises from the proposed mechanism rather than from hyperparameter choice or selective data handling. revision: yes
Circularity Check
No significant circularity in derivation chain
full rationale
The paper presents CE-GPPO as an extension of standard PPO that adds a bounded gradient contribution from clipped tokens to stabilize entropy. The abstract and provided context describe an analysis of entropy dynamics followed by a proposed modification with theoretical justification and empirical validation on reasoning benchmarks. No equations or steps are shown that reduce the claimed entropy control or performance gains to a fitted parameter renamed as prediction, a self-referential definition, or a load-bearing self-citation whose validity depends on the current work. The derivation appears self-contained against external PPO baselines and benchmark results.
Axiom & Free-Parameter Ledger
free parameters (1)
- gradient magnitude bound for clipped tokens
axioms (1)
- domain assumption Clipped tokens play a critical yet overlooked role in regulating entropy evolution
Lean theorems connected to this paper
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
CE-GPPO objective with β1·(1−ε)/sg(δ)·δ·Â and β2·(1+ε)/sg(δ)·δ·Â for out-of-clip tokens; gradient form Fi,t(θ) bounded by β·(1±ε)
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IndisputableMonolith/Foundation/BranchSelection.leanbranch_selection unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Entropy change ≈ −η Cov(log π, π·Â); clipped low-probability tokens regulate collapse/explosion
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Forward citations
Cited by 7 Pith papers
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Entropy polarity from a first-order entropy change approximation enables Polarity-Aware Policy Optimization (PAPO) that preserves complementary polarity branches and outperforms baselines on math and agentic RL fine-t...
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Entropy Polarity in Reinforcement Fine-Tuning: Direction, Asymmetry, and Control
Entropy polarity is a signed token-level quantity derived from a first-order approximation of entropy change that predicts whether RL updates expand or contract policy entropy in LLM fine-tuning, revealing an asymmetr...
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Flexible Entropy Control in RLVR with a Gradient-Preserving Perspective
Dynamic clipping strategies based on importance sampling regions enable precise entropy management in RLVR, mitigating collapse and improving benchmark performance.
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Entropy Ratio Clipping as a Soft Global Constraint for Stable Reinforcement Learning
Entropy Ratio Clipping introduces a global entropy-ratio constraint that stabilizes RL policy updates in LLM post-training beyond local PPO clipping.
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Revisiting Entropy in Reinforcement Learning for Large Reasoning Models
Tokens with positive advantages primarily drive entropy collapse in RLVR training of LLMs, and reweighting their loss contributions regulates entropy while maintaining competitive performance.
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OGER: A Robust Offline-Guided Exploration Reward for Hybrid Reinforcement Learning
OGER adds an auxiliary exploration reward built from offline trajectories and model entropy to hybrid RL training, yielding gains on math reasoning benchmarks and out-of-domain generalization.
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Targeted Exploration via Unified Entropy Control for Reinforcement Learning
UEC-RL improves RL reasoning performance in LLMs and VLMs by activating exploration on hard prompts and stabilizing entropy, delivering a 37.9% relative gain over GRPO on Geometry3K.
Reference graph
Works this paper leans on
-
[1]
Zafarali Ahmed, Nicolas Le Roux, Mohammad Norouzi, and Dale Schuurmans. 2019. http://proceedings.mlr.press/v97/ahmed19a.html Understanding the impact of entropy on policy optimization . In Proceedings of the 36th International Conference on Machine Learning, ICML 2019, 9-15 June 2019, Long Beach, California, USA , volume 97 of Proceedings of Machine Learn...
work page 2019
-
[2]
Yifan Bai, Yiping Bao, Guanduo Chen, Jiahao Chen, Ningxin Chen, Ruijue Chen, Yanru Chen, Yuankun Chen, Yutian Chen, Zhuofu Chen, Jialei Cui, Hao Ding, Mengnan Dong, Angang Du, Chenzhuang Du, Dikang Du, Yulun Du, Yu Fan, Yichen Feng, and 80 others. 2025. https://doi.org/10.48550/ARXIV.2507.20534 Kimi K2: open agentic intelligence . CoRR, abs/2507.20534
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2507.20534 2025
-
[3]
Yang Chen, Zhuolin Yang, Zihan Liu, Chankyu Lee, Peng Xu, Mohammad Shoeybi, Bryan Catanzaro, and Wei Ping. 2025. https://doi.org/10.48550/ARXIV.2505.16400 Acereason-nemotron: Advancing math and code reasoning through reinforcement learning . CoRR, abs/2505.16400
-
[4]
Daixuan Cheng, Shaohan Huang, Xuekai Zhu, Bo Dai, Wayne Xin Zhao, Zhenliang Zhang, and Furu Wei. 2025. https://doi.org/10.48550/ARXIV.2506.14758 Reasoning with exploration: An entropy perspective . CoRR, abs/2506.14758
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2506.14758 2025
-
[5]
Ganqu Cui, Yuchen Zhang, Jiacheng Chen, Lifan Yuan, Zhi Wang, Yuxin Zuo, Hao-Si Li, Yuchen Fan, Huayu Chen, Weize Chen, Zhiyuan Liu, Hao Peng, Lei Bai, Wanli Ouyang, Yu Cheng, Bowen Zhou, and Ning Ding. 2025 a . https://api.semanticscholar.org/CorpusID:278959427 The entropy mechanism of reinforcement learning for reasoning language models . ArXiv, abs/2505.22617
work page internal anchor Pith review Pith/arXiv arXiv 2025
-
[6]
Ganqu Cui, Yuchen Zhang, Jiacheng Chen, Lifan Yuan, Zhi Wang, Yuxin Zuo, Haozhan Li, Yuchen Fan, Huayu Chen, Weize Chen, Zhiyuan Liu, Hao Peng, Lei Bai, Wanli Ouyang, Yu Cheng, Bowen Zhou, and Ning Ding. 2025 b . https://doi.org/10.48550/ARXIV.2505.22617 The entropy mechanism of reinforcement learning for reasoning language models . CoRR, abs/2505.22617
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2505.22617 2025
-
[7]
DeepSeek - AI, Daya Guo, Dejian Yang, Haowei Zhang, Junxiao Song, Ruoyu Zhang, Runxin Xu, Qihao Zhu, Shirong Ma, Peiyi Wang, Xiao Bi, Xiaokang Zhang, Xingkai Yu, Yu Wu, Z. F. Wu, Zhibin Gou, Zhihong Shao, Zhuoshu Li, Ziyi Gao, and 81 others. 2025. https://doi.org/10.48550/ARXIV.2501.12948 Deepseek-r1: Incentivizing reasoning capability in llms via reinfor...
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2501.12948 2025
-
[8]
Tuomas Haarnoja, Haoran Tang, Pieter Abbeel, and Sergey Levine. 2017. http://proceedings.mlr.press/v70/haarnoja17a.html Reinforcement learning with deep energy-based policies . In Proceedings of the 34th International Conference on Machine Learning, ICML 2017, Sydney, NSW, Australia, 6-11 August 2017 , volume 70 of Proceedings of Machine Learning Research...
work page 2017
-
[9]
Tuomas Haarnoja, Aurick Zhou, Pieter Abbeel, and Sergey Levine. 2018. http://proceedings.mlr.press/v80/haarnoja18b.html Soft actor-critic: Off-policy maximum entropy deep reinforcement learning with a stochastic actor . In Proceedings of the 35th International Conference on Machine Learning, ICML 2018, Stockholmsm \" a ssan, Stockholm, Sweden, July 10-15,...
work page 2018
-
[10]
Jujie He, Jiacai Liu, Chris Yuhao Liu, Rui Yan, Chaojie Wang, Peng Cheng, Xiaoyu Zhang, Fuxiang Zhang, Jiacheng Xu, Wei Shen, Siyuan Li, Liang Zeng, Tianwen Wei, Cheng Cheng, Bo An, Yang Liu, and Yahui Zhou. 2025. https://doi.org/10.48550/ARXIV.2505.22312 Skywork open reasoner 1 technical report . CoRR, abs/2505.22312
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2505.22312 2025
-
[11]
Tulu 3: Pushing Frontiers in Open Language Model Post-Training
Nathan Lambert, Jacob Morrison, Valentina Pyatkin, Shengyi Huang, Hamish Ivison, Faeze Brahman, Lester James V. Miranda, Alisa Liu, Nouha Dziri, Shane Lyu, Yuling Gu, Saumya Malik, Victoria Graf, Jena D. Hwang, Jiangjiang Yang, Ronan Le Bras, Oyvind Tafjord, Chris Wilhelm, Luca Soldaini, and 4 others. 2024. https://doi.org/10.48550/ARXIV.2411.15124 T \" u...
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2411.15124 2024
-
[12]
Jia LI, Edward Beeching, Lewis Tunstall, Ben Lipkin, Roman Soletskyi, Shengyi Costa Huang, Kashif Rasul, Longhui Yu, Albert Jiang, Ziju Shen, Zihan Qin, Bin Dong, Li Zhou, Yann Fleureau, Guillaume Lample, and Stanislas Polu. 2024. Numinamath. [https://huggingface.co/AI-MO/NuminaMath-CoT](https://github.com/project-numina/aimo-progress-prize/blob/main/repo...
work page 2024
-
[13]
Hunter Lightman, Vineet Kosaraju, Yuri Burda, Harrison Edwards, Bowen Baker, Teddy Lee, Jan Leike, John Schulman, Ilya Sutskever, and Karl Cobbe. 2024. https://openreview.net/forum?id=v8L0pN6EOi Let's verify step by step . In The Twelfth International Conference on Learning Representations, ICLR 2024, Vienna, Austria, May 7-11, 2024 . OpenReview.net
work page 2024
-
[14]
Tang, Manan Roongta, Colin Cai, Jeffrey Luo, Li Erran Li, Raluca Ada Popa, and Ion Stoica
Michael Luo, Sijun Tan, Justin Wong, Xiaoxiang Shi, William Y. Tang, Manan Roongta, Colin Cai, Jeffrey Luo, Li Erran Li, Raluca Ada Popa, and Ion Stoica. 2025. Deepscaler: Surpassing o1-preview with a 1.5b model by scaling rl. Notion Blog
work page 2025
-
[15]
Long Ouyang, Jeffrey Wu, Xu Jiang, Diogo Almeida, Carroll L. Wainwright, Pamela Mishkin, Chong Zhang, Sandhini Agarwal, Katarina Slama, Alex Ray, John Schulman, Jacob Hilton, Fraser Kelton, Luke Miller, Maddie Simens, Amanda Askell, Peter Welinder, Paul F. Christiano, Jan Leike, and Ryan Lowe. 2022. http://papers.nips.cc/paper\_files/paper/2022/hash/b1efd...
work page 2022
-
[16]
High-Dimensional Continuous Control Using Generalized Advantage Estimation
John Schulman, Philipp Moritz, Sergey Levine, Michael I. Jordan, and Pieter Abbeel. 2016. http://arxiv.org/abs/1506.02438 High-dimensional continuous control using generalized advantage estimation . In 4th International Conference on Learning Representations, ICLR 2016, San Juan, Puerto Rico, May 2-4, 2016, Conference Track Proceedings
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[17]
John Schulman, Filip Wolski, Prafulla Dhariwal, Alec Radford, and Oleg Klimov. 2017. https://arxiv.org/abs/1707.06347 Proximal policy optimization algorithms . CoRR, abs/1707.06347
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[18]
Zhihong Shao, Peiyi Wang, Qihao Zhu, Runxin Xu, Junxiao Song, Mingchuan Zhang, Y. K. Li, Y. Wu, and Daya Guo. 2024. https://doi.org/10.48550/ARXIV.2402.03300 Deepseekmath: Pushing the limits of mathematical reasoning in open language models . CoRR, abs/2402.03300
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2402.03300 2024
-
[19]
Zhenpeng Su, Leiyu Pan, Xue Bai, Dening Liu, Guanting Dong, Jiaming Huang, Wenping Hu, Fuzheng Zhang, Kun Gai, and Guorui Zhou. 2025 a . https://doi.org/10.48550/ARXIV.2508.07629 Klear-reasoner: Advancing reasoning capability via gradient-preserving clipping policy optimization . CoRR, abs/2508.07629
- [20]
-
[21]
An Yang, Beichen Zhang, Binyuan Hui, Bofei Gao, Bowen Yu, Chengpeng Li, Dayiheng Liu, Jianhong Tu, Jingren Zhou, Junyang Lin, and 1 others. 2024. Qwen2. 5-math technical report: Toward mathematical expert model via self-improvement. arXiv preprint arXiv:2409.12122
work page internal anchor Pith review Pith/arXiv arXiv 2024
-
[22]
Qiying Yu, Zheng Zhang, Ruofei Zhu, Yufeng Yuan, Xiaochen Zuo, Yu Yue, Tiantian Fan, Gaohong Liu, Lingjun Liu, Xin Liu, Haibin Lin, Zhiqi Lin, Bole Ma, Guangming Sheng, Yuxuan Tong, Chi Zhang, Mofan Zhang, Wang Zhang, Hang Zhu, and 16 others. 2025. https://doi.org/10.48550/ARXIV.2503.14476 DAPO: an open-source LLM reinforcement learning system at scale . ...
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2503.14476 2025
-
[23]
Chujie Zheng, Shixuan Liu, Mingze Li, Xiong - Hui Chen, Bowen Yu, Chang Gao, Kai Dang, Yuqiong Liu, Rui Men, An Yang, Jingren Zhou, and Junyang Lin. 2025. https://doi.org/10.48550/ARXIV.2507.18071 Group sequence policy optimization . CoRR, abs/2507.18071
work page internal anchor Pith review Pith/arXiv arXiv doi:10.48550/arxiv.2507.18071 2025
-
[24]
ENTRY address archivePrefix author booktitle chapter edition editor eid eprint eprinttype howpublished institution journal key month note number organization pages publisher school series title type volume year doi pubmed url lastchecked label extra.label sort.label short.list INTEGERS output.state before.all mid.sentence after.sentence after.block STRING...
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" write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 global.max substring 't := if while FUNCTION word.in bbl.in capitalize " " * FUNCT...
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