Leverage the Average: an Analysis of KL Regularization in RL
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Abstract (arXiv)
Recent Reinforcement Learning (RL) algorithms making use of Kullback-Leibler (KL) regularization as a core component have shown outstanding performance. Yet, only little is understood theoretically about why KL regularization helps, so far. We study KL regularization within an approximate value iteration scheme and show that it implicitly averages q-values. Leveraging this insight, we provide a very strong performance bound, the very first to combine two desirable aspects: a linear dependency to the horizon (instead of quadratic) and an error propagation term involving an averaging effect of the estimation errors (instead of an accumulation effect). We also study the more general case of an additional entropy regularizer. The resulting abstract scheme encompasses many existing RL algorithms. Some of our assumptions do not hold with neural networks, so we complement this theoretical analysis with an extensive empirical study.
Key facts. Cited by 33 papers in the map (data through 7 Oct 2026). First posted on arXiv 31 Mar 2020.
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Citing papers per year: 2021: 12; 2022: 5; 2023: 5; 2024: 3; 2025: 4; 2026: 4.
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- 2021Maximum Entropy RL (Provably) Solves Some Robust RL Problemscited by 169
- 2023Extreme Q-Learning: MaxEnt RL without Entropycited by 113
- 2021Muesli: Combining Improvements in Policy Optimizationcited by 53
- 2024Correlated Proxies: A New Definition and Improved Mitigation for Reward Hackingcited by 50
- 2021Adversarially Guided Actor-Criticcited by 47
- 2023Towards Minimax Optimality of Model-based Robust Reinforcement Learningcited by 21
- 2021Improved Regret Bound and Experience Replay in Regularized Policy Iterationcited by 18
- 2021Bayesian Bellman Operatorscited by 16
- 2021Co-Adaptation of Algorithmic and Implementational Innovations in Inference-based Deep Reinforcement Learningcited by 15
- 2022Latent State Marginalization as a Low-cost Approach for Improving Explorationcited by 13
- 2025Mitigating Forgetting in LLM Fine-Tuning via Low-Perplexity Token Learningcited by 12
- 2021Optimization Issues in KL-Constrained Approximate Policy Iterationcited by 10
21 more
- 2021Implicitly Regularized RL with Implicit Q-Valuescited by 9
- 2022Lazy-MDPs: Towards Interpretable Reinforcement Learning by Learning When to Actcited by 7
- 2022Do You Need the Entropy Reward (in Practice)?cited by 6
- 2024q-exponential family for policy optimizationcited by 2
- 2025Non-Asymptotic Global Convergence of PPO-Clipcited by 2
- 2021Near Optimal Policy Optimization via REPScited by 1
- 2023Generalized Munchausen Reinforcement Learning using Tsallis KL Divergencecited by 1
- 2023Guaranteed Trust Region Optimization via Two-Phase KL Penalizationcited by 1
- 2024Dual Approximation Policy Optimizationcited by 1
- 2025On the Effect of Regularization in Policy Mirror Descentcited by 1
- 2026GeMPO: Generalized Measure Matching for Online Diffusion Reinforcement Learningcited by 1
- 2026Value Mirror Descent for Reinforcement Learningcited by 1
- 2026Abstention as an Action Can Kill Both the Reward Gradient and the KL Anchor: Collapse Law and Repair for Error-Penalized Reinforcement Learningcited by 1
- 2021Cautious Policy Programming: Exploiting KL Regularization in Monotonic Policy Improvement for Reinforcement Learningcited by 0
- 2021Error Controlled Actor-Criticcited by 0
- 2021Actor Loss of Soft Actor Critic Explainedcited by 0
- 2022q-Munchausen Reinforcement Learningcited by 0
- 2022Enforcing KL Regularization in General Tsallis Entropy Reinforcement Learning via Advantage Learningcited by 0
- 2023Acceleration in Policy Optimizationcited by 0
- 2025Symmetric Behavior Regularized Policy Optimizationcited by 0
- 2026Deconstructing Actor-Critic: A Large-scale Empirical Study of Design Components for Practitionerscited by 0
- 2026Abstention as an Action Can Kill Both the Reward Gradient and the KL Anchor: Collapse Law and Repair for Error-Penalized Reinforcement Learning31 Jul 2026
- 2026Deconstructing Actor-Critic: A Large-scale Empirical Study of Design Components for Practitioners14 Jul 2026
- 2026Value Mirror Descent for Reinforcement Learning7 Apr 2026
- 2026GeMPO: Generalized Measure Matching for Online Diffusion Reinforcement Learning10 Mar 2026
- 2025Non-Asymptotic Global Convergence of PPO-Clip18 Dec 2025
- 2025Symmetric Behavior Regularized Policy Optimization6 Aug 2025
- 2025On the Effect of Regularization in Policy Mirror Descent11 Jul 2025
- 2025Mitigating Forgetting in LLM Fine-Tuning via Low-Perplexity Token Learning24 Jan 2025
- 2024Dual Approximation Policy Optimization2 Oct 2024
- 2024q-exponential family for policy optimization14 Aug 2024
- 2024Correlated Proxies: A New Definition and Improved Mitigation for Reward Hacking5 Mar 2024
- 2023Guaranteed Trust Region Optimization via Two-Phase KL Penalization8 Dec 2023
21 more
- 2023Acceleration in Policy Optimization18 Jun 2023
- 2023Towards Minimax Optimality of Model-based Robust Reinforcement Learning10 Feb 2023
- 2023Generalized Munchausen Reinforcement Learning using Tsallis KL Divergence27 Jan 2023
- 2023Extreme Q-Learning: MaxEnt RL without Entropy5 Jan 2023
- 2022Latent State Marginalization as a Low-cost Approach for Improving Exploration3 Oct 2022
- 2022Enforcing KL Regularization in General Tsallis Entropy Reinforcement Learning via Advantage Learning16 May 2022
- 2022q-Munchausen Reinforcement Learning16 May 2022
- 2022Lazy-MDPs: Towards Interpretable Reinforcement Learning by Learning When to Act16 Mar 2022
- 2022Do You Need the Entropy Reward (in Practice)?28 Jan 2022
- 2021Actor Loss of Soft Actor Critic Explained31 Dec 2021
- 2021Error Controlled Actor-Critic6 Sep 2021
- 2021Implicitly Regularized RL with Implicit Q-Values16 Aug 2021
- 2021Cautious Policy Programming: Exploiting KL Regularization in Monotonic Policy Improvement for Reinforcement Learning13 Jul 2021
- 2021Bayesian Bellman Operators9 Jun 2021
- 2021Muesli: Combining Improvements in Policy Optimization13 Apr 2021
- 2021Co-Adaptation of Algorithmic and Implementational Innovations in Inference-based Deep Reinforcement Learning31 Mar 2021
- 2021Near Optimal Policy Optimization via REPS17 Mar 2021
- 2021Maximum Entropy RL (Provably) Solves Some Robust RL Problems10 Mar 2021
- 2021Improved Regret Bound and Experience Replay in Regularized Policy Iteration25 Feb 2021
- 2021Optimization Issues in KL-Constrained Approximate Policy Iteration11 Feb 2021
- 2021Adversarially Guided Actor-Critic8 Feb 2021
- 2023Extreme Q-Learning: MaxEnt RL without Entropycited by 113
- 2025Symmetric Behavior Regularized Policy Optimizationcited by 0
- 2025Symmetric Behavior Regularized Policy Optimization6 Aug 2025
- 2023Extreme Q-Learning: MaxEnt RL without Entropy5 Jan 2023
- 2021Maximum Entropy RL (Provably) Solves Some Robust RL Problemscited by 169
- 2021Muesli: Combining Improvements in Policy Optimizationcited by 53
- 2021Adversarially Guided Actor-Criticcited by 47
- 2023Towards Minimax Optimality of Model-based Robust Reinforcement Learningcited by 21
- 2021Improved Regret Bound and Experience Replay in Regularized Policy Iterationcited by 18
- 2021Bayesian Bellman Operatorscited by 16
- 2021Co-Adaptation of Algorithmic and Implementational Innovations in Inference-based Deep Reinforcement Learningcited by 15
- 2022Latent State Marginalization as a Low-cost Approach for Improving Explorationcited by 13
- 2021Optimization Issues in KL-Constrained Approximate Policy Iterationcited by 10
- 2021Implicitly Regularized RL with Implicit Q-Valuescited by 9
- 2022Lazy-MDPs: Towards Interpretable Reinforcement Learning by Learning When to Actcited by 7
- 2022Do You Need the Entropy Reward (in Practice)?cited by 6
12 most cited of 28 All 28 (JSON)
- 2026Abstention as an Action Can Kill Both the Reward Gradient and the KL Anchor: Collapse Law and Repair for Error-Penalized Reinforcement Learning31 Jul 2026
- 2026Deconstructing Actor-Critic: A Large-scale Empirical Study of Design Components for Practitioners14 Jul 2026
- 2026Value Mirror Descent for Reinforcement Learning7 Apr 2026
- 2025Non-Asymptotic Global Convergence of PPO-Clip18 Dec 2025
- 2025On the Effect of Regularization in Policy Mirror Descent11 Jul 2025
- 2024Dual Approximation Policy Optimization2 Oct 2024
- 2024q-exponential family for policy optimization14 Aug 2024
- 2023Guaranteed Trust Region Optimization via Two-Phase KL Penalization8 Dec 2023
- 2023Acceleration in Policy Optimization18 Jun 2023
- 2023Towards Minimax Optimality of Model-based Robust Reinforcement Learning10 Feb 2023
- 2023Generalized Munchausen Reinforcement Learning using Tsallis KL Divergence27 Jan 2023
- 2022Latent State Marginalization as a Low-cost Approach for Improving Exploration3 Oct 2022
12 newest of 28 All 28 (JSON)