GRPO's group-mean baseline assigns identical advantages to all tokens under output-only rewards, inducing gradient sparsity and an intrinsic rank-2 structure proven from the zero-sum constraint and confirmed by SVD on Nemotron-4B gradients.
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High-Dimensional Continuous Control Using Generalized Advantage Estimation
Mixed citation behavior. Most common role is background (47%).
abstract
Policy gradient methods are an appealing approach in reinforcement learning because they directly optimize the cumulative reward and can straightforwardly be used with nonlinear function approximators such as neural networks. The two main challenges are the large number of samples typically required, and the difficulty of obtaining stable and steady improvement despite the nonstationarity of the incoming data. We address the first challenge by using value functions to substantially reduce the variance of policy gradient estimates at the cost of some bias, with an exponentially-weighted estimator of the advantage function that is analogous to TD(lambda). We address the second challenge by using trust region optimization procedure for both the policy and the value function, which are represented by neural networks. Our approach yields strong empirical results on highly challenging 3D locomotion tasks, learning running gaits for bipedal and quadrupedal simulated robots, and learning a policy for getting the biped to stand up from starting out lying on the ground. In contrast to a body of prior work that uses hand-crafted policy representations, our neural network policies map directly from raw kinematics to joint torques. Our algorithm is fully model-free, and the amount of simulated experience required for the learning tasks on 3D bipeds corresponds to 1-2 weeks of real time.
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- abstract Policy gradient methods are an appealing approach in reinforcement learning because they directly optimize the cumulative reward and can straightforwardly be used with nonlinear function approximators such as neural networks. The two main challenges are the large number of samples typically required, and the difficulty of obtaining stable and steady improvement despite the nonstationarity of the incoming data. We address the first challenge by using value functions to substantially reduce the variance of policy gradient estimates at the cost of some bias, with an exponentially-weighted estimat
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representative citing papers
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citing papers explorer
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On the Policy Gradient Foundations of Group Relative Policy Optimization: Credit Assignment, Gradient Sparsity, and Rank Collapse
GRPO's group-mean baseline assigns identical advantages to all tokens under output-only rewards, inducing gradient sparsity and an intrinsic rank-2 structure proven from the zero-sum constraint and confirmed by SVD on Nemotron-4B gradients.
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AtomComposer: Discovering Chemical Space from First Principles with Reinforcement Learning
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Agent-BRACE: Decoupling Beliefs from Actions in Long-Horizon Tasks via Verbalized State Uncertainty
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Mirror Descent Beyond Euclidean Stability: An Exponential Separation in Initialization Sensitivity
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TriSearch: Learning to Optimize Triangulations via Bistellar Flips
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Bridging Atomistic Simulation and Experimental Processing Timescales with Goal-Directed Deep Reinforcement Learning
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Policy Optimization in Hybrid Discrete-Continuous Action Spaces via Mixed Gradients
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Self-Supervised On-Policy Reinforcement Learning via Contrastive Proximal Policy Optimisation
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Adaptive Smooth Tchebycheff Attention for Multi-Objective Policy Optimization
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Adaptive TD-Lambda for Cooperative Multi-agent Reinforcement Learning
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Metric-Gradient Projection for Stable Multi-Agent Policy Learning
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Learning with a Single Rollout via Monte Carlo Pass@k Critic
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Heuresis: Search Strategies for Autonomous AI Research Agents Across Quality, Diversity and Novelty
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Reinforcement Learning Enables Autonomous Microrobot Navigation and Intervention in Simulated Blood Capillaries
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