連続制御のための反復Gumbelプランニング
Iterative Gumbel Planning for Continuous Control
探索ベース計画と連続ガウス方策の不整合を解消するため、次元ごとの因子化カテゴリ方策とGumbel Top-Kサンプリング、MPPI型反復探索を組み合わせたIGPを提案し、DMControlとHumanoidBenchで最先端性能を達成した。
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著者: Shaohuai Liu, Weirui Ye, Yilun Du, Le Xie
分類: cs.LG, cs.AI
原文アブストラクト
Search-based planning remains a powerful policy improvement paradigm in reinforcement learning, driving milestone successes in discrete domains. However, extending this paradigm to continuous control exposes a structural mismatch: search evaluates a finite set of action candidates, whereas continuous RL typically relies on Gaussian policies. We show that winner-action distillation into a continuous Gaussian induces a \textit{projection error} and a stepwise variance-expanding gradient tendency when the selected action is sufficiently far from the current mean. Empirically, this tendency is associated with elevated terminal variance and a return gap on the evaluated tasks. To address this, we propose \textbf{Iterative Gumbel Planning (IGP)}. By adopting a per-dimension factorized categorical policy, IGP naturally aligns the policy support with the search candidates, eliminating the projection error and reducing the residual approximation to a bounded discretization error. To bypass the combinatorial explosion of high-dimensional discrete action spaces, IGP pairs Gumbel Top-$K$ candidate sampling with an MPPI-style multi-round iterative search to refine the policy at each state. Empirically, IGP achieves state-of-the-art aggregate performance and sample efficiency on DMControl and HumanoidBench. Furthermore, it produces more stable action sequences with lower temporal variance, demonstrating its practical potential for real-world robotic deployment.