让智能体按方向而非目标位置行动,提升在线目标导向强化学习性能。
Direction-Conditioned Policies via Compositional Subgoal Scoring for Online Goal-Conditioned Reinforcement Learning

- 将目标分解为方向与距离,用统一表示学习共享信息。
- 在9个环境中优于对比式RL,尤其在操作和障碍交互任务中提升显著。
- 理论证明方向足够性,且可定位失败原因,适合复杂环境部署。
哈密顿-雅可比-贝尔曼理论表明,最优目标导向动作仅依赖于当前状态到目标的梯度,而非原始目标本身——后者在目标远离数据分布时几何意义弱。本文提出方向条件策略(DCP),一种全在线方法:先通过子目标评分选择与目标对齐的状态 $z_t$,再用单位方向 $d_t$ 与距离 $r_t$ 来指导动作。两者共享一个 InfoNCE 表示 $ψ$,联合训练,部署时仅保留方向条件,子目标评分移除,接口可独立修改。我们证明三点:第一,在控制仿射动态下,方向足以决定最优动作;第二,在合理表示假设下,训练与部署的输入误差可控;第三,给出方向条件失效的可控制子空间特征。在9个环境中,DCP 多数指标优于对比式强化学习,尤其在操作和障碍交互任务中提升明显;可视化显示 $ψ$ 距离结构呈现环境拓扑的准度量特性,唯一失败案例(AntSoccer)对应学习梯度异常,符合理论预期。
原文摘要 · Abstract (English)
Hamilton-Jacobi-Bellman theory implies that the optimal goal-conditioned action depends on the goal only through the gradient of the goal-reaching distance at the current state, yet standard online GCRL still conditions the actor on the raw goal -- a signal that is geometrically uninformative when the goal is far from the data distribution. We propose Direction-Conditioned Policies (DCP), a fully online method that decomposes goal-reaching into two components sharing one InfoNCE representation $ψ$: a subgoal-scoring step that selects a visited state $z_t$ aligned with the final goal $g$ in $ψ_g$, and a direction-conditioned actor that consumes the unit direction $d_t$ and magnitude $r_t$ from $ψ(s_t)$ to $ψ(z_t)$. The two components train jointly, factor cleanly at deployment (subgoal scoring is removed, while direction conditioning remains with $g$ in place of $z_t$), and admit independent modification at the same $(d_t,r_t)$ interface. We prove three results. First, direction sufficiency under HJB: the optimal action under control-affine dynamics depends on the goal only through the value gradient. Second, a quantitative bound showing that, under mild conditions on the learned representation and assuming the scoring rule returns an on-path $z_t$, the actor's conditioning input at training and at deployment coincide up to representation error and geodesic slack. Third, a controllable-subspace characterization of when directional conditioning fails. Across nine environments, DCP improves over Contrastive RL on most final metrics, with the largest gains on manipulation and obstacle-interaction tasks; a qualitative analysis of the learned $ψ$-distance landscape shows the contrastive representation behaves as an online quasimetric encoding environment topology, and the single failure case (AntSoccer) localizes to a learned-gradient pathology that the theory anticipates.
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