提出新优化器AdamO,解决离线强化学习中值函数崩溃问题。
AdamO: A Collapse-Suppressed Optimizer for Offline RL

- 从控制论角度建模离线TD学习,发现优化器自身会引发不稳定性。
- 设计带正交约束的AdamO,使参数更新更稳定,提升算法成功率。
- 适用于多种离线强化学习框架,显著改善训练稳定性和性能表现。
离线强化学习在使用基于时序差分(TD)的更新时可能因误差放大而导致价值函数崩溃,产生极端且无用的Q值。本文的关键洞察是:崩溃不仅是备份规则或网络架构的问题,优化器动态本身也能直接引发或抑制不稳定性。从控制理论视角出发,将离线TD学习建模为反馈系统,并分析基于Adam的批评者更新。由此推导出局部更新动态稳定的充要条件:对应更新算子的谱半径严格小于1。进一步分析表明,标准Adam更新可能无意中扭曲参数几何结构,因此提出显式正交性约束以防止TD误差放大。为此,我们提出AdamO,一种基于Adam但具有解耦正交性修正的优化器,其修正受严格任务对齐预算调控。理论上证明该设计可保证最坏情况下的任务安全性,并保留Adam的连续时间耗散动力学特性。实验上,AdamO与多种离线强化学习基线广泛兼容,在多个基准测试中均提升了稳定性与回报。
原文摘要 · Abstract (English)
Offline reinforcement learning (RL) can fail spectacularly when bootstrapped temporal-difference (TD) updates amplify their own errors, driving the critic toward extreme and unusable Q-values. A key counterintuitive insight of this work is that collapse is not only a property of the backup rule or network architecture: optimizer dynamics themselves can directly trigger or suppress instability. From a control-theoretic viewpoint, we model offline TD learning as a feedback system and analyze Adam-based critic updates. This yields a necessary and sufficient condition for stability of the induced local update dynamics: within the regime we analyze, these dynamics are stable if and only if the spectral radius of the corresponding update operator is strictly below one. Further analysis suggests that standard Adam updates can inadvertently distort the parameter geometry, motivating explicit orthogonality constraints to prevent TD error amplification. To this end, we propose AdamO, an Adam-based optimizer with a decoupled orthogonality correction regulated by a strict task-alignment budget. We prove that this design theoretically guarantees worst-case task safety and preserves Adam's continuous-time dissipative dynamics. Empirically, AdamO is broadly compatible with diverse offline RL baselines, improving stability and returns across a broad suite of benchmarks.
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