arXiv:2409.05358cs.LGcs.AI2024-09ICLR被引 3

提出统一框架,让内在动机与奖励塑形更安全可靠。

BAMDP Shaping: a Unified Framework for Intrinsic Motivation and Reward Shaping

  • 将伪奖励统一为贝叶斯自适应马尔可夫决策过程中的奖励塑形
  • 证明特定伪奖励函数可避免奖励黑客攻击,提升探索效率
  • 适用于元强化学习和普通强化学习,适合研究探索与奖励设计的学者

内在动机与奖励塑形通过添加伪奖励引导强化学习(RL)智能体,可能催生有用行为,但也可能导致有害利用,如沉迷于噪声电视屏幕。本文提供一个理论模型,预测此类行为,并给出可限制负面效应的通用条件。将所有伪奖励视为贝叶斯自适应马尔可夫决策过程(BAMDP)中的奖励塑形,该过程将学习问题建模为对智能体知识状态的马尔可夫决策过程。最优探索最大化BAMDP状态价值,其分解为信息获取价值与物理状态先验价值。伪奖励通过激励提升这两类价值的行为来引导智能体,当其与实际价值不匹配时则阻碍探索。本文将基于势能的塑形理论扩展至BAMDP,证明了贝叶斯自适应势能函数(BAMPFs)在元强化学习中免疫奖励黑客攻击,并实证显示其帮助元强化学习智能体在伯努利老虎机任务中学习出最优算法。进一步证明,具有有界单调递增势能的BAMPFs在标准强化学习设置中也抵抗奖励黑客攻击。方法易于改造或设计新伪奖励项,已在Mountain Car环境中验证有效。

原文摘要 · Abstract (English)

Intrinsic motivation and reward shaping guide reinforcement learning (RL) agents by adding pseudo-rewards, which can lead to useful emergent behaviors. However, they can also encourage counterproductive exploits, e.g., fixation with noisy TV screens. Here we provide a theoretical model which anticipates these behaviors, and provides broad criteria under which adverse effects can be bounded. We characterize all pseudo-rewards as reward shaping in Bayes-Adaptive Markov Decision Processes (BAMDPs), which formulates the problem of learning in MDPs as an MDP over the agent's knowledge. Optimal exploration maximizes BAMDP state value, which we decompose into the value of the information gathered and the prior value of the physical state. Psuedo-rewards guide RL agents by rewarding behavior that increases these value components, while they hinder exploration when they align poorly with the actual value. We extend potential-based shaping theory to prove BAMDP Potential-based shaping Functions (BAMPFs) are immune to reward-hacking (convergence to behaviors maximizing composite rewards to the detriment of real rewards) in meta-RL, and show empirically how a BAMPF helps a meta-RL agent learn optimal RL algorithms for a Bernoulli Bandit domain. We finally prove that BAMPFs with bounded monotone increasing potentials also resist reward-hacking in the regular RL setting. We show that it is straightforward to retrofit or design new pseudo-reward terms in this form, and provide an empirical demonstration in the Mountain Car environment.

强化学习奖励塑形内在动机元学习

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