In constrained reinforcement learning (RL), a learning agent seeks to not only optimize the overall reward but also satisfy the additional safety, diversity, or budget constraints. Consequently, existing constrained RL solutions require several new algorithmic ingredients that are notably different from standard RL. On the other hand, reward-free RL is independently developed in the unconstrained literature, which learns the transition dynamics without using the reward information, and thus naturally capable of addressing RL with multiple objectives under the common dynamics. This paper bridges reward-free RL and constrained RL. Particularly, we propose a simple meta-algorithm such that given any reward-free RL oracle, the approachability and constrained RL problems can be directly solved with negligible overheads in sample complexity. Utilizing the existing reward-free RL solvers, our framework provides sharp sample complexity results for constrained RL in the tabular MDP setting, matching the best existing results up to a factor of horizon dependence; our framework directly extends to a setting of tabular two-player Markov games, and gives a new result for constrained RL with linear function approximation.

本文探讨奖励自由强化学习和受限制的强化学习之间的联系，在标记MDP设置中，我们提出了一种简单的元算法，利用现有的奖励自由RL解算器，对受限制的强化学习问题进行直接求解， 在现有结果的基础上匹配最佳结果，同时在线性函数近似下，我们直接将其扩展到标记二人马尔可夫博弈的设置中，并提供了一个新的受限制的RL结果。

基于约束的强化学习的简单无回报方法