Adaptive curricula in reinforcement learning (RL) have proven effective for
producing policies robust to discrepancies between the train and test
environment. Recently, the Unsupervised Environment Design (UED) framework
generalized RL curricula to generating sequences of entire environments,
leading to new methods with robust minimax regret properties. Problematically,
in partially-observable or stochastic settings, optimal policies may depend on
the ground-truth distribution over aleatoric parameters of the environment in
the intended deployment setting, while curriculum learning necessarily shifts
the training distribution. We formalize this phenomenon as curriculum-induced
covariate shift (CICS), and describe how its occurrence in aleatoric parameters
can lead to suboptimal policies. Directly sampling these parameters from the
ground-truth distribution avoids the issue, but thwarts curriculum learning. We
propose SAMPLR, a minimax regret UED method that optimizes the ground-truth
utility function, even when the underlying training data is biased due to CICS.
We prove, and validate on challenging domains, that our approach preserves
optimality under the ground-truth distribution, while promoting robustness
across the full range of environment settings.

SAMLR 是一种适应性课程学习方法，可以在避免课程诱导的协变量漂移的情况下优化环境序列，保证在真实环境下最大化效用函数，实现强化学习中的最小后悔策略。