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Model-Based Reinforcement Learning (MBRL) has shown promise in visual control tasks due to its data efficiency. However, training MBRL agents to develop generalizable perception remains challenging, especially amid visual distractions that introduce noise in representation learning. We introduce Segmentation Dreamer (SD), a framework that facilitates representation learning in MBRL by incorporating a novel auxiliary task. Assuming that task-relevant components in images can be easily identified with prior knowledge in a given task, SD uses segmentation masks on image observations to reconstruct only task-relevant regions, reducing representation complexity. SD can leverage either ground-truth masks available in simulation or potentially imperfect segmentation foundation models. The latter is further improved by selectively applying the image reconstruction loss to mitigate misleading learning signals from mask prediction errors. In modified DeepMind Control suite and Meta-World tasks with added visual distractions, SD achieves significantly better sample efficiency and greater final performance than prior work and is especially effective in sparse reward tasks that had been unsolvable by prior work. We also validate its effectiveness in a real-world robotic lane-following task when training with intentional distractions for zero-shot transfer.a 

While Deep Reinforcement Learning (DRL) has achieved remarkable success across various domains, it remains vulnerable to occasional catastrophic failures without additional safeguards. An effective solution to prevent these failures is to use a shield that validates and adjusts the agent’s actions to ensure compliance with a provided set of safety specifications. For real-world robotic domains, it is essential to define safety specifications over continuous state and action spaces to accurately account for system dynamics and compute new actions that minimally deviate from the agent’s original decision. In this paper, we present the first shielding approach specifically designed to ensure the satisfaction of safety requirements in continuous state and action spaces, making it suitable for practical robotic applications. Our method builds upon realizability, an essential property that confirms the shield will always be able to generate a safe action for any state in the environment. We formally prove that realizability can be verified for stateful shields, enabling the incorporation of non-Markovian safety requirements, such as loop avoidance. Finally, we demonstrate the effectiveness of our approach in ensuring safety without compromising the policy’s success rate by applying it to a navigation problem and a multi-agent particle environment1. Keywords: Shielding, Reinforcement Learning, Safety, Robotics 

This paper focuses on the computational complexity of computing empirical plug-in estimates for causal effect queries. Given a causal graph and observational data, any identifiable causal query can be estimated from an expression over the observed variables, called the estimand. The estimand can then be evaluated by plugging in probabilities computed empirically from data. In contrast to conventional wisdom which assumes that high dimensional probabilistic functions will lead to exponential evaluation time, we show that estimand evaluation can be done efficiently, potentially in time linear in the data size, depending on the estimand's hypergraph. In particular, we show that both the treewidth and hypertree width of the estimand's structure bound the evaluation complexity, analogous to their role in bounding the complexity of inference in probabilistic graphical models. In settings with high dimensional functions, the hypertree width often provides a more effective bound, since the empirical distributions are sparse.