Text-based games present a unique class of sequential decision making problem in which agents interact with a partially observable, simulated environment via actions and observations conveyed through natural language. Such observations typically include instructions that, in a reinforcement learning (RL) setting, can directly or indirectly guide a player towards completing reward-worthy tasks. In this work, we study the ability of RL agents to follow such instructions. We conduct experiments that show that the performance of state-of-the-art text-based game agents is largely unaffected by the presence or absence of such instructions, and that these agents are typically unable to execute tasks to completion. To further study and address the task of instruction following, we equip RL agents with an internal structured representation of natural language instructions in the form of Linear Temporal Logic (LTL), a formal language that is increasingly used for temporally extended reward specification in RL. Our framework both supports and highlights the benefit of understanding the temporal semantics of instructions and in measuring progress towards achievement of such a temporally extended behaviour. Experiments with 500+ games in TextWorld demonstrate the superior performance of our approach.

为了解决艰巨的任务，人类提出问题以从外部来源获取知识。相反，经典的加强学习者缺乏这种能力，并且常常诉诸探索性行为。这会加剧，因为很少的当今环境支持查询知识。为了研究如何通过语言教授代理来查询外部知识，我们首先介绍了两个新环境：基于网格世界的Q-babyai和基于文本的Q-Textworld。除了物理互动外，代理还可以查询专门针对这些环境的外部知识源来收集信息。其次，我们提出了“寻求知识”（AFK）代理，该代理学会生成语言命令以查询有助于解决任务的有意义的知识。 AFK利用非参数记忆，指针机制和情节探索奖金来解决（1）无关的信息，（2）一个较大的查询语言空间，（3）延迟奖励有意义的查询。广泛的实验表明，AFK代理在具有挑战性的Q-Babyai和Q-Textworld环境方面优于最近的基线。

Transformer, originally devised for natural language processing, has also attested significant success in computer vision. Thanks to its super expressive power, researchers are investigating ways to deploy transformers to reinforcement learning (RL) and the transformer-based models have manifested their potential in representative RL benchmarks. In this paper, we collect and dissect recent advances on transforming RL by transformer (transformer-based RL or TRL), in order to explore its development trajectory and future trend. We group existing developments in two categories: architecture enhancement and trajectory optimization, and examine the main applications of TRL in robotic manipulation, text-based games, navigation and autonomous driving. For architecture enhancement, these methods consider how to apply the powerful transformer structure to RL problems under the traditional RL framework, which model agents and environments much more precisely than deep RL methods, but they are still limited by the inherent defects of traditional RL algorithms, such as bootstrapping and "deadly triad". For trajectory optimization, these methods treat RL problems as sequence modeling and train a joint state-action model over entire trajectories under the behavior cloning framework, which are able to extract policies from static datasets and fully use the long-sequence modeling capability of the transformer. Given these advancements, extensions and challenges in TRL are reviewed and proposals about future direction are discussed. We hope that this survey can provide a detailed introduction to TRL and motivate future research in this rapidly developing field.

基于自动机的方法使机器人能够执行各种复杂的任务。但是，大多数现有的基于自动机的算法都高度依赖于已考虑任务的状态的手动定制表示，从而限制了其在深度强化学习算法中的适用性。为了解决这个问题，通过将变压器纳入强化学习中，我们开发了一个双转化器引导的时间逻辑框架（T2TL），该逻辑框架（T2TL）两次利用变压器的结构特征，即首先通过变压器模块编码LTL指令，以有效地理解对有效的理解培训期间的任务说明，然后再次通过变压器编码上下文变量，以改善任务性能。特别是，LTL指令由Co-Safe LTL指定。作为具有语义的改写操作，LTL的进展被利用以将复杂的任务分解为可学习的子目标，这不仅将非马克维亚奖励决策转换为马尔可夫的奖励决策过程，而且通过同时学习多个子 - 学习效率，提高了采样效率。任务。进一步纳入了环境不足的LTL预训练方案，以促进变压器模块的学习，从而改善LTL的表示。模拟和实验结果证明了T2TL框架的有效性。

文本冒险游戏由于其组合大的动作空间和稀疏奖励而导致加强学习方法具有独特的挑战。这两个因素的相互作用尤为苛刻，因为大型动作空间需要广泛的探索，而稀疏奖励提供有限的反馈。这项工作提出使用多级方法来解决探索 - 与利用困境，该方法明确地解除了每一集中的这两种策略。我们的算法称为Exploit-Dear-Descore（XTX），使用剥削策略开始每个剧集，该策略是从过去的一组有希望的轨迹开始，然后切换到旨在发现导致未经看不见状态空间的新动作的探索政策。该政策分解允许我们将全球决策结合在该空间中返回基于好奇的本地探索的全球决策，这是由人类可能接近这些游戏的情况。我们的方法在杰里科基准（Hausknecht等人，2020）中，在杰里科基准（Hausknecht等人，2020）中，在确定性和随机设置的比赛中显着优于27％和11％的平均正常化分数。在Zork1的游戏中，特别是，XTX获得103的得分，超过先前方法的2倍改善，并且在游戏中推过已经困扰先前的方法的游戏中的几个已知的瓶颈。

Real-world reinforcement learning tasks often involve some form of partial observability where the observations only give a partial or noisy view of the true state of the world. Such tasks typically require some form of memory, where the agent has access to multiple past observations, in order to perform well. One popular way to incorporate memory is by using a recurrent neural network to access the agent's history. However, recurrent neural networks in reinforcement learning are often fragile and difficult to train, susceptible to catastrophic forgetting and sometimes fail completely as a result. In this work, we propose Deep Transformer Q-Networks (DTQN), a novel architecture utilizing transformers and self-attention to encode an agent's history. DTQN is designed modularly, and we compare results against several modifications to our base model. Our experiments demonstrate the transformer can solve partially observable tasks faster and more stably than previous recurrent approaches.

Adequately assigning credit to actions for future outcomes based on their contributions is a long-standing open challenge in Reinforcement Learning. The assumptions of the most commonly used credit assignment method are disadvantageous in tasks where the effects of decisions are not immediately evident. Furthermore, this method can only evaluate actions that have been selected by the agent, making it highly inefficient. Still, no alternative methods have been widely adopted in the field. Hindsight Credit Assignment is a promising, but still unexplored candidate, which aims to solve the problems of both long-term and counterfactual credit assignment. In this thesis, we empirically investigate Hindsight Credit Assignment to identify its main benefits, and key points to improve. Then, we apply it to factored state representations, and in particular to state representations based on the causal structure of the environment. In this setting, we propose a variant of Hindsight Credit Assignment that effectively exploits a given causal structure. We show that our modification greatly decreases the workload of Hindsight Credit Assignment, making it more efficient and enabling it to outperform the baseline credit assignment method on various tasks. This opens the way to other methods based on given or learned causal structures.

Reinforcement Learning (RL) is a popular machine learning paradigm where intelligent agents interact with the environment to fulfill a long-term goal. Driven by the resurgence of deep learning, Deep RL (DRL) has witnessed great success over a wide spectrum of complex control tasks. Despite the encouraging results achieved, the deep neural network-based backbone is widely deemed as a black box that impedes practitioners to trust and employ trained agents in realistic scenarios where high security and reliability are essential. To alleviate this issue, a large volume of literature devoted to shedding light on the inner workings of the intelligent agents has been proposed, by constructing intrinsic interpretability or post-hoc explainability. In this survey, we provide a comprehensive review of existing works on eXplainable RL (XRL) and introduce a new taxonomy where prior works are clearly categorized into model-explaining, reward-explaining, state-explaining, and task-explaining methods. We also review and highlight RL methods that conversely leverage human knowledge to promote learning efficiency and performance of agents while this kind of method is often ignored in XRL field. Some challenges and opportunities in XRL are discussed. This survey intends to provide a high-level summarization of XRL and to motivate future research on more effective XRL solutions. Corresponding open source codes are collected and categorized at https://github.com/Plankson/awesome-explainable-reinforcement-learning.

安全探索是强化学习（RL）的常见问题，旨在防止代理在探索环境时做出灾难性的决定。一个解决这个问题的方法家庭以这种环境的（部分）模型的形式假设域知识，以决定动作的安全性。所谓的盾牌迫使RL代理只选择安全的动作。但是，要在各种应用中采用，必须超越执行安全性，还必须确保RL的适用性良好。我们通过与最先进的深度RL的紧密整合扩展了盾牌的适用性，并在部分可观察性下提供了充满挑战的，稀疏的奖励环境中的广泛实证研究。我们表明，经过精心整合的盾牌可确保安全性，并可以提高RL代理的收敛速度和最终性能。我们此外表明，可以使用盾牌来引导最先进的RL代理：它们在屏蔽环境中初步学习后保持安全，从而使我们最终可以禁用潜在的过于保守的盾牌。

Linear temporal logic (LTL) is a widely-used task specification language which has a compositional grammar that naturally induces temporally extended behaviours across tasks, including conditionals and alternative realizations. An important problem i RL with LTL tasks is to learn task-conditioned policies which can zero-shot generalize to new LTL instructions not observed in the training. However, because symbolic observation is often lossy and LTL tasks can have long time horizon, previous works can suffer from issues such as training sampling inefficiency and infeasibility or sub-optimality of the found solutions. In order to tackle these issues, this paper proposes a novel multi-task RL algorithm with improved learning efficiency and optimality. To achieve the global optimality of task completion, we propose to learn options dependent on the future subgoals via a novel off-policy approach. In order to propagate the rewards of satisfying future subgoals back more efficiently, we propose to train a multi-step value function conditioned on the subgoal sequence which is updated with Monte Carlo estimates of multi-step discounted returns. In experiments on three different domains, we evaluate the LTL generalization capability of the agent trained by the proposed method, showing its advantage over previous representative methods.

强化学习（RL）是人工智能中的核心问题。这个问题包括定义可以通过与环境交互学习最佳行为的人工代理 - 其中，在代理试图最大化的奖励信号的奖励信号中定义最佳行为。奖励机（RMS）提供了一种基于Automate的基于自动机的表示，该奖励功能使RL代理能够将RL问题分解为可以通过禁止策略学习有效地学习的结构化子问题。在这里，我们表明可以从经验中学习RMS，而不是由用户指定，并且可以使用所产生的问题分解来有效地解决部分可观察的RL问题。我们将学习RMS的任务作为离散优化问题构成，其中目标是找到将问题分解为一组子问题的RM，使得其最佳记忆策略的组合是原始问题的最佳策略。我们展示了这种方法在三个部分可观察的域中的有效性，在那里它显着优于A3C，PPO和宏碁，并讨论其优点，限制和更广泛的潜力。

众所周知，在漫长的地平线和稀疏的奖励任务中，加强学习（RL）是困难的，需要大量的培训步骤。加快该过程的标准解决方案是利用额外的奖励信号，将其塑造以更好地指导学习过程。在语言条件的RL的背景下，语言输入的抽象和概括属性为更有效地塑造奖励的方式提供了机会。在本文中，我们利用这一想法并提出了一种自动奖励塑形方法，代理商从一般语言目标中提取辅助目标。这些辅助目标使用问题生成（QG）和问题答案（QA）系统：它们包括导致代理商尝试使用其自己的轨迹重建有关全球目标的部分信息的问题。当它成功时，它会获得与对答案的信心成正比的内在奖励。这激励代理生成轨迹，这些轨迹明确解释了一般语言目标的各个方面。我们的实验研究表明，这种方法不需要工程师干预来设计辅助目标，可以通过有效指导探索来提高样品效率。

解决时间扩展的任务是大多数增强学习（RL）算法的挑战[ARXIV：1906.07343]。我们研究了RL代理商学会提出自然语言问题的能力，以了解其环境并在新颖，时间扩展的环境中实现更大的概括性能。我们通过赋予该代理商的能力向全知的甲骨文提出“是，不”问题来做到这一点。这使代理商可以获得有关手头任务的指导，同时限制了对新信息的访问。为了在时间扩展的任务的背景下研究这种自然语言问题的出现，我们首先在迷你网格环境中训练代理商。然后，我们将受过训练的代理转移到另一个更艰难的环境中。与无法提出问题的基线代理相比，我们观察到概括性能的显着提高。通过将其对自然语言在其环境中的理解，代理可以推理其环境的动态，以至于在新型环境中部署时可以提出新的，相关的问题。

马尔可夫决策过程通常用于不确定性下的顺序决策。然而，对于许多方面，从受约束或安全规范到任务和奖励结构中的各种时间（非Markovian）依赖性，需要扩展。为此，近年来，兴趣已经发展成为强化学习和时间逻辑的组合，即灵活的行为学习方法的组合，具有稳健的验证和保证。在本文中，我们描述了最近引入的常规决策过程的实验调查，该过程支持非马洛维亚奖励功能以及过渡职能。特别是，我们为常规决策过程，与在线，增量学习有关的算法扩展，对无模型和基于模型的解决方案算法的实证评估，以及以常规但非马尔维亚，网格世界的应用程序的算法扩展。

深度强化学习（RL）的进展是通过用于培训代理商的具有挑战性的基准的可用性来驱动。但是，社区广泛采用的基准未明确设计用于评估RL方法的特定功能。虽然存在用于评估RL的特定打开问题的环境（例如探索，转移学习，无监督环境设计，甚至语言辅助RL），但一旦研究超出证明，通常难以将这些更富有，更复杂的环境 - 概念结果。我们展示了一个强大的沙箱框架，用于易于设计新颖的RL环境。 Minihack是一个停止商店，用于RL实验，环境包括从小房间到复杂的，程序生成的世界。通过利用来自Nethack的全套实体和环境动态，MiniHack是最富有的基网上的视频游戏之一，允许设计快速方便的定制RL测试台。使用这种沙箱框架，可以轻松设计新颖的环境，可以使用人类可读的描述语言或简单的Python接口来设计。除了各种RL任务和基线外，Minihack还可以包装现有的RL基准，并提供无缝添加额外复杂性的方法。

Deep reinforcement learning is poised to revolutionise the field of AI and represents a step towards building autonomous systems with a higher level understanding of the visual world. Currently, deep learning is enabling reinforcement learning to scale to problems that were previously intractable, such as learning to play video games directly from pixels. Deep reinforcement learning algorithms are also applied to robotics, allowing control policies for robots to be learned directly from camera inputs in the real world. In this survey, we begin with an introduction to the general field of reinforcement learning, then progress to the main streams of value-based and policybased methods. Our survey will cover central algorithms in deep reinforcement learning, including the deep Q-network, trust region policy optimisation, and asynchronous advantage actor-critic. In parallel, we highlight the unique advantages of deep neural networks, focusing on visual understanding via reinforcement learning. To conclude, we describe several current areas of research within the field.

在这项工作中，我们提出并评估了一种新的增强学习方法，紧凑体验重放（编者），它使用基于相似转换集的复发的预测目标值的时间差异学习，以及基于两个转换的经验重放的新方法记忆。我们的目标是减少在长期累计累计奖励的经纪人培训所需的经验。它与强化学习的相关性与少量观察结果有关，即它需要实现类似于文献中的相关方法获得的结果，这通常需要数百万视频框架来培训ATARI 2600游戏。我们举报了在八个挑战街机学习环境（ALE）挑战游戏中，为仅10万帧的培训试验和大约25,000次迭代的培训试验中报告了培训试验。我们还在与基线的同一游戏中具有相同的实验协议的DQN代理呈现结果。为了验证从较少数量的观察结果近似于良好的政策，我们还将其结果与从啤酒的基准上呈现的数百万帧中获得的结果进行比较。

在过去的十年中，多智能经纪人强化学习（Marl）已经有了重大进展，但仍存在许多挑战，例如高样本复杂性和慢趋同稳定的政策，在广泛的部署之前需要克服，这是可能的。然而，在实践中，许多现实世界的环境已经部署了用于生成策略的次优或启发式方法。一个有趣的问题是如何最好地使用这些方法作为顾问，以帮助改善多代理领域的加强学习。在本文中，我们提供了一个原则的框架，用于将动作建议纳入多代理设置中的在线次优顾问。我们描述了在非传记通用随机游戏环境中提供多种智能强化代理（海军上将）的问题，并提出了两种新的基于Q学习的算法：海军上将决策（海军DM）和海军上将 - 顾问评估（Admiral-AE） ，这使我们能够通过适当地纳入顾问（Admiral-DM）的建议来改善学习，并评估顾问（Admiral-AE）的有效性。我们从理论上分析了算法，并在一般加上随机游戏中提供了关于他们学习的定点保证。此外，广泛的实验说明了这些算法：可以在各种环境中使用，具有对其他相关基线的有利相比的性能，可以扩展到大状态行动空间，并且对来自顾问的不良建议具有稳健性。

We present a retrospective on the state of Embodied AI research. Our analysis focuses on 13 challenges presented at the Embodied AI Workshop at CVPR. These challenges are grouped into three themes: (1) visual navigation, (2) rearrangement, and (3) embodied vision-and-language. We discuss the dominant datasets within each theme, evaluation metrics for the challenges, and the performance of state-of-the-art models. We highlight commonalities between top approaches to the challenges and identify potential future directions for Embodied AI research.

深度加强学习概括（RL）的研究旨在产生RL算法，其政策概括为在部署时间进行新的未经调整情况，避免对其培训环境的过度接受。如果我们要在现实世界的情景中部署强化学习算法，那么解决这一点至关重要，那么环境将多样化，动态和不可预测。该调查是这个新生领域的概述。我们为讨论不同的概括问题提供统一的形式主义和术语，在以前的作品上建立不同的概括问题。我们继续对现有的基准进行分类，以及用于解决泛化问题的当前方法。最后，我们提供了对现场当前状态的关键讨论，包括未来工作的建议。在其他结论之外，我们认为，采取纯粹的程序内容生成方法，基准设计不利于泛化的进展，我们建议快速在线适应和将RL特定问题解决作为未来泛化方法的一些领域，我们推荐在UniTexplorated问题设置中构建基准测试，例如离线RL泛化和奖励函数变化。