分层增强学习中的选项框架将整体目标分解为选项或更简单的任务和相关策略的组合，从而可以在动作领域进行抽象。理想情况下，可以在不同的高级目标中重复使用这些选择；确实，这种重复使用对于实现可以有效利用其先前经验的持续学习代理的愿景是必要的。先前的方法仅提出了将预科选项转移到新任务设置的有限形式。我们提出了一种新颖的选项索引方法，用于分层学习（OI-HRL），在该方法中，我们学习选项与环境中存在的项目之间的亲和力功能。这使我们能够通过将目标指导的学习仅限于与手头的任务相关的那些选项，在测试时间零弹性概括中有效地重用大量的经过预告片的选项库。我们开发了一个元训练循环，该循环通过结合有关检索期权与高级目标的相关性的反馈来了解一系列HRL问题的选项和环境的表示。我们在两个模拟设置中评估了OI -HRL -Craftworld和AI2THOR环境 - 并表明我们与Oracular Baseline达到了性能竞争，并且比基线的实质性取得了可观的增长，该基线具有可用于学习层次结构策略的整个选项库。

实践和磨练技能构成了人类学习方式的基本组成部分，但很少专门培训人造代理人来执行它们。取而代之的是，它们通常是端到端训练的，希望有用的技能将被隐含地学习，以最大程度地提高某些外部奖励功能的折扣回报。在本文中，我们研究了如何将技能纳入具有较大州行动空间和稀疏奖励的复杂环境中的加固学习训练中。为此，我们创建了Skillhack，这是Nethack游戏的任务和相关技能的基准。我们评估了该基准测试的许多基准，以及我们自己的新型基于技能的方法层次启动（HKS），该方法的表现优于所有其他评估的方法。我们的实验表明，先验了解有用技能的学习可以显着改善代理在复杂问题上的表现。我们最终认为，利用预定义的技能为RL问题提供了有用的归纳偏见，尤其是那些具有较大国家行动空间和稀疏奖励的问题。

我们提出了一种层次结构的增强学习方法Hidio，可以以自我监督的方式学习任务不合时宜的选项，同时共同学习利用它们来解决稀疏的奖励任务。与当前倾向于制定目标的低水平任务或预定临时的低级政策不同的层次RL方法不同，Hidio鼓励下级选项学习与手头任务无关，几乎不需要假设或很少的知识任务结构。这些选项是通过基于选项子对象的固有熵最小化目标来学习的。博学的选择是多种多样的，任务不可能的。在稀疏的机器人操作和导航任务的实验中，Hidio比常规RL基准和两种最先进的层次RL方法，其样品效率更高。

Hierarchical methods in reinforcement learning have the potential to reduce the amount of decisions that the agent needs to perform when learning new tasks. However, finding a reusable useful temporal abstractions that facilitate fast learning remains a challenging problem. Recently, several deep learning approaches were proposed to learn such temporal abstractions in the form of options in an end-to-end manner. In this work, we point out several shortcomings of these methods and discuss their potential negative consequences. Subsequently, we formulate the desiderata for reusable options and use these to frame the problem of learning options as a gradient-based meta-learning problem. This allows us to formulate an objective that explicitly incentivizes options which allow a higher-level decision maker to adjust in few steps to different tasks. Experimentally, we show that our method is able to learn transferable components which accelerate learning and performs better than existing prior methods developed for this setting. Additionally, we perform ablations to quantify the impact of using gradient-based meta-learning as well as other proposed changes.

Meta-Renifiltive学习（Meta-RL）已被证明是利用事先任务的经验，以便快速学习新的相关任务的成功框架，但是，当前的Meta-RL接近在稀疏奖励环境中学习的斗争。尽管现有的Meta-RL算法可以学习适应新的稀疏奖励任务的策略，但是使用手形奖励功能来学习实际适应策略，或者需要简单的环境，其中随机探索足以遇到稀疏奖励。在本文中，我们提出了对Meta-RL的后视抢购的制定，该rl抢购了在Meta培训期间的经验，以便能够使用稀疏奖励完全学习。我们展示了我们的方法在套件挑战稀疏奖励目标达到的环境中，以前需要密集的奖励，以便在Meta训练中解决。我们的方法使用真正的稀疏奖励功能来解决这些环境，性能与具有代理密集奖励功能的培训相当。

我们开发了一种新的持续元学习方法，以解决连续多任务学习中的挑战。在此设置中，代理商的目标是快速通过任何任务序列实现高奖励。先前的Meta-Creenifiltive学习算法已经表现出有希望加速收购新任务的结果。但是，他们需要在培训期间访问所有任务。除了简单地将过去的经验转移到新任务，我们的目标是设计学习学习的持续加强学习算法，使用他们以前任务的经验更快地学习新任务。我们介绍了一种新的方法，连续的元策略搜索（Comps），通过以增量方式，在序列中的每个任务上，通过序列的每个任务来消除此限制，而无需重新访问先前的任务。 Comps持续重复两个子程序：使用RL学习新任务，并使用RL的经验完全离线Meta学习，为后续任务学习做好准备。我们发现，在若干挑战性连续控制任务的旧序列上，Comps优于持续的持续学习和非政策元增强方法。

The reinforcement learning paradigm is a popular way to address problems that have only limited environmental feedback, rather than correctly labeled examples, as is common in other machine learning contexts. While significant progress has been made to improve learning in a single task, the idea of transfer learning has only recently been applied to reinforcement learning tasks. The core idea of transfer is that experience gained in learning to perform one task can help improve learning performance in a related, but different, task. In this article we present a framework that classifies transfer learning methods in terms of their capabilities and goals, and then use it to survey the existing literature, as well as to suggest future directions for transfer learning work.

长期的Horizo​​n机器人学习任务稀疏的奖励对当前的强化学习算法构成了重大挑战。使人类能够学习挑战的控制任务的关键功能是，他们经常获得专家干预，使他们能够在掌握低级控制动作之前了解任务的高级结构。我们为利用专家干预来解决长马增强学习任务的框架。我们考虑\ emph {选项模板}，这是编码可以使用强化学习训练的潜在选项的规格。我们将专家干预提出，因为允许代理商在学习实施之前执行选项模板。这使他们能够使用选项，然后才能为学习成本昂贵的资源学习。我们在三个具有挑战性的强化学习问题上评估了我们的方法，这表明它的表现要优于最先进的方法。训练有素的代理商和我们的代码视频可以在以下网址找到：https：//sites.google.com/view/stickymittens

在本文中，我们提出了一种新的马尔可夫决策过程学习分层表示的方法。我们的方法通过将状态空间划分为子集，并定义用于在分区之间执行转换的子任务。我们制定将状态空间作为优化问题分区的问题，该优化问题可以使用梯度下降给出一组采样的轨迹来解决，使我们的方法适用于大状态空间的高维问题。我们经验验证方法，通过表示它可以成功地在导航域中成功学习有用的分层表示。一旦了解到，分层表示可以用于解决给定域中的不同任务，从而概括跨任务的知识。

使用强化学习解决复杂的问题必须将问题分解为可管理的任务，无论是明确或隐式的任务，并学习解决这些任务的政策。反过来，这些政策必须由采取高级决策的总体政策来控制。这需要培训算法在学习这些政策时考虑这种等级决策结构。但是，实践中的培训可能会导致泛化不良，要么在很少的时间步骤执行动作，要么将其全部转变为单个政策。在我们的工作中，我们介绍了一种替代方法来依次学习此类技能，而无需使用总体层次的政策。我们在环境的背景下提出了这种方法，在这种环境的背景下，学习代理目标的主要组成部分是尽可能长时间延长情节。我们将我们提出的方法称为顺序选择评论家。我们在我们开发的灵活的模拟3D导航环境中演示了我们在导航和基于目标任务的方法的实用性。我们还表明，我们的方法优于先前的方法，例如在我们的环境中，柔软的演员和软选择评论家，以及健身房自动驾驶汽车模拟器和Atari River RAID RAID环境。

A long-standing challenge in artificial intelligence is lifelong learning. In lifelong learning, many tasks are presented in sequence and learners must efficiently transfer knowledge between tasks while avoiding catastrophic forgetting over long lifetimes. On these problems, policy reuse and other multi-policy reinforcement learning techniques can learn many tasks. However, they can generate many temporary or permanent policies, resulting in memory issues. Consequently, there is a need for lifetime-scalable methods that continually refine a policy library of a pre-defined size. This paper presents a first approach to lifetime-scalable policy reuse. To pre-select the number of policies, a notion of task capacity, the maximal number of tasks that a policy can accurately solve, is proposed. To evaluate lifetime policy reuse using this method, two state-of-the-art single-actor base-learners are compared: 1) a value-based reinforcement learner, Deep Q-Network (DQN) or Deep Recurrent Q-Network (DRQN); and 2) an actor-critic reinforcement learner, Proximal Policy Optimisation (PPO) with or without Long Short-Term Memory layer. By selecting the number of policies based on task capacity, D(R)QN achieves near-optimal performance with 6 policies in a 27-task MDP domain and 9 policies in an 18-task POMDP domain; with fewer policies, catastrophic forgetting and negative transfer are observed. Due to slow, monotonic improvement, PPO requires fewer policies, 1 policy for the 27-task domain and 4 policies for the 18-task domain, but it learns the tasks with lower accuracy than D(R)QN. These findings validate lifetime-scalable policy reuse and suggest using D(R)QN for larger and PPO for smaller library sizes.

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.

Deep reinforcement learning algorithms require large amounts of experience to learn an individual task. While in principle meta-reinforcement learning (meta-RL) algorithms enable agents to learn new skills from small amounts of experience, several major challenges preclude their practicality. Current methods rely heavily on on-policy experience, limiting their sample efficiency. The also lack mechanisms to reason about task uncertainty when adapting to new tasks, limiting their effectiveness in sparse reward problems. In this paper, we address these challenges by developing an offpolicy meta-RL algorithm that disentangles task inference and control. In our approach, we perform online probabilistic filtering of latent task variables to infer how to solve a new task from small amounts of experience. This probabilistic interpretation enables posterior sampling for structured and efficient exploration. We demonstrate how to integrate these task variables with off-policy RL algorithms to achieve both metatraining and adaptation efficiency. Our method outperforms prior algorithms in sample efficiency by 20-100X as well as in asymptotic performance on several meta-RL benchmarks.

The ability to effectively reuse prior knowledge is a key requirement when building general and flexible Reinforcement Learning (RL) agents. Skill reuse is one of the most common approaches, but current methods have considerable limitations.For example, fine-tuning an existing policy frequently fails, as the policy can degrade rapidly early in training. In a similar vein, distillation of expert behavior can lead to poor results when given sub-optimal experts. We compare several common approaches for skill transfer on multiple domains including changes in task and system dynamics. We identify how existing methods can fail and introduce an alternative approach to mitigate these problems. Our approach learns to sequence existing temporally-extended skills for exploration but learns the final policy directly from the raw experience. This conceptual split enables rapid adaptation and thus efficient data collection but without constraining the final solution.It significantly outperforms many classical methods across a suite of evaluation tasks and we use a broad set of ablations to highlight the importance of differentc omponents of our method.

For an autonomous agent to fulfill a wide range of user-specified goals at test time, it must be able to learn broadly applicable and general-purpose skill repertoires. Furthermore, to provide the requisite level of generality, these skills must handle raw sensory input such as images. In this paper, we propose an algorithm that acquires such general-purpose skills by combining unsupervised representation learning and reinforcement learning of goal-conditioned policies. Since the particular goals that might be required at test-time are not known in advance, the agent performs a self-supervised "practice" phase where it imagines goals and attempts to achieve them. We learn a visual representation with three distinct purposes: sampling goals for self-supervised practice, providing a structured transformation of raw sensory inputs, and computing a reward signal for goal reaching. We also propose a retroactive goal relabeling scheme to further improve the sample-efficiency of our method. Our off-policy algorithm is efficient enough to learn policies that operate on raw image observations and goals for a real-world robotic system, and substantially outperforms prior techniques. * Equal contribution. Order was determined by coin flip.

强化学习（RL）算法有望为机器人系统实现自主技能获取。但是，实际上，现实世界中的机器人RL通常需要耗时的数据收集和频繁的人类干预来重置环境。此外，当部署超出知识的设置超出其学习的设置时，使用RL学到的机器人政策通常会失败。在这项工作中，我们研究了如何通过从先前看到的任务中收集的各种离线数据集的有效利用来应对这些挑战。当面对一项新任务时，我们的系统会适应以前学习的技能，以快速学习执行新任务并将环境返回到初始状态，从而有效地执行自己的环境重置。我们的经验结果表明，将先前的数据纳入机器人增强学习中可以实现自主学习，从而大大提高了学习的样本效率，并可以更好地概括。

人类通常通过将它们分解为更容易的子问题，然后结合子问题解决方案来解决复杂的问题。这种类型的组成推理允许在解决共享一部分基础构图结构的未来任务时重复使用子问题解决方案。在持续或终身的强化学习（RL）设置中，将知识分解为可重复使用的组件的能力将使代理通过利用积累的组成结构来快速学习新的RL任务。我们基于神经模块探索一种特定形式的组成形式，并提出了一组RL问题，可以直观地接受组成溶液。从经验上讲，我们证明了神经组成确实捕获了问题空间的基本结构。我们进一步提出了一种构图终身RL方法，该方法利用累积的神经成分来加速学习未来任务的学习，同时通过离线RL通过离线RL保留以前的RL，而不是重播经验。

强化学习的关键挑战是解决了长地平规划问题。最近的工作已经利用计划在这些设置中引导钢筋学习。但是，这些方法对用户施加了高手动负担，因为它们必须为每项新任务提供指导计划。部分观察到的环境进一步使编程任务复杂化，因为程序必须实现正确，理想地最佳地实现策略，处理环境的隐藏区域的所有可能配置。我们提出了一种新的方法，模型预测程序合成（MPP），它使用程序综合来自动生成指导程序。它培训了一种生成模型来预测世界的未观察到的部分，然后以鲁棒到其不确定性的方式基于来自该模型的样本来综合程序。在我们的实验中，我们表明我们的方法在一组具有挑战性的基准上显着优于非程序引导的方法，包括2D Minecraft-Inspired环境，代理商必须完成复杂的子组织序列来实现其目标，并实现类似的使用手动程序指导代理的性能。我们的结果表明，我们的方法可以在不需要用户为每项新任务提供新的指导计划的情况下获得方案引导的强化学习的好处。

钢筋学习中的时间抽象（RL），通过更有效地随时间传播信息，提供了提高复杂环境中的泛化和知识传输的承诺。虽然选项学习最初是以允许同时更新许多选项的方式制定的，但使用违规策略，期间内部学习（Sutton，Precup＆Singh，1999），许多最近的分层强化学习方法仅更新一个选项时间：当前正在执行的选项。我们在深度加强学习的背景下重新审视并扩展了内部期间学习，以便启用与当前原始操作选项一致的所有选项，而不会引入任何其他估计。因此，我们的方法可以在大多数分层RL框架中自然采用。当我们将我们的方法与选项发现的选项批评算法结合起来时，我们在各种域中获得了性能和数据效率的显着改进。

元强化学习（RL）方法可以使用比标准RL少的数据级的元培训策略，但元培训本身既昂贵又耗时。如果我们可以在离线数据上进行元训练，那么我们可以重复使用相同的静态数据集，该数据集将一次标记为不同任务的奖励，以在元测试时间适应各种新任务的元训练策略。尽管此功能将使Meta-RL成为现实使用的实用工具，但离线META-RL提出了除在线META-RL或标准离线RL设置之外的其他挑战。 Meta-RL学习了一种探索策略，该策略收集了用于适应的数据，并元培训策略迅速适应了新任务的数据。由于该策略是在固定的离线数据集上进行了元训练的，因此当适应学识渊博的勘探策略收集的数据时，它可能表现得不可预测，这与离线数据有系统地不同，从而导致分布变化。我们提出了一种混合脱机元元素算法，该算法使用带有奖励的脱机数据来进行自适应策略，然后收集其他无监督的在线数据，而无需任何奖励标签来桥接这一分配变化。通过不需要在线收集的奖励标签，此数据可以便宜得多。我们将我们的方法比较了在模拟机器人的运动和操纵任务上进行离线元rl的先前工作，并发现使用其他无监督的在线数据收集可以显着提高元训练政策的自适应能力，从而匹配完全在线的表现。在一系列具有挑战性的域上，需要对新任务进行概括。