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.

在强化学习中，就其诱导的最佳政策而言，不同的奖励功能可以等效。一个特别众所周知的重要例子是潜在的塑造，可以将一类函数添加到任何奖励功能中，而无需更改任意过渡动态下设置的最佳策略。潜在的塑形在概念上类似于数学和物理学中的潜在，保守的矢量场和规范变换，但是以前尚未正式探索这种联系。我们在图表上开发了一种形式主义，用于抽象马尔可夫决策过程的图表，并显示如何将潜在塑造正式解释为本框架中的梯度。这使我们能够加强Ng等人的结果。 （1999）描述了潜在塑造是始终保留最佳政策的唯一添加奖励转换的条件。作为我们形式主义的附加应用，我们定义了从每个潜在塑造等效类中挑选单个唯一奖励功能的规则。

关于组合优化的机器学习的最新作品表明，基于学习的方法可以优于速度和性能方面的启发式方法。在本文中，我们考虑了在定向的无环图上找到最佳拓扑顺序的问题，重点是编译器中出现的记忆最小化问题。我们提出了一种基于端到端的机器学习方法，用于使用编码器框架，用于拓扑排序。我们的编码器是一种基于注意力的新图形神经网络体系结构，称为\ emph {topoformer}，它使用DAG的不同拓扑转换来传递消息。由编码器产生的节点嵌入被转换为节点优先级，解码器使用这些嵌入，以生成概率分布对拓扑顺序。我们在称为分层图的合成生成图的数据集上训练我们的模型。我们表明，我们的模型的表现优于或在PAR上，具有多个拓扑排序基线，同时在最多2K节点的合成图上明显更快。我们还在一组现实世界计算图上训练和测试我们的模型，显示了性能的改进。

通过加强学习（RL）解决机器人导航任务是由于其稀疏奖励和长决策范围自然而挑战。但是，在许多导航任务中，可以使用高级（HL）任务表示，如粗略楼层。以前的工作通过HL表示中的路径规划组成的层次方法和使用从计划导出的子目标来指导源任务中的RL策略的子目标来证明了高效的学习。然而，这些方法通常忽略计划期间机器人的复杂动态和子最优的子目标达到能力。通过提出利用用于HL代表的培训计划政策的新型分层框架，这项工作克服了这些限制。因此，可以利用收集的卷展数据来学习机器人能力和环境条件。我们专门以学习的转换模型（VI-RL）为基础介绍一个规划策略。在模拟机器人导航任务中，VI-RL对Vanilla RL的一致强烈改善，与单个布局的单个布局有关，但更广泛适用于多个布局，并且与停车处的可训练HL路径规划基准相提并论具有困难的非完全动态的任务，其中它显示了显着的改进。

路由问题是许多实际应用的一类组合问题。最近，已经提出了端到端的深度学习方法，以了解这些问题的近似解决方案启发式。相比之下，经典动态编程（DP）算法保证最佳解决方案，但与问题大小严重规模。我们提出了深入的政策动态规划（DPDP），旨在将学习神经启发式的优势与DP算法结合起来。 DPDP优先确定并限制DP状态空间，使用来自深度神经网络的策略进行培训，以预测示例解决方案的边缘。我们在旅行推销员问题（TSP）上评估我们的框架，车辆路由问题（VRP）和TSP与时间窗口（TSPTW），并表明神经政策提高了（限制性）DP算法的性能，使其对强有力的替代品具有竞争力如LKH，同时也优于求解TSP，VRP和TSPTWS的大多数其他“神经方法”，其中包含100个节点。

In value-based reinforcement learning methods such as deep Q-learning, function approximation errors are known to lead to overestimated value estimates and suboptimal policies. We show that this problem persists in an actor-critic setting and propose novel mechanisms to minimize its effects on both the actor and the critic. Our algorithm builds on Double Q-learning, by taking the minimum value between a pair of critics to limit overestimation. We draw the connection between target networks and overestimation bias, and suggest delaying policy updates to reduce per-update error and further improve performance. We evaluate our method on the suite of OpenAI gym tasks, outperforming the state of the art in every environment tested.

Modeling lies at the core of both the financial and the insurance industry for a wide variety of tasks. The rise and development of machine learning and deep learning models have created many opportunities to improve our modeling toolbox. Breakthroughs in these fields often come with the requirement of large amounts of data. Such large datasets are often not publicly available in finance and insurance, mainly due to privacy and ethics concerns. This lack of data is currently one of the main hurdles in developing better models. One possible option to alleviating this issue is generative modeling. Generative models are capable of simulating fake but realistic-looking data, also referred to as synthetic data, that can be shared more freely. Generative Adversarial Networks (GANs) is such a model that increases our capacity to fit very high-dimensional distributions of data. While research on GANs is an active topic in fields like computer vision, they have found limited adoption within the human sciences, like economics and insurance. Reason for this is that in these fields, most questions are inherently about identification of causal effects, while to this day neural networks, which are at the center of the GAN framework, focus mostly on high-dimensional correlations. In this paper we study the causal preservation capabilities of GANs and whether the produced synthetic data can reliably be used to answer causal questions. This is done by performing causal analyses on the synthetic data, produced by a GAN, with increasingly more lenient assumptions. We consider the cross-sectional case, the time series case and the case with a complete structural model. It is shown that in the simple cross-sectional scenario where correlation equals causation the GAN preserves causality, but that challenges arise for more advanced analyses.

We present the interpretable meta neural ordinary differential equation (iMODE) method to rapidly learn generalizable (i.e., not parameter-specific) dynamics from trajectories of multiple dynamical systems that vary in their physical parameters. The iMODE method learns meta-knowledge, the functional variations of the force field of dynamical system instances without knowing the physical parameters, by adopting a bi-level optimization framework: an outer level capturing the common force field form among studied dynamical system instances and an inner level adapting to individual system instances. A priori physical knowledge can be conveniently embedded in the neural network architecture as inductive bias, such as conservative force field and Euclidean symmetry. With the learned meta-knowledge, iMODE can model an unseen system within seconds, and inversely reveal knowledge on the physical parameters of a system, or as a Neural Gauge to "measure" the physical parameters of an unseen system with observed trajectories. We test the validity of the iMODE method on bistable, double pendulum, Van der Pol, Slinky, and reaction-diffusion systems.

We propose Hierarchical ProtoPNet: an interpretable network that explains its reasoning process by considering the hierarchical relationship between classes. Different from previous methods that explain their reasoning process by dissecting the input image and finding the prototypical parts responsible for the classification, we propose to explain the reasoning process for video action classification by dissecting the input video frames on multiple levels of the class hierarchy. The explanations leverage the hierarchy to deal with uncertainty, akin to human reasoning: When we observe water and human activity, but no definitive action it can be recognized as the water sports parent class. Only after observing a person swimming can we definitively refine it to the swimming action. Experiments on ActivityNet and UCF-101 show performance improvements while providing multi-level explanations.

Artificial intelligence (AI) in the form of deep learning bears promise for drug discovery and chemical biology, $\textit{e.g.}$, to predict protein structure and molecular bioactivity, plan organic synthesis, and design molecules $\textit{de novo}$. While most of the deep learning efforts in drug discovery have focused on ligand-based approaches, structure-based drug discovery has the potential to tackle unsolved challenges, such as affinity prediction for unexplored protein targets, binding-mechanism elucidation, and the rationalization of related chemical kinetic properties. Advances in deep learning methodologies and the availability of accurate predictions for protein tertiary structure advocate for a $\textit{renaissance}$ in structure-based approaches for drug discovery guided by AI. This review summarizes the most prominent algorithmic concepts in structure-based deep learning for drug discovery, and forecasts opportunities, applications, and challenges ahead.