生成流动网络（GFLOWNETS）是一种算法家族，用于训练在非均衡目标密度下离散对象的顺序采样器，并已成功用于各种概率建模任务。现有的Gflownets培训目标是国家本地的，或者是过渡的本地，或者在整个采样轨迹上传播奖励信号。我们认为，这些替代方案代表了梯度偏见变化权衡的相反目的，并提出了一种利用这种权衡以减轻其有害影响的方法。受到强化学习的TD（$ \ lambda $）算法的启发，我们介绍了一个subtrajectory Balance或subtb（$ \ lambda $），这是一个GFLOWNET培训目标，可以从不同长度的部分动作子序列中学习。我们表明，SubTB（$ \ lambda $）会在先前研究和新环境中加速采样器的收敛，并在具有更长的动作序列和比以前的可能性更长的环境中培训Gflownets。我们还对随机梯度动力学进行了比较分析，阐明了GFLOWNET训练中的偏差变化权衡以及亚条件平衡的优势。
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已经引入了生成流量网络（GFlowNETS）作为在主动学习背景下采样多样化候选的方法，具有培训目标，其使它们与给定奖励功能成比例地进行比例。在本文中，我们显示了许多额外的GFLOWN的理论特性。它们可用于估计联合概率分布和一些变量未指定的相应边际分布，并且特别感兴趣地，可以代表像集合和图形的复合对象的分布。 Gflownets摊销了通常通过计算昂贵的MCMC方法在单个但训练有素的生成通行证中进行的工作。它们还可用于估计分区功能和自由能量，给定子集（子图）的超标（超图）的条件概率，以及给定集合（图）的所有超标仪（超图）的边际分布。我们引入了熵和相互信息估计的变体，从帕累托前沿采样，与奖励最大化策略的连接，以及随机环境的扩展，连续动作和模块化能量功能。
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本文是关于从一系列动作中学习用于生成对象（如分子图）的随机策略的问题，使得生成对象的概率与该对象的给定的正奖励成比例。虽然标准返回最大化往往会收敛到单个返回最大化序列，但是有些情况我们希望在其中进行不同的高回报解决方案。例如，在可能的情况下，在黑盒功能优化中出现，每次都有很大的批次查询，其中批次应该多样化，例如，在新分子的设计中。人们还可以将其视为大致将能量函数转换为生成分布的问题。虽然MCMC方法可以实现这一点，但它们很昂贵，通常只执行本地探索。相反，培训生成政策在培训期间摊销搜索成本，并产生快速生成。使用时间差异学习的见解，基于生成过程作为流量网络的视图，提出Gflownet，使得可以处理不同轨迹可以产生相同的最终状态的棘手的情况，例如，有许多方法是顺序添加原子以产生一些分子图。我们将一组轨迹作为流程铸造并将流动一致性方程转换为学习目标，类似于钟人方程的铸造成时间差异方法。我们证明，拟议目标的任何全球最低限度都会产生一种从所需分布中采样的策略，并展示了Gflownet在一个简单的领域的提高性能和多样性，其中有许多模式到奖励功能以及分子合成任务。
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We examine the role of memorization in deep learning, drawing connections to capacity, generalization, and adversarial robustness. While deep networks are capable of memorizing noise data, our results suggest that they tend to prioritize learning simple patterns first. In our experiments, we expose qualitative differences in gradient-based optimization of deep neural networks (DNNs) on noise vs. real data. We also demonstrate that for appropriately tuned explicit regularization (e.g., dropout) we can degrade DNN training performance on noise datasets without compromising generalization on real data. Our analysis suggests that the notions of effective capacity which are dataset independent are unlikely to explain the generalization performance of deep networks when trained with gradient based methods because training data itself plays an important role in determining the degree of memorization.
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Practitioners use Hidden Markov Models (HMMs) in different problems for about sixty years. Besides, Conditional Random Fields (CRFs) are an alternative to HMMs and appear in the literature as different and somewhat concurrent models. We propose two contributions. First, we show that basic Linear-Chain CRFs (LC-CRFs), considered as different from the HMMs, are in fact equivalent to them in the sense that for each LC-CRF there exists a HMM - that we specify - whom posterior distribution is identical to the given LC-CRF. Second, we show that it is possible to reformulate the generative Bayesian classifiers Maximum Posterior Mode (MPM) and Maximum a Posteriori (MAP) used in HMMs, as discriminative ones. The last point is of importance in many fields, especially in Natural Language Processing (NLP), as it shows that in some situations dropping HMMs in favor of CRFs was not necessary.
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Mixup is a popular data augmentation technique for training deep neural networks where additional samples are generated by linearly interpolating pairs of inputs and their labels. This technique is known to improve the generalization performance in many learning paradigms and applications. In this work, we first analyze Mixup and show that it implicitly regularizes infinitely many directional derivatives of all orders. We then propose a new method to improve Mixup based on the novel insight. To demonstrate the effectiveness of the proposed method, we conduct experiments across various domains such as images, tabular data, speech, and graphs. Our results show that the proposed method improves Mixup across various datasets using a variety of architectures, for instance, exhibiting an improvement over Mixup by 0.8% in ImageNet top-1 accuracy.
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Using a comprehensive sample of 2,585 bankruptcies from 1990 to 2019, we benchmark the performance of various machine learning models in predicting financial distress of publicly traded U.S. firms. We find that gradient boosted trees outperform other models in one-year-ahead forecasts. Variable permutation tests show that excess stock returns, idiosyncratic risk, and relative size are the more important variables for predictions. Textual features derived from corporate filings do not improve performance materially. In a credit competition model that accounts for the asymmetric cost of default misclassification, the survival random forest is able to capture large dollar profits.
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The term ``neuromorphic'' refers to systems that are closely resembling the architecture and/or the dynamics of biological neural networks. Typical examples are novel computer chips designed to mimic the architecture of a biological brain, or sensors that get inspiration from, e.g., the visual or olfactory systems in insects and mammals to acquire information about the environment. This approach is not without ambition as it promises to enable engineered devices able to reproduce the level of performance observed in biological organisms -- the main immediate advantage being the efficient use of scarce resources, which translates into low power requirements. The emphasis on low power and energy efficiency of neuromorphic devices is a perfect match for space applications. Spacecraft -- especially miniaturized ones -- have strict energy constraints as they need to operate in an environment which is scarce with resources and extremely hostile. In this work we present an overview of early attempts made to study a neuromorphic approach in a space context at the European Space Agency's (ESA) Advanced Concepts Team (ACT).
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When searching for policies, reward-sparse environments often lack sufficient information about which behaviors to improve upon or avoid. In such environments, the policy search process is bound to blindly search for reward-yielding transitions and no early reward can bias this search in one direction or another. A way to overcome this is to use intrinsic motivation in order to explore new transitions until a reward is found. In this work, we use a recently proposed definition of intrinsic motivation, Curiosity, in an evolutionary policy search method. We propose Curiosity-ES, an evolutionary strategy adapted to use Curiosity as a fitness metric. We compare Curiosity with Novelty, a commonly used diversity metric, and find that Curiosity can generate higher diversity over full episodes without the need for an explicit diversity criterion and lead to multiple policies which find reward.
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Reduced order modeling methods are often used as a mean to reduce simulation costs in industrial applications. Despite their computational advantages, reduced order models (ROMs) often fail to accurately reproduce complex dynamics encountered in real life applications. To address this challenge, we leverage NeuralODEs to propose a novel ROM correction approach based on a time-continuous memory formulation. Finally, experimental results show that our proposed method provides a high level of accuracy while retaining the low computational costs inherent to reduced models.
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