基于仿真的推理(SBI)正在迅速将自己确立为一种标准的机器学习技术,用于分析宇宙学调查中的数据。尽管通过学习模型对密度估计的质量持续改进,但这种技术对真实数据的应用完全依赖于远远超出培训分布的神经网络的概括能力,这主要是不受限制的。由于科学家创建的模拟的不完美,以及产生所有可能参数组合的巨大计算费用,因此,宇宙学中的SBI方法很容易受到此类概括性问题的影响。在这里,我们讨论了这两个问题的效果,并展示如何使用贝叶斯神经网络框架进行训练SBI可以减轻偏见,并在培训集外产生更可靠的推理。我们介绍了CosmosWag,这是平均随机重量的首次应用,并将其应用于经过训练的SBI,以推断宇宙微波背景。
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我们提出了一种隐含的可能性方法,可以通过分散目录数据量化宇宙学信息,并作为图形组装。为此,我们使用模拟暗物质光环目录探索宇宙学的推断。我们采用最大化神经网络(IMNN)的信息来量化Fisher信息提取,这是图表的函数。我们a)在无噪声限制下,模块图结构对基础宇宙学具有高度敏感性,b)表明,通过比较传统统计,网络自动结合质量和聚类信息,c)证明图形神经网络仍然可以提取信息。当目录受到嘈杂的调查削减时,d)说明了如何将非线性IMNN摘要用作贝叶斯隐性可能性推断的渐近最佳压缩统计。我们在两点相关功能上,我们将$ \ omega_m,\ sigma_8 $参数约束降低了42倍,并证明网络自动组合质量和聚类信息,将关节$ \ omega_m,\ sigma_8 $参数约束减少42倍。 。这项工作利用了JAX中的图形数据的新IMNN实现,该实现可以利用数值或自动差异性。我们还显示,IMNNS成功地压缩了远离拟合网络的基准模型的模拟,这表明基于目录的分析中$ n $ point统计的有希望的替代方法。
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贝叶斯工作流程通常需要引入滋扰参数,但对于核心科学建模,需要访问边缘后部密度。在这项工作中,我们使用掩盖的自回归流量和内核密度估计器封装边缘后部,使我们能够计算边际kullback-leibler脱离器和边缘贝叶斯模型尺寸,此外还可以生成样品和计算边际对数概率。我们将其应用于暗能量调查的局部宇宙学示例和全局21cm信号实验。除了计算边缘贝叶斯统计数据外,这项工作对于在贝叶斯实验设计,复杂的先验建模和似然仿真中进一步应用也很重要。该技术可在PIP可容纳的代码人造黄油中公开获得。
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Efficient and robust control using spiking neural networks (SNNs) is still an open problem. Whilst behaviour of biological agents is produced through sparse and irregular spiking patterns, which provide both robust and efficient control, the activity patterns in most artificial spiking neural networks used for control are dense and regular -- resulting in potentially less efficient codes. Additionally, for most existing control solutions network training or optimization is necessary, even for fully identified systems, complicating their implementation in on-chip low-power solutions. The neuroscience theory of Spike Coding Networks (SCNs) offers a fully analytical solution for implementing dynamical systems in recurrent spiking neural networks -- while maintaining irregular, sparse, and robust spiking activity -- but it's not clear how to directly apply it to control problems. Here, we extend SCN theory by incorporating closed-form optimal estimation and control. The resulting networks work as a spiking equivalent of a linear-quadratic-Gaussian controller. We demonstrate robust spiking control of simulated spring-mass-damper and cart-pole systems, in the face of several perturbations, including input- and system-noise, system disturbances, and neural silencing. As our approach does not need learning or optimization, it offers opportunities for deploying fast and efficient task-specific on-chip spiking controllers with biologically realistic activity.
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Algorithms that involve both forecasting and optimization are at the core of solutions to many difficult real-world problems, such as in supply chains (inventory optimization), traffic, and in the transition towards carbon-free energy generation in battery/load/production scheduling in sustainable energy systems. Typically, in these scenarios we want to solve an optimization problem that depends on unknown future values, which therefore need to be forecast. As both forecasting and optimization are difficult problems in their own right, relatively few research has been done in this area. This paper presents the findings of the ``IEEE-CIS Technical Challenge on Predict+Optimize for Renewable Energy Scheduling," held in 2021. We present a comparison and evaluation of the seven highest-ranked solutions in the competition, to provide researchers with a benchmark problem and to establish the state of the art for this benchmark, with the aim to foster and facilitate research in this area. The competition used data from the Monash Microgrid, as well as weather data and energy market data. It then focused on two main challenges: forecasting renewable energy production and demand, and obtaining an optimal schedule for the activities (lectures) and on-site batteries that lead to the lowest cost of energy. The most accurate forecasts were obtained by gradient-boosted tree and random forest models, and optimization was mostly performed using mixed integer linear and quadratic programming. The winning method predicted different scenarios and optimized over all scenarios jointly using a sample average approximation method.
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A reduced order model of a generic submarine is presented. Computational fluid dynamics (CFD) results are used to create and validate a model that includes depth dependence and the effect of waves on the craft. The model and the procedure to obtain its coefficients are discussed, and examples of the data used to obtain the model coefficients are presented. An example of operation following a complex path is presented and results from the reduced order model are compared to those from an equivalent CFD calculation. The controller implemented to complete these maneuvers is also presented.
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Neural machine translation (NMT) has become the de-facto standard in real-world machine translation applications. However, NMT models can unpredictably produce severely pathological translations, known as hallucinations, that seriously undermine user trust. It becomes thus crucial to implement effective preventive strategies to guarantee their proper functioning. In this paper, we address the problem of hallucination detection in NMT by following a simple intuition: as hallucinations are detached from the source content, they exhibit encoder-decoder attention patterns that are statistically different from those of good quality translations. We frame this problem with an optimal transport formulation and propose a fully unsupervised, plug-in detector that can be used with any attention-based NMT model. Experimental results show that our detector not only outperforms all previous model-based detectors, but is also competitive with detectors that employ large models trained on millions of samples.
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As more and more conversational and translation systems are deployed in production, it is essential to implement and to develop effective control mechanisms guaranteeing their proper functioning and security. An essential component to ensure safe system behavior is out-of-distribution (OOD) detection, which aims at detecting whether an input sample is statistically far from the training distribution. Although OOD detection is a widely covered topic in classification tasks, it has received much less attention in text generation. This paper addresses the problem of OOD detection for machine translation and dialog generation from an operational perspective. Our contributions include: (i) RAINPROOF a Relative informAItioN Projection ODD detection framework; and (ii) a more operational evaluation setting for OOD detection. Surprisingly, we find that OOD detection is not necessarily aligned with task-specific measures. The OOD detector may filter out samples that are well processed by the model and keep samples that are not, leading to weaker performance. Our results show that RAINPROOF breaks this curse and achieve good results in OOD detection while increasing performance.
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Variance parameter estimation in linear mixed models is a challenge for many classical nonlinear optimization algorithms due to the positive-definiteness constraint of the random effects covariance matrix. We take a completely novel view on parameter estimation in linear mixed models by exploiting the intrinsic geometry of the parameter space. We formulate the problem of residual maximum likelihood estimation as an optimization problem on a Riemannian manifold. Based on the introduced formulation, we give geometric higher-order information on the problem via the Riemannian gradient and the Riemannian Hessian. Based on that, we test our approach with Riemannian optimization algorithms numerically. Our approach yields a higher quality of the variance parameter estimates compared to existing approaches.
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Physics-Informed Neural Networks (PINNs) are gaining popularity as a method for solving differential equations. While being more feasible in some contexts than the classical numerical techniques, PINNs still lack credibility. A remedy for that can be found in Uncertainty Quantification (UQ) which is just beginning to emerge in the context of PINNs. Assessing how well the trained PINN complies with imposed differential equation is the key to tackling uncertainty, yet there is lack of comprehensive methodology for this task. We propose a framework for UQ in Bayesian PINNs (B-PINNs) that incorporates the discrepancy between the B-PINN solution and the unknown true solution. We exploit recent results on error bounds for PINNs on linear dynamical systems and demonstrate the predictive uncertainty on a class of linear ODEs.
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