我们提出了一种新方法,以正式描述统计推断的要求,并检查程序是否适当使用统计方法。具体而言,我们定义了信仰Hoare逻辑(BHL),以形式化和推理通过假设检验获得的统计信念。对于假设检验的Kripke模型,此程序逻辑是合理的,并且相对完成。我们通过示例证明,BHL对于假设检验中的实际问题有用。在我们的框架中,我们阐明了通过假设检验获得统计信念的先前信念的重要性,并讨论了程序逻辑内外统计推断的全部图片。
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Target Propagation (TP) is a biologically more plausible algorithm than the error backpropagation (BP) to train deep networks, and improving practicality of TP is an open issue. TP methods require the feedforward and feedback networks to form layer-wise autoencoders for propagating the target values generated at the output layer. However, this causes certain drawbacks; e.g., careful hyperparameter tuning is required to synchronize the feedforward and feedback training, and frequent updates of the feedback path are usually required than that of the feedforward path. Learning of the feedforward and feedback networks is sufficient to make TP methods capable of training, but is having these layer-wise autoencoders a necessary condition for TP to work? We answer this question by presenting Fixed-Weight Difference Target Propagation (FW-DTP) that keeps the feedback weights constant during training. We confirmed that this simple method, which naturally resolves the abovementioned problems of TP, can still deliver informative target values to hidden layers for a given task; indeed, FW-DTP consistently achieves higher test performance than a baseline, the Difference Target Propagation (DTP), on four classification datasets. We also present a novel propagation architecture that explains the exact form of the feedback function of DTP to analyze FW-DTP.
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Deformable registration of two-dimensional/three-dimensional (2D/3D) images of abdominal organs is a complicated task because the abdominal organs deform significantly and their contours are not detected in two-dimensional X-ray images. We propose a supervised deep learning framework that achieves 2D/3D deformable image registration between 3D volumes and single-viewpoint 2D projected images. The proposed method learns the translation from the target 2D projection images and the initial 3D volume to 3D displacement fields. In experiments, we registered 3D-computed tomography (CT) volumes to digitally reconstructed radiographs generated from abdominal 4D-CT volumes. For validation, we used 4D-CT volumes of 35 cases and confirmed that the 3D-CT volumes reflecting the nonlinear and local respiratory organ displacement were reconstructed. The proposed method demonstrate the compatible performance to the conventional methods with a dice similarity coefficient of 91.6 \% for the liver region and 85.9 \% for the stomach region, while estimating a significantly more accurate CT values.
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Despite the impact of psychiatric disorders on clinical health, early-stage diagnosis remains a challenge. Machine learning studies have shown that classifiers tend to be overly narrow in the diagnosis prediction task. The overlap between conditions leads to high heterogeneity among participants that is not adequately captured by classification models. To address this issue, normative approaches have surged as an alternative method. By using a generative model to learn the distribution of healthy brain data patterns, we can identify the presence of pathologies as deviations or outliers from the distribution learned by the model. In particular, deep generative models showed great results as normative models to identify neurological lesions in the brain. However, unlike most neurological lesions, psychiatric disorders present subtle changes widespread in several brain regions, making these alterations challenging to identify. In this work, we evaluate the performance of transformer-based normative models to detect subtle brain changes expressed in adolescents and young adults. We trained our model on 3D MRI scans of neurotypical individuals (N=1,765). Then, we obtained the likelihood of neurotypical controls and psychiatric patients with early-stage schizophrenia from an independent dataset (N=93) from the Human Connectome Project. Using the predicted likelihood of the scans as a proxy for a normative score, we obtained an AUROC of 0.82 when assessing the difference between controls and individuals with early-stage schizophrenia. Our approach surpassed recent normative methods based on brain age and Gaussian Process, showing the promising use of deep generative models to help in individualised analyses.
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Transparency of Machine Learning models used for decision support in various industries becomes essential for ensuring their ethical use. To that end, feature attribution methods such as SHAP (SHapley Additive exPlanations) are widely used to explain the predictions of black-box machine learning models to customers and developers. However, a parallel trend has been to train machine learning models in collaboration with other data holders without accessing their data. Such models, trained over horizontally or vertically partitioned data, present a challenge for explainable AI because the explaining party may have a biased view of background data or a partial view of the feature space. As a result, explanations obtained from different participants of distributed machine learning might not be consistent with one another, undermining trust in the product. This paper presents an Explainable Data Collaboration Framework based on a model-agnostic additive feature attribution algorithm (KernelSHAP) and Data Collaboration method of privacy-preserving distributed machine learning. In particular, we present three algorithms for different scenarios of explainability in Data Collaboration and verify their consistency with experiments on open-access datasets. Our results demonstrated a significant (by at least a factor of 1.75) decrease in feature attribution discrepancies among the users of distributed machine learning.
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The ability to record high-fidelity videos at high acquisition rates is central to the study of fast moving phenomena. The difficulty of imaging fast moving scenes lies in a trade-off between motion blur and underexposure noise: On the one hand, recordings with long exposure times suffer from motion blur effects caused by movements in the recorded scene. On the other hand, the amount of light reaching camera photosensors decreases with exposure times so that short-exposure recordings suffer from underexposure noise. In this paper, we propose to address this trade-off by treating the problem of high-speed imaging as an underexposed image denoising problem. We combine recent advances on underexposed image denoising using deep learning and adapt these methods to the specificity of the high-speed imaging problem. Leveraging large external datasets with a sensor-specific noise model, our method is able to speedup the acquisition rate of a High-Speed Camera over one order of magnitude while maintaining similar image quality.
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In the field of reinforcement learning, because of the high cost and risk of policy training in the real world, policies are trained in a simulation environment and transferred to the corresponding real-world environment. However, the simulation environment does not perfectly mimic the real-world environment, lead to model misspecification. Multiple studies report significant deterioration of policy performance in a real-world environment. In this study, we focus on scenarios involving a simulation environment with uncertainty parameters and the set of their possible values, called the uncertainty parameter set. The aim is to optimize the worst-case performance on the uncertainty parameter set to guarantee the performance in the corresponding real-world environment. To obtain a policy for the optimization, we propose an off-policy actor-critic approach called the Max-Min Twin Delayed Deep Deterministic Policy Gradient algorithm (M2TD3), which solves a max-min optimization problem using a simultaneous gradient ascent descent approach. Experiments in multi-joint dynamics with contact (MuJoCo) environments show that the proposed method exhibited a worst-case performance superior to several baseline approaches.
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使用三维(3D)图像传感器的智能监视一直在智能城市的背景下引起人们的注意。在智能监控中,实施了3D图像传感器获取的点云数据的对象检测,以检测移动物体(例如车辆和行人)以确保道路上的安全性。但是,由于光检测和范围(LIDAR)单元用作3D图像传感器或3D图像传感器的安装位置,因此点云数据的特征是多元化的。尽管迄今已研究了从点云数据进行对象检测的各种深度学习(DL)模型,但尚无研究考虑如何根据点云数据的功能使用多个DL模型。在这项工作中,我们提出了一个基于功能的模型选择框架,该框架通过使用多种DL方法并利用两种人工技术生成的伪不完整的训练数据来创建各种DL模型:采样和噪声添加。它根据在真实环境中获取的点云数据的功能,为对象检测任务选择最合适的DL模型。为了证明提出的框架的有效性,我们使用从KITTI数据集创建的基准数据集比较了多个DL模型的性能,并比较了通过真实室外实验获得的对象检测的示例结果。根据情况,DL模型之间的检测准确性高达32%,这证实了根据情况选择适当的DL模型的重要性。
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针对目标的对话任务的先前研究缺乏关键观念,该观念在以目标为导向的人工智能代理的背景下进行了深入研究。在这项研究中,我们提出了目标引导的开放域对话计划(TGCP)任务的任务,以评估神经对话代理是否具有目标对话计划的能力。使用TGCP任务,我们研究了现有检索模型和最新强生成模型的对话计划能力。实验结果揭示了当前技术面临的挑战。
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我们将知识驱动的程序合成(KDP)作为程序综合任务的变体进行了介绍,该任务需要代理来解决一系列程序合成问题。在KDP中,代理应使用早期问题中的知识来解决后期问题。我们提出了一种基于PushGP的新方法来解决KDPS问题,该问题将子程序作为知识。所提出的方法通过偶数分区(EP)方法从先前解决的问题的解中提取子程序,并使用这些子程序使用自适应替换突变(ARM)来解决即将到来的编程任务。我们称此方法PushGP+EP+ARM。使用PushGP+EP+ARM,在知识提取和利用过程中不需要人类的努力。我们将提出的方法与PushGP进行比较,以及使用人手动提取的子程序的方法。与PushGP相比,我们的PushGP+EP+ARM可以实现更好的火车错误,成功计数和更快的收敛速度。此外,当连续解决六个程序合成问题的序列时,我们证明了PushGP+EP+组的优势。
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