必须校准不确定性估计值(即准确)和清晰(即信息性),以便有用。这激发了各种重新校准的方法,这些方法使用固定数据将未校准的模型转化为校准模型。但是,由于原始模型也是概率模型,因此现有方法的适用性受到限制。我们在回归中引入了一种用于重新校准的算法类别,我们称为模块化保形校准(MCC)。该框架允许人们将任何回归模型转换为校准的概率模型。 MCC的模块化设计使我们能够对现有算法进行简单调整,以实现良好的分配预测。我们还为MCC算法提供有限样本的校准保证。我们的框架恢复了等渗的重新校准,保形校准和共形间隔预测,这意味着我们的理论结果也适用于这些方法。最后,我们对17个回归数据集进行了MCC的经验研究。我们的结果表明,在我们的框架中设计的新算法实现了接近完美的校准,并相对于现有方法提高了清晰度。
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作为算法公平性的概念,多核算已被证明是一个强大而多才多艺的概念,其含义远远超出了其最初的意图。这个严格的概念 - 预测在丰富的相交子群中得到了很好的校准 - 以成本为代价提供了强大的保证:学习成型预测指标的计算和样本复杂性很高,并且随着类标签的数量而成倍增长。相比之下,可以更有效地实现多辅助性的放松概念,但是,仅假设单独使用多学历,就无法保证许多最可取的多核能概念。这种紧张局势提出了一个关键问题:我们能否以多核式式保证来学习预测因素,以与多审核级相称?在这项工作中,我们定义并启动了低度多核的研究。低度的多核净化定义了越来越强大的多组公平性概念的层次结构,这些概念跨越了多辅助性和极端的多核电的原始表述。我们的主要技术贡献表明,与公平性和准确性有关的多核算的关键特性实际上表现为低级性质。重要的是,我们表明,低度的数学振动可以比完整的多核电更有效。在多级设置中,实现低度多核的样品复杂性在完整的多核电上呈指数级(在类中)提高。我们的工作提供了令人信服的证据,表明低度多核能代表了一个最佳位置,将计算和样品效率配对,并提供了强大的公平性和准确性保证。
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通过从完全标记的源域中利用数据,无监督域适应(UDA)通过显式差异最小化数据分布或对抗学习来提高未标记的目标域上的分类性能。作为增强,通过利用模型预测来加强目标特征识别期间涉及类别对齐。但是,在目标域上的错误类别预测中产生的伪标签不准确以及由源域的过度录制引起的分发偏差存在未探明的问题。在本文中,我们提出了一种模型 - 不可知的两阶段学习框架,这大大减少了使用软伪标签策略的缺陷模型预测,并避免了课程学习策略的源域上的过度拟合。从理论上讲,它成功降低了目标域上预期误差的上限的综合风险。在第一阶段,我们用分布对齐的UDA方法训练一个模型,以获得具有相当高的置位目标域上的软语义标签。为了避免在源域上的过度拟合,在第二阶段,我们提出了一种课程学习策略,以自适应地控制来自两个域的损失之间的加权,以便训练阶段的焦点从源分布逐渐移位到目标分布,以预测信心提升了目标分布在目标领域。对两个知名基准数据集的广泛实验验证了我们提出框架促进促进顶级UDA算法的性能的普遍效果,并展示其一致的卓越性能。
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当在高风险机器人应用程序中部署机器学习模型时,检测不安全情况的能力至关重要。当迫在眉睫的情况下(在没有纠正措施的情况下),预警系统可以提供警报。为了可靠地提高安全性,这些警告系统应具有可证明的假负率;即,在没有警报的情况下,将发生不安全的情况,少于$ \ epsilon $。在这项工作中,我们提出了一个框架,将一种统计推理技术与机器人/环境动力学的模拟器相结合,以调整警告系统,以实现$ \ epsilon $ false的负率,使用$ 1//$ 1/\ epsilon $数据点。我们将框架应用于驾驶员警告系统和机器人抓握应用程序,并在经验上证明了错误的负率,同时也观察到较低的虚假检测(正)率。
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概率分类器输出置信信心得分随着他们的预测,并且应该校准这些置信分数,即,它们应该反映预测的可靠性。最小化标准度量的置信度分数,例如预期的校准误差(ECE)准确地测量整个人口平均值的可靠性。然而,通常不可能测量单独预测的可靠性。在这项工作中,我们提出了本地校准误差(LCE),以跨越平均值和各个可靠性之间的间隙。对于每个单独的预测,LCE测量一组类似预测的平均可靠性,其中通过预先训练的特征空间上的内核函数和通过预测模型信仰的融合方案来量化相似性。我们从理论上显示了LCE可以从数据估计,并经验地发现它显示出比ECE可以检测到更细粒度的错误级别模式。我们的关键结果是一种新颖的局部重新校准方法,以改善个人预测的置信度分数并减少LCE。实验,我们表明我们的重新校准方法产生更准确的置信度分数,从而提高了具有图像和表格数据的分类任务的下游公平性和决策。
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Benefiting from the intrinsic supervision information exploitation capability, contrastive learning has achieved promising performance in the field of deep graph clustering recently. However, we observe that two drawbacks of the positive and negative sample construction mechanisms limit the performance of existing algorithms from further improvement. 1) The quality of positive samples heavily depends on the carefully designed data augmentations, while inappropriate data augmentations would easily lead to the semantic drift and indiscriminative positive samples. 2) The constructed negative samples are not reliable for ignoring important clustering information. To solve these problems, we propose a Cluster-guided Contrastive deep Graph Clustering network (CCGC) by mining the intrinsic supervision information in the high-confidence clustering results. Specifically, instead of conducting complex node or edge perturbation, we construct two views of the graph by designing special Siamese encoders whose weights are not shared between the sibling sub-networks. Then, guided by the high-confidence clustering information, we carefully select and construct the positive samples from the same high-confidence cluster in two views. Moreover, to construct semantic meaningful negative sample pairs, we regard the centers of different high-confidence clusters as negative samples, thus improving the discriminative capability and reliability of the constructed sample pairs. Lastly, we design an objective function to pull close the samples from the same cluster while pushing away those from other clusters by maximizing and minimizing the cross-view cosine similarity between positive and negative samples. Extensive experimental results on six datasets demonstrate the effectiveness of CCGC compared with the existing state-of-the-art algorithms.
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As one of the prevalent methods to achieve automation systems, Imitation Learning (IL) presents a promising performance in a wide range of domains. However, despite the considerable improvement in policy performance, the corresponding research on the explainability of IL models is still limited. Inspired by the recent approaches in explainable artificial intelligence methods, we proposed a model-agnostic explaining framework for IL models called R2RISE. R2RISE aims to explain the overall policy performance with respect to the frames in demonstrations. It iteratively retrains the black-box IL model from the randomized masked demonstrations and uses the conventional evaluation outcome environment returns as the coefficient to build an importance map. We also conducted experiments to investigate three major questions concerning frames' importance equality, the effectiveness of the importance map, and connections between importance maps from different IL models. The result shows that R2RISE successfully distinguishes important frames from the demonstrations.
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Text clustering and topic extraction are two important tasks in text mining. Usually, these two tasks are performed separately. For topic extraction to facilitate clustering, we can first project texts into a topic space and then perform a clustering algorithm to obtain clusters. To promote topic extraction by clustering, we can first obtain clusters with a clustering algorithm and then extract cluster-specific topics. However, this naive strategy ignores the fact that text clustering and topic extraction are strongly correlated and follow a chicken-and-egg relationship. Performing them separately fails to make them mutually benefit each other to achieve the best overall performance. In this paper, we propose an unsupervised text clustering and topic extraction framework (ClusTop) which integrates text clustering and topic extraction into a unified framework and can achieve high-quality clustering result and extract topics from each cluster simultaneously. Our framework includes four components: enhanced language model training, dimensionality reduction, clustering and topic extraction, where the enhanced language model can be viewed as a bridge between clustering and topic extraction. On one hand, it provides text embeddings with a strong cluster structure which facilitates effective text clustering; on the other hand, it pays high attention on the topic related words for topic extraction because of its self-attention architecture. Moreover, the training of enhanced language model is unsupervised. Experiments on two datasets demonstrate the effectiveness of our framework and provide benchmarks for different model combinations in this framework.
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An increasing number of public datasets have shown a marked clinical impact on assessing anatomical structures. However, each of the datasets is small, partially labeled, and rarely investigates severe tumor subjects. Moreover, current models are limited to segmenting specific organs/tumors, which can not be extended to novel domains and classes. To tackle these limitations, we introduce embedding learned from Contrastive Language-Image Pre-training (CLIP) to segmentation models, dubbed the CLIP-Driven Universal Model. The Universal Model can better segment 25 organs and 6 types of tumors by exploiting the semantic relationship between abdominal structures. The model is developed from an assembly of 14 datasets with 3,410 CT scans and evaluated on 6,162 external CT scans from 3 datasets. We rank first on the public leaderboard of the Medical Segmentation Decathlon (MSD) and achieve the state-of-the-art results on Beyond The Cranial Vault (BTCV). Compared with dataset-specific models, the Universal Model is computationally more efficient (6x faster), generalizes better to CT scans from varying sites, and shows stronger transfer learning performance on novel tasks. The design of CLIP embedding enables the Universal Model to be easily extended to new classes without catastrophically forgetting the previously learned classes.
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Recent advances in self-supervised learning (SSL) in computer vision are primarily comparative, whose goal is to preserve invariant and discriminative semantics in latent representations by comparing siamese image views. However, the preserved high-level semantics do not contain enough local information, which is vital in medical image analysis (e.g., image-based diagnosis and tumor segmentation). To mitigate the locality problem of comparative SSL, we propose to incorporate the task of pixel restoration for explicitly encoding more pixel-level information into high-level semantics. We also address the preservation of scale information, a powerful tool in aiding image understanding but has not drawn much attention in SSL. The resulting framework can be formulated as a multi-task optimization problem on the feature pyramid. Specifically, we conduct multi-scale pixel restoration and siamese feature comparison in the pyramid. In addition, we propose non-skip U-Net to build the feature pyramid and develop sub-crop to replace multi-crop in 3D medical imaging. The proposed unified SSL framework (PCRLv2) surpasses its self-supervised counterparts on various tasks, including brain tumor segmentation (BraTS 2018), chest pathology identification (ChestX-ray, CheXpert), pulmonary nodule detection (LUNA), and abdominal organ segmentation (LiTS), sometimes outperforming them by large margins with limited annotations.
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