Contrastive learning methods based on InfoNCE loss are popular in node representation learning tasks on graph-structured data. However, its reliance on data augmentation and its quadratic computational complexity might lead to inconsistency and inefficiency problems. To mitigate these limitations, in this paper, we introduce a simple yet effective contrastive model named Localized Graph Contrastive Learning (Local-GCL in short). Local-GCL consists of two key designs: 1) We fabricate the positive examples for each node directly using its first-order neighbors, which frees our method from the reliance on carefully-designed graph augmentations; 2) To improve the efficiency of contrastive learning on graphs, we devise a kernelized contrastive loss, which could be approximately computed in linear time and space complexity with respect to the graph size. We provide theoretical analysis to justify the effectiveness and rationality of the proposed methods. Experiments on various datasets with different scales and properties demonstrate that in spite of its simplicity, Local-GCL achieves quite competitive performance in self-supervised node representation learning tasks on graphs with various scales and properties.

Growing materials data and data-driven informatics drastically promote the discovery and design of materials. While there are significant advancements in data-driven models, the quality of data resources is less studied despite its huge impact on model performance. In this work, we focus on data bias arising from uneven coverage of materials families in existing knowledge. Observing different diversities among crystal systems in common materials databases, we propose an information entropy-based metric for measuring this bias. To mitigate the bias, we develop an entropy-targeted active learning (ET-AL) framework, which guides the acquisition of new data to improve the diversity of underrepresented crystal systems. We demonstrate the capability of ET-AL for bias mitigation and the resulting improvement in downstream machine learning models. This approach is broadly applicable to data-driven materials discovery, including autonomous data acquisition and dataset trimming to reduce bias, as well as data-driven informatics in other scientific domains.

Aiming at exploiting the rich information in user behaviour sequences, sequential recommendation has been widely adopted in real-world recommender systems. However, current methods suffer from the following issues: 1) sparsity of user-item interactions, 2) uncertainty of sequential records, 3) long-tail items. In this paper, we propose to incorporate contrastive learning into the framework of Variational AutoEncoders to address these challenges simultaneously. Firstly, we introduce ContrastELBO, a novel training objective that extends the conventional single-view ELBO to two-view case and theoretically builds a connection between VAE and contrastive learning from a two-view perspective. Then we propose Contrastive Variational AutoEncoder (ContrastVAE in short), a two-branched VAE model with contrastive regularization as an embodiment of ContrastELBO for sequential recommendation. We further introduce two simple yet effective augmentation strategies named model augmentation and variational augmentation to create a second view of a sequence and thus making contrastive learning possible. Experiments on four benchmark datasets demonstrate the effectiveness of ContrastVAE and the proposed augmentation methods. Codes are available at https://github.com/YuWang-1024/ContrastVAE

数据驱动的设计显示了加速材料发现的希望，但由于搜索化学，结构和合成方法的庞大设计空间的高昂成本，这是具有挑战性的。贝叶斯优化（BO）采用不确定性的机器学习模型来选择有前途的设计来评估，从而降低成本。但是，在材料设计中特别感兴趣的具有混合数值和分类变量的BO尚未得到很好的研究。在这项工作中，我们调查了使用混合变量对机器学习的不确定性量化的常见主义者和贝叶斯方法。然后，我们使用来自每个组的流行代表模型，基于森林的LOLO模型（频繁主义者）和潜在的可变高斯过程模型（贝叶斯）进行了对BO中其表现的系统比较研究。我们研究了这两个模型在数学函数优化的功效以及结构和功能材料的特性，在其中我们观察到与问题维度和复杂性有关的性能差异。通过研究机器学习模型的预测性和不确定性估计功能，我们可以解释观察到的性能差异。我们的结果为在材料设计中的混合变量BO中选择频繁和贝叶斯不确定性的机器学习模型提供了实用的指导。

In the new era of personalization, learning the heterogeneous treatment effect (HTE) becomes an inevitable trend with numerous applications. Yet, most existing HTE estimation methods focus on independently and identically distributed observations and cannot handle the non-stationarity and temporal dependency in the common panel data setting. The treatment evaluators developed for panel data, on the other hand, typically ignore the individualized information. To fill the gap, in this paper, we initialize the study of HTE estimation in panel data. Under different assumptions for HTE identifiability, we propose the corresponding heterogeneous one-side and two-side synthetic learner, namely H1SL and H2SL, by leveraging the state-of-the-art HTE estimator for non-panel data and generalizing the synthetic control method that allows flexible data generating process. We establish the convergence rates of the proposed estimators. The superior performance of the proposed methods over existing ones is demonstrated by extensive numerical studies.

学习证明（POL）建议模型所有者使用机器学习培训检查站，以建立已经花费了必要的培训计算的证明。 POL FIREGO加密方法和贸易严格的安全性的作者通过适用于随机梯度下降和适应性变体，可扩展到深度学习。缺乏正式分析使攻击者可能能够为他们没有训练的模型提供证据。我们对为什么不能正式（DIS）正式分析POL协议可抵抗欺骗对手。为此，我们在POL中解开了证明验证的两个角色：（a）有效确定证明是否是有效的梯度下降轨迹，以及（b）确定优先级，使在培训完成后制作证明（即。 ，欺骗）。我们表明，有效的验证会导致接受合法证明和拒绝无效的证据之间的权衡，因为深度学习必然涉及噪音。没有针对这种噪声如何影响训练的精确分析模型，我们无法正式保证POL验证算法是否强大。然后，我们证明，建立优先级也可以鲁棒化地减少到学习理论中的一个开放问题：欺骗Pol Pol hoc hoc训练类似于在非凸X学习中找到具有相同终点的不同轨迹。但是，我们不严格地知道对最终模型权重的先验知识是否有助于发现此类轨迹。我们得出的结论是，在解决上述开放问题之前，可能需要更严重地依靠密码学来制定新的POL协议，并提供正式的鲁棒性保证。特别是，这将有助于建立优先级。作为我们分析的见解的副产品，我们还展示了对POL的两次新攻击。

封闭曲线的建模和不确定性量化是形状分析领域的重要问题，并且可以对随后的统计任务产生重大影响。这些任务中的许多涉及封闭曲线的集合，这些曲线通常在多个层面上表现出结构相似性。以有效融合这种曲线间依赖性的方式对多个封闭曲线进行建模仍然是一个具有挑战性的问题。在这项工作中，我们提出并研究了一个多数输出（又称多输出），多维高斯流程建模框架。我们说明了提出的方法学进步，并在几个曲线和形状相关的任务上证明了有意义的不确定性量化的实用性。这种基于模型的方法不仅解决了用内核构造对封闭曲线（及其形状）的推断问题，而且还为通常对功能对象的多层依赖性的非参数建模打开了门。

个性化决定规则（IDR）是一个决定函数，可根据他/她观察到的特征分配给定的治疗。文献中的大多数现有工作考虑使用二进制或有限的许多治疗方案的设置。在本文中，我们专注于连续治疗设定，并提出跳跃间隔 - 学习，开发一个最大化预期结果的个性化间隔值决定规则（I2DR）。与推荐单一治疗的IDRS不同，所提出的I2DR为每个人产生了一系列治疗方案，使其在实践中实施更加灵活。为了获得最佳I2DR，我们的跳跃间隔学习方法估计通过跳转惩罚回归给予治疗和协变量的结果的条件平均值，并基于估计的结果回归函数来衍生相应的最佳I2DR。允许回归线是用于清晰的解释或深神经网络的线性，以模拟复杂的处理 - 协调会相互作用。为了实现跳跃间隔学习，我们开发了一种基于动态编程的搜索算法，其有效计算结果回归函数。当结果回归函数是处理空间的分段或连续功能时，建立所得I2DR的统计特性。我们进一步制定了一个程序，以推断（估计）最佳政策下的平均结果。进行广泛的模拟和对华法林研究的真实数据应用，以证明所提出的I2DR的经验有效性。

Evaluating the performance of an ongoing policy plays a vital role in many areas such as medicine and economics, to provide crucial instruction on the early-stop of the online experiment and timely feedback from the environment. Policy evaluation in online learning thus attracts increasing attention by inferring the mean outcome of the optimal policy (i.e., the value) in real-time. Yet, such a problem is particularly challenging due to the dependent data generated in the online environment, the unknown optimal policy, and the complex exploration and exploitation trade-off in the adaptive experiment. In this paper, we aim to overcome these difficulties in policy evaluation for online learning. We explicitly derive the probability of exploration that quantifies the probability of exploring the non-optimal actions under commonly used bandit algorithms. We use this probability to conduct valid inference on the online conditional mean estimator under each action and develop the doubly robust interval estimation (DREAM) method to infer the value under the estimated optimal policy in online learning. The proposed value estimator provides double protection on the consistency and is asymptotically normal with a Wald-type confidence interval provided. Extensive simulations and real data applications are conducted to demonstrate the empirical validity of the proposed DREAM method.

个性化医学是针对患者特征量身定制的医学范式，是医疗保健中越来越有吸引力的领域。个性化医学的一个重要目标是根据基线协变量鉴定患者的亚组，而与其他比较治疗相比，从目标治疗中受益更多。当前的大多数亚组识别方法仅着重于获得具有增强治疗效果的亚组，而无需注意亚组大小。但是，临床上有意义的亚组学习方法应确定可以从更好的治疗中受益的患者数量的最大数量。在本文中，我们提出了一项最佳的亚组选择规则（SSR），该规则最大化选定的患者的数量，同时，达到了预先指定的临床意义上有意义的平均结果，例如平均治疗效果。我们基于描述结果中的处理 - 果膜相互作用的对比函数，得出了最佳SSR的两种等效理论形式。我们进一步提出了一个受约束的策略树搜索算法（资本），以在可解释的决策树类中找到最佳SSR。所提出的方法是灵活的，可以处理多种限制因素，以惩罚具有负面治疗效果的患者，并使用受限的平均生存时间作为临床上有趣的平均结果来解决事件数据的时间。进行了广泛的模拟，比较研究和实际数据应用，以证明我们方法的有效性和实用性。