Information spread on networks can be efficiently modeled by considering three features: documents' content, time of publication relative to other publications, and position of the spreader in the network. Most previous works model up to two of those jointly, or rely on heavily parametric approaches. Building on recent Dirichlet-Point processes literature, we introduce the Houston (Hidden Online User-Topic Network) model, that jointly considers all those features in a non-parametric unsupervised framework. It infers dynamic topic-dependent underlying diffusion networks in a continuous-time setting along with said topics. It is unsupervised; it considers an unlabeled stream of triplets shaped as \textit{(time of publication, information's content, spreading entity)} as input data. Online inference is conducted using a sequential Monte-Carlo algorithm that scales linearly with the size of the dataset. Our approach yields consequent improvements over existing baselines on both cluster recovery and subnetworks inference tasks.

The publication time of a document carries a relevant information about its semantic content. The Dirichlet-Hawkes process has been proposed to jointly model textual information and publication dynamics. This approach has been used with success in several recent works, and extended to tackle specific challenging problems --typically for short texts or entangled publication dynamics. However, the prior in its current form does not allow for complex publication dynamics. In particular, inferred topics are independent from each other --a publication about finance is assumed to have no influence on publications about politics, for instance. In this work, we develop the Multivariate Powered Dirichlet-Hawkes Process (MPDHP), that alleviates this assumption. Publications about various topics can now influence each other. We detail and overcome the technical challenges that arise from considering interacting topics. We conduct a systematic evaluation of MPDHP on a range of synthetic datasets to define its application domain and limitations. Finally, we develop a use case of the MPDHP on Reddit data. At the end of this article, the interested reader will know how and when to use MPDHP, and when not to.

可解释的AI（XAI）是一个重要的发展领域，但仍相对研究用于聚类。我们提出了一种可解释的划分聚类方法，不仅可以找到集群，而且还可以解释每个群集。基于典范的心理学概念学院的使用支持了示例示例的理解。我们表明，找到一小部分示例来解释即使是一个群集也是计算上的棘手。因此，总体问题具有挑战性。我们开发了一种近似算法，该算法可为聚类质量以及所使用的示例数量提供可证明的性能保证。该基本算法解释了每个集群中的所有实例，而另一种近似算法则使用有界数的示例来允许更简单的解释，并证明涵盖了所有实例的大部分。实验结果表明，我们的工作在涉及很难理解图像和文本深层嵌入的领域中很有用。

大多数信息传播模型在线依赖于以下假设：信息彼此独立传播。但是，一些作品指出了研究相互作用在现实世界过程中的作用的必要性，并强调了这样做的可能困难：相互作用稀疏和简短。作为答案，最近的进步开发了模型来说明潜在出版物动态的相互作用。在本文中，我们建议扩展和应用一个这样的模型，以确定Reddit的新闻头条之间的互动是否在其基本出版机制中起重要作用。在对2019年的100,000个新闻标题进行了深入的案例研究之后，我们检索了有关互动的最新结论，并得出结论，它们在该数据集中扮演了较小的角色。

去年，在推荐系统中使用随机块建模（SBM）的兴趣恢复了。这些模型被视为能够处理标记数据的张量分解技术的灵活替代方法。最近提议通过将较大的上下文作为输入数据并在上下文相关元素之间添加二阶交互来解决通过SBM解决离散建议问题的最新作品。在这项工作中，我们表明这些模型都是单个全局框架的特殊情况：序列化的交互混合成员随机块模型（SIMSBM）。它允许建模任意较大的上下文以及任意高级的交互作用。我们证明了SIMSBM概括了一些最近基于SBM的基线。此外，我们证明我们的配方允许在六个现实世界数据集上增加预测能力。

缓慢的新兴主题检测是事件检测之间的任务，我们在短时间内聚合不同单词的行为，以及我们监控他们的长期演进的语言演化。在这项工作中，我们解决了早期检测慢慢新兴的问题的问题。为此，我们收集了单词级别的弱信号的证据。我们建议监视嵌入空间中的单词表示的行为，并使用其几何特性之一来表征主题的出现。随着这种任务通常难以评估，我们提出了一种用于定量评估的框架。我们展示了积极的结果，在新闻和科学文章的两种公共数据集上优于最先进的方法。

In this paper, we address the problem of multimodal emotion recognition from multiple physiological signals. We demonstrate that a Transformer-based approach is suitable for this task. In addition, we present how such models may be pretrained in a multimodal scenario to improve emotion recognition performances. We evaluate the benefits of using multimodal inputs and pre-training with our approach on a state-ofthe-art dataset.

Contrastive representation learning has proven to be an effective self-supervised learning method for images and videos. Most successful approaches are based on Noise Contrastive Estimation (NCE) and use different views of an instance as positives that should be contrasted with other instances, called negatives, that are considered as noise. However, several instances in a dataset are drawn from the same distribution and share underlying semantic information. A good data representation should contain relations between the instances, or semantic similarity and dissimilarity, that contrastive learning harms by considering all negatives as noise. To circumvent this issue, we propose a novel formulation of contrastive learning using semantic similarity between instances called Similarity Contrastive Estimation (SCE). Our training objective is a soft contrastive one that brings the positives closer and estimates a continuous distribution to push or pull negative instances based on their learned similarities. We validate empirically our approach on both image and video representation learning. We show that SCE performs competitively with the state of the art on the ImageNet linear evaluation protocol for fewer pretraining epochs and that it generalizes to several downstream image tasks. We also show that SCE reaches state-of-the-art results for pretraining video representation and that the learned representation can generalize to video downstream tasks.

The number of international benchmarking competitions is steadily increasing in various fields of machine learning (ML) research and practice. So far, however, little is known about the common practice as well as bottlenecks faced by the community in tackling the research questions posed. To shed light on the status quo of algorithm development in the specific field of biomedical imaging analysis, we designed an international survey that was issued to all participants of challenges conducted in conjunction with the IEEE ISBI 2021 and MICCAI 2021 conferences (80 competitions in total). The survey covered participants' expertise and working environments, their chosen strategies, as well as algorithm characteristics. A median of 72% challenge participants took part in the survey. According to our results, knowledge exchange was the primary incentive (70%) for participation, while the reception of prize money played only a minor role (16%). While a median of 80 working hours was spent on method development, a large portion of participants stated that they did not have enough time for method development (32%). 25% perceived the infrastructure to be a bottleneck. Overall, 94% of all solutions were deep learning-based. Of these, 84% were based on standard architectures. 43% of the respondents reported that the data samples (e.g., images) were too large to be processed at once. This was most commonly addressed by patch-based training (69%), downsampling (37%), and solving 3D analysis tasks as a series of 2D tasks. K-fold cross-validation on the training set was performed by only 37% of the participants and only 50% of the participants performed ensembling based on multiple identical models (61%) or heterogeneous models (39%). 48% of the respondents applied postprocessing steps.

Time series is the most prevalent form of input data for educational prediction tasks. The vast majority of research using time series data focuses on hand-crafted features, designed by experts for predictive performance and interpretability. However, extracting these features is labor-intensive for humans and computers. In this paper, we propose an approach that utilizes irregular multivariate time series modeling with graph neural networks to achieve comparable or better accuracy with raw time series clickstreams in comparison to hand-crafted features. Furthermore, we extend concept activation vectors for interpretability in raw time series models. We analyze these advances in the education domain, addressing the task of early student performance prediction for downstream targeted interventions and instructional support. Our experimental analysis on 23 MOOCs with millions of combined interactions over six behavioral dimensions show that models designed with our approach can (i) beat state-of-the-art educational time series baselines with no feature extraction and (ii) provide interpretable insights for personalized interventions. Source code: https://github.com/epfl-ml4ed/ripple/.