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.

由于它们在现实世界中的广泛采用，提高深神经网络（DNN）的运行时性能至关重要。现有的优化DNN的张量代数表达的方法仅考虑由固定的预定义运算符表示的表达式，在一般表达式之间缺少可能的优化机会。我们提出了Ollie，这是第一个基于衍生的张量程序优化器。 Ollie通过利用一般张量代数表达式之间的转换来优化张量程序，从而实现了一个更大的表达搜索空间，其中包括由先前工作作为特殊情况支持的搜索空间。 Ollie使用基于混合衍生的优化器，该优化器有效地结合了探索性和指导性推导，以快速发现高度优化的表达式。对七个DNN的评估表明，Ollie可以在A100 GPU上胜过2.73 $ \ times $（平均为1.46美元$ \ times $），在V100上最多可超过2.68 $ \ times $（1.51 $ \ times $） GPU分别。

双层优化，尤其是基于梯度的类别，已在深度学习社区中广泛使用，包括超参数优化和元知识提取。 BI级优化将一个问题嵌入了另一个问题，基于梯度的类别通过计算超级级别来解决外部级别的任务，这比经典方法（例如进化算法）更有效。在这项调查中，我们首先对基于梯度的双层优化进行正式定义。其次，我们说明了如何将研究问题作为双层优化问题，这对于初学者来说是极大的实际用途。更具体地说，有两种公式：单任务公式，以优化超参数，例如正则化参数和蒸馏数据，以及用于提取元知识的多任务公式，例如模型初始化。然后，使用BI级公式，我们讨论了四个BI级优化求解器，以更新外部变量，包括显式梯度更新，代理更新，隐式函数更新和闭合形式更新。最后但并非最不重要的一点是，我们通过指出基于梯度的双层优化科学问题（AI4Science）的巨大潜力来结束调查。

持续学习（CL）逐步学习一系列任务，其目标是实现两个主要目标：克服灾难性的遗忘（CF）并鼓励跨任务的知识转移（KT）。然而，大多数现有技术只关注克服CF并且没有鼓励KT的机制，因此在KT中不好做得很好。虽然有几篇论文试图处理CF和KT，但我们的实验表明，当任务没有太多的共享知识时，他们患有严重的CF。另一个观察是，大多数电流CL方法不使用预先训练的型号，但已经表明这种模型可以显着提高结束任务性能。例如，在自然语言处理中，微调伯特的预训练语言模型是最有效的方法之一。然而，对于CL，这种方法遭受严重的CF.一个有趣的问题是如何充分利用预先训练的电流模型。本文提出了一种名为CTR的新型模型来解决这些问题。我们的实验结果表明了CTR的有效性

We study the composition style in deep image matting, a notion that characterizes a data generation flow on how to exploit limited foregrounds and random backgrounds to form a training dataset. Prior art executes this flow in a completely random manner by simply going through the foreground pool or by optionally combining two foregrounds before foreground-background composition. In this work, we first show that naive foreground combination can be problematic and therefore derive an alternative formulation to reasonably combine foregrounds. Our second contribution is an observation that matting performance can benefit from a certain occurrence frequency of combined foregrounds and their associated source foregrounds during training. Inspired by this, we introduce a novel composition style that binds the source and combined foregrounds in a definite triplet. In addition, we also find that different orders of foreground combination lead to different foreground patterns, which further inspires a quadruplet-based composition style. Results under controlled experiments on four matting baselines show that our composition styles outperform existing ones and invite consistent performance improvement on both composited and real-world datasets. Code is available at: https://github.com/coconuthust/composition_styles

Script is a kind of structured knowledge extracted from texts, which contains a sequence of events. Based on such knowledge, script event prediction aims to predict the subsequent event. To do so, two aspects should be considered for events, namely, event description (i.e., what the events should contain) and event encoding (i.e., how they should be encoded). Most existing methods describe an event by a verb together with only a few core arguments (i.e., subject, object, and indirect object), which are not precise. In addition, existing event encoders are limited to a fixed number of arguments, which are not flexible to deal with extra information. Thus, in this paper, we propose the Rich Event Prediction (REP) framework for script event prediction. Fundamentally, it is based on the proposed rich event description, which enriches the existing ones with three kinds of important information, namely, the senses of verbs, extra semantic roles, and types of participants. REP contains an event extractor to extract such information from texts. Based on the extracted rich information, a predictor then selects the most probable subsequent event. The core component of the predictor is a transformer-based event encoder to flexibly deal with an arbitrary number of arguments. Experimental results on the widely used Gigaword Corpus show the effectiveness of the proposed framework.

A hallmark of the deep learning era for computer vision is the successful use of large-scale labeled datasets to train feature representations for tasks ranging from object recognition and semantic segmentation to optical flow estimation and novel view synthesis of 3D scenes. In this work, we aim to learn dense discriminative object representations for low-shot category recognition without requiring any category labels. To this end, we propose Deep Object Patch Encodings (DOPE), which can be trained from multiple views of object instances without any category or semantic object part labels. To train DOPE, we assume access to sparse depths, foreground masks and known cameras, to obtain pixel-level correspondences between views of an object, and use this to formulate a self-supervised learning task to learn discriminative object patches. We find that DOPE can directly be used for low-shot classification of novel categories using local-part matching, and is competitive with and outperforms supervised and self-supervised learning baselines. Code and data available at https://github.com/rehg-lab/dope_selfsup.

Continual learning (CL) learns a sequence of tasks incrementally. There are two popular CL settings, class incremental learning (CIL) and task incremental learning (TIL). A major challenge of CL is catastrophic forgetting (CF). While a number of techniques are already available to effectively overcome CF for TIL, CIL remains to be highly challenging. So far, little theoretical study has been done to provide a principled guidance on how to solve the CIL problem. This paper performs such a study. It first shows that probabilistically, the CIL problem can be decomposed into two sub-problems: Within-task Prediction (WP) and Task-id Prediction (TP). It further proves that TP is correlated with out-of-distribution (OOD) detection, which connects CIL and OOD detection. The key conclusion of this study is that regardless of whether WP and TP or OOD detection are defined explicitly or implicitly by a CIL algorithm, good WP and good TP or OOD detection are necessary and sufficient for good CIL performances. Additionally, TIL is simply WP. Based on the theoretical result, new CIL methods are also designed, which outperform strong baselines in both CIL and TIL settings by a large margin.

我们将点隶属关系引入特征Upsmpling，这一概念描述了每个上采样点的隶属关系到具有语义相似性的本地解码器特征点形成的语义群集。通过重新思考点的隶属关系，我们提出了一种通用公式，用于产生上采样内核。内核不仅鼓励语义平滑度，还鼓励上采样的特征图中的边界清晰度。此类属性对于某些密集的预测任务（例如语义分割）特别有用。我们公式的关键思想是通过比较每个编码器特征点与解码器特征的空间相关局部区域之间的相似性来生成相似性感知的内核。通过这种方式，编码器特征点可以作为提示，以告知UPS采样特征点的语义集群。为了体现该配方，我们进一步实例化了轻巧的增加采样算子，称为相似性 - 吸引点隶属关系（SAPA），并研究其变体。 SAPA会在许多密集的预测任务上邀请一致的性能改进，包括语义分割，对象检测，深度估计和图像垫。代码可用：https：//github.com/poppinace/sapa

在强化学习中，蒙特卡洛算法通过平均偶发回报来更新Q功能。在Monte Carlo UCB（MC-UCB）算法中，在每个状态下采取的动作是最大化Q函数加上UCB勘探项的动作，该术语偏向于选择频率较低的动作的选择。尽管在为MC-UCB建立遗憾界限方面已经进行了重要的工作，但大多数工作都集中在该问题的有限培训版本上，每个情节都在不断数量的步骤后终止。对于此类有限的Horizo​​n问题，最佳策略既取决于当前状态和情节中的时间。但是，对于许多自然的情节问题，例如GO，CHESS和机器人任务等游戏，该情节是随机的，最佳政策是静止的。对于此类环境，MC-UCB中的Q功能是否会收敛到最佳Q函数，这是一个空旷的问题。我们猜想，与Q学习不同，它并不是所有MDP的收敛。尽管如此，我们表明，对于大型MDP，其中包括二十一点和确定性MDP等随机MDP，例如GO，MC-UCB中的Q功能几乎可以肯定地收敛到最佳Q函数。该结果的直接推论是，它几乎肯定会为所有有限的Horizo​​n MDP收敛。我们还提供了数值实验，为MC-UCB提供了进一步的见解。