尽管最近通过剩余网络的代表学习中的自我监督方法取得了进展，但它们仍然对ImageNet分类基准进行了高度的监督学习，限制了它们在性能关键设置中的适用性。在MITROVIC等人的现有理论上洞察中建立2021年，我们提出了RELICV2，其结合了明确的不变性损失，在各种适当构造的数据视图上具有对比的目标。 Relicv2在ImageNet上实现了77.1％的前1个分类准确性，使用线性评估使用Reset50架构和80.6％，具有较大的Reset型号，优于宽边缘以前的最先进的自我监督方法。最值得注意的是，RelicV2是使用一系列标准Reset架构始终如一地始终优先于类似的对比较中的监督基线的第一个表示学习方法。最后，我们表明，尽管使用Reset编码器，Relicv2可与最先进的自我监控视觉变压器相媲美。

We introduce Bootstrap Your Own Latent (BYOL), a new approach to self-supervised image representation learning. BYOL relies on two neural networks, referred to as online and target networks, that interact and learn from each other. From an augmented view of an image, we train the online network to predict the target network representation of the same image under a different augmented view. At the same time, we update the target network with a slow-moving average of the online network. While state-of-the art methods rely on negative pairs, BYOL achieves a new state of the art without them. BYOL reaches 74.3% top-1 classification accuracy on ImageNet using a linear evaluation with a ResNet-50 architecture and 79.6% with a larger ResNet. We show that BYOL performs on par or better than the current state of the art on both transfer and semi-supervised benchmarks. Our implementation and pretrained models are given on GitHub. 3 * Equal contribution; the order of first authors was randomly selected.

自我监督学习的最新进展证明了多种视觉任务的有希望的结果。高性能自我监督方法中的一个重要成分是通过培训模型使用数据增强，以便在嵌入空间附近的相同图像的不同增强视图。然而，常用的增强管道整体地对待图像，忽略图像的部分的语义相关性-e.g。主题与背景 - 这可能导致学习杂散相关性。我们的工作通过调查一类简单但高度有效的“背景增强”来解决这个问题，这鼓励模型专注于语义相关内容，劝阻它们专注于图像背景。通过系统的调查，我们表明背景增强导致在各种任务中跨越一系列最先进的自我监督方法（MOCO-V2，BYOL，SWAV）的性能大量改进。 $ \ SIM $ + 1-2％的ImageNet收益，使得与监督基准的表现有关。此外，我们发现有限标签设置的改进甚至更大（高达4.2％）。背景技术增强还改善了许多分布换档的鲁棒性，包括天然对抗性实例，想象群-9，对抗性攻击，想象成型。我们还在产生了用于背景增强的显着掩模的过程中完全无监督的显着性检测进展。

Unsupervised image representations have significantly reduced the gap with supervised pretraining, notably with the recent achievements of contrastive learning methods. These contrastive methods typically work online and rely on a large number of explicit pairwise feature comparisons, which is computationally challenging. In this paper, we propose an online algorithm, SwAV, that takes advantage of contrastive methods without requiring to compute pairwise comparisons. Specifically, our method simultaneously clusters the data while enforcing consistency between cluster assignments produced for different augmentations (or "views") of the same image, instead of comparing features directly as in contrastive learning. Simply put, we use a "swapped" prediction mechanism where we predict the code of a view from the representation of another view. Our method can be trained with large and small batches and can scale to unlimited amounts of data. Compared to previous contrastive methods, our method is more memory efficient since it does not require a large memory bank or a special momentum network. In addition, we also propose a new data augmentation strategy, multi-crop, that uses a mix of views with different resolutions in place of two full-resolution views, without increasing the memory or compute requirements. We validate our findings by achieving 75.3% top-1 accuracy on ImageNet with ResNet-50, as well as surpassing supervised pretraining on all the considered transfer tasks.

We introduce Bootstrap Your Own Latent (BYOL), a new approach to selfsupervised image representation learning. BYOL relies on two neural networks, referred to as online and target networks, that interact and learn from each other. From an augmented view of an image, we train the online network to predict the target network representation of the same image under a different augmented view. At the same time, we update the target network with a slow-moving average of the online network. While state-of-the art methods rely on negative pairs, BYOL achieves a new state of the art without them. BYOL reaches 74.3% top-1 classification accuracy on ImageNet using a linear evaluation with a ResNet-50 architecture and 79.6% with a larger ResNet. We show that BYOL performs on par or better than the current state of the art on both transfer and semi-supervised benchmarks. Our implementation and pretrained models are given on GitHub. 3 * Equal contribution; the order of first authors was randomly selected. 3

This paper presents SimCLR: a simple framework for contrastive learning of visual representations. We simplify recently proposed contrastive selfsupervised learning algorithms without requiring specialized architectures or a memory bank. In order to understand what enables the contrastive prediction tasks to learn useful representations, we systematically study the major components of our framework. We show that (1) composition of data augmentations plays a critical role in defining effective predictive tasks, (2) introducing a learnable nonlinear transformation between the representation and the contrastive loss substantially improves the quality of the learned representations, and (3) contrastive learning benefits from larger batch sizes and more training steps compared to supervised learning. By combining these findings, we are able to considerably outperform previous methods for self-supervised and semi-supervised learning on ImageNet. A linear classifier trained on self-supervised representations learned by Sim-CLR achieves 76.5% top-1 accuracy, which is a 7% relative improvement over previous state-ofthe-art, matching the performance of a supervised ResNet-50. When fine-tuned on only 1% of the labels, we achieve 85.8% top-5 accuracy, outperforming AlexNet with 100× fewer labels. 1

最近无监督的表示学习方法已经通过学习表示不变的数据增强，例如随机裁剪和彩色抖动等数据增强来生效。然而，如果依赖于数据增强的特征，例如，位置或色敏，则这种不变性可能对下游任务有害。这不是一个不监督学习的问题;我们发现即使在监督学习中也会发生这种情况，因为它还学会预测实例所有增强样本的相同标签。为避免此类失败并获得更广泛的表示，我们建议优化辅助自我监督损失，创建的AGESELF，了解两个随机增强样本之间的增强参数（例如，裁剪位置，颜色调整强度）的差异。我们的直觉是，Augelf鼓励在学习的陈述中保留增强信息，这可能有利于其可转让性。此外，Augself可以很容易地纳入最近的最先进的表示学习方法，其额外的培训成本可忽略不计。广泛的实验表明，我们的简单想法一直在各种转移学习情景中始终如一地提高了由监督和无监督方法所学到的表示的可转移性。代码可在https://github.com/hankook/augsfir。

学习概括不见于没有人类监督的有效视觉表现是一个基本问题，以便将机器学习施加到各种各样的任务。最近，分别是SIMCLR和BYOL的两个自我监督方法，对比学习和潜在自动启动的家庭取得了重大进展。在这项工作中，我们假设向这些算法添加显式信息压缩产生更好，更强大的表示。我们通过开发与条件熵瓶颈（CEB）目标兼容的SIMCLR和BYOL配方来验证这一点，允许我们衡量并控制学习的表示中的压缩量，并观察它们对下游任务的影响。此外，我们探讨了Lipschitz连续性和压缩之间的关系，显示了我们学习的编码器的嘴唇峰常数上的易触摸下限。由于Lipschitz连续性与稳健性密切相关，这为什么压缩模型更加强大提供了新的解释。我们的实验证实，向SIMCLR和BYOL添加压缩显着提高了线性评估精度和模型鲁棒性，跨各种域移位。特别是，Byol的压缩版本与Reset-50的ImageNet上的76.0％的线性评估精度达到了76.0％的直线评价精度，并使用Reset-50 2x的78.8％。

对比度学习最近在无监督的视觉表示学习中显示出巨大的潜力。在此轨道中的现有研究主要集中于图像内不变性学习。学习通常使用丰富的图像内变换来构建正对，然后使用对比度损失最大化一致性。相反，相互影响不变性的优点仍然少得多。利用图像间不变性的一个主要障碍是，尚不清楚如何可靠地构建图像间的正对，并进一步从它们中获得有效的监督，因为没有配对注释可用。在这项工作中，我们提出了一项全面的实证研究，以更好地了解从三个主要组成部分的形象间不变性学习的作用：伪标签维护，采样策略和决策边界设计。为了促进这项研究，我们引入了一个统一的通用框架，该框架支持无监督的内部和间形内不变性学习的整合。通过精心设计的比较和分析，揭示了多个有价值的观察结果：1）在线标签收敛速度比离线标签更快； 2）半硬性样品比硬否定样品更可靠和公正； 3）一个不太严格的决策边界更有利于形象间的不变性学习。借助所有获得的食谱，我们的最终模型（即InterCLR）对多个标准基准测试的最先进的内图内不变性学习方法表现出一致的改进。我们希望这项工作将为设计有效的无监督间歇性不变性学习提供有用的经验。代码：https：//github.com/open-mmlab/mmselfsup。

通过自学学习的视觉表示是一项极具挑战性的任务，因为网络需要在没有监督提供的主动指导的情况下筛选出相关模式。这是通过大量数据增强，大规模数据集和过量量的计算来实现的。视频自我监督学习（SSL）面临着额外的挑战：视频数据集通常不如图像数据集那么大，计算是一个数量级，并且优化器所必须通过的伪造模式数量乘以几倍。因此，直接从视频数据中学习自我监督的表示可能会导致次优性能。为了解决这个问题，我们建议在视频表示学习框架中利用一个以自我或语言监督为基础的强大模型，并在不依赖视频标记的数据的情况下学习强大的空间和时间信息。为此，我们修改了典型的基于视频的SSL设计和目标，以鼓励视频编码器\ textit {subsume}基于图像模型的语义内容，该模型在通用域上训练。所提出的算法被证明可以更有效地学习（即在较小的时期和较小的批次中），并在单模式SSL方法中对标准下游任务进行了新的最新性能。

自我监督学习（SSL）的承诺是利用大量未标记的数据来解决复杂的任务。尽管简单，图像级学习取得了出色的进步，但最新方法显示出包括图像结构知识的优势。但是，通过引入手工制作的图像分割来定义感兴趣的区域或专门的增强策略，这些方法牺牲了使SSL如此强大的简单性和通用性。取而代之的是，我们提出了一个自我监督的学习范式，该学习范式本身会发现这种图像结构。我们的方法，ODIN，夫妻对象发现和表示网络，以发现有意义的图像分割，而无需任何监督。由此产生的学习范式更简单，更易碎，更一般，并且取得了最先进的转移学习结果，以进行对象检测和实例对可可的细分，以及对Pascal和CityScapes的语义细分，同时超过监督的预先培训，用于戴维斯的视频细分。

Contrastive learning applied to self-supervised representation learning has seen a resurgence in recent years, leading to state of the art performance in the unsupervised training of deep image models. Modern batch contrastive approaches subsume or significantly outperform traditional contrastive losses such as triplet, max-margin and the N-pairs loss. In this work, we extend the self-supervised batch contrastive approach to the fully-supervised setting, allowing us to effectively leverage label information. Clusters of points belonging to the same class are pulled together in embedding space, while simultaneously pushing apart clusters of samples from different classes. We analyze two possible versions of the supervised contrastive (SupCon) loss, identifying the best-performing formulation of the loss. On ResNet-200, we achieve top-1 accuracy of 81.4% on the Ima-geNet dataset, which is 0.8% above the best number reported for this architecture. We show consistent outperformance over cross-entropy on other datasets and two ResNet variants. The loss shows benefits for robustness to natural corruptions, and is more stable to hyperparameter settings such as optimizers and data augmentations. Our loss function is simple to implement and reference TensorFlow code is released at https://t.ly/supcon 1 .

我们提出了自适应培训 - 一种统一的培训算法，通过模型预测动态校准并增强训练过程，而不会产生额外的计算成本 - 以推进深度神经网络的监督和自我监督的学习。我们分析了培训数据的深网络培训动态，例如随机噪声和对抗例。我们的分析表明，模型预测能够在数据中放大有用的基础信息，即使在没有任何标签信息的情况下，这种现象也会发生，突出显示模型预测可能会产生培训过程：自适应培训改善了深网络的概括在噪音下，增强自我监督的代表学习。分析还阐明了解深度学习，例如，在经验风险最小化和最新的自我监督学习算法的折叠问题中对最近发现的双重现象的潜在解释。在CIFAR，STL和Imagenet数据集上的实验验证了我们在三种应用中的方法的有效性：用标签噪声，选择性分类和线性评估进行分类。为了促进未来的研究，该代码已在HTTPS://github.com/layneh/Self-Aveptive-训练中公开提供。

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.

Contrastive learning has become a key component of self-supervised learning approaches for computer vision. By learning to embed two augmented versions of the same image close to each other and to push the embeddings of different images apart, one can train highly transferable visual representations. As revealed by recent studies, heavy data augmentation and large sets of negatives are both crucial in learning such representations. At the same time, data mixing strategies, either at the image or the feature level, improve both supervised and semi-supervised learning by synthesizing novel examples, forcing networks to learn more robust features. In this paper, we argue that an important aspect of contrastive learning, i.e. the effect of hard negatives, has so far been neglected. To get more meaningful negative samples, current top contrastive self-supervised learning approaches either substantially increase the batch sizes, or keep very large memory banks; increasing memory requirements, however, leads to diminishing returns in terms of performance. We therefore start by delving deeper into a top-performing framework and show evidence that harder negatives are needed to facilitate better and faster learning. Based on these observations, and motivated by the success of data mixing, we propose hard negative mixing strategies at the feature level, that can be computed on-the-fly with a minimal computational overhead. We exhaustively ablate our approach on linear classification, object detection, and instance segmentation and show that employing our hard negative mixing procedure improves the quality of visual representations learned by a state-of-the-art self-supervised learning method.Project page: https://europe.naverlabs.com/mochi 34th Conference on Neural Information Processing Systems (NeurIPS 2020),

对比自我监督的学习已经超越了许多下游任务的监督预测，如分割和物体检测。但是，当前的方法仍然主要应用于像想象成的策划数据集。在本文中，我们首先研究数据集中的偏差如何影响现有方法。我们的研究结果表明，目前的对比方法令人惊讶地工作：（i）对象与场景为中心，（ii）统一与长尾和（iii）一般与域特定的数据集。其次，鉴于这种方法的一般性，我们尝试通过微小的修改来实现进一步的收益。我们展示了学习额外的修正 - 通过使用多尺度裁剪，更强的增强和最近的邻居 - 改善了表示。最后，我们观察Moco在用多作物策略训练时学习空间结构化表示。表示可以用于语义段检索和视频实例分段，而不会FineTuning。此外，结果与专门模型相提并论。我们希望这项工作将成为其他研究人员的有用研究。代码和模型可在https://github.com/wvanganebleke/revisiting-contrastive-ssl上获得。

变形金刚和蒙版语言建模在计算机视觉中很快被视为视觉变压器和蒙版图像建模（MIM）。在这项工作中，我们认为由于图像中令牌的数量和相关性，图像令牌掩盖与文本中的令牌掩盖有所不同。特别是，为了为MIM产生具有挑战性的借口任务，我们主张从随机掩盖到知情掩盖的转变。我们在基于蒸馏的MIM的背景下开发并展示了这一想法，其中教师变压器编码器生成了一个注意力图，我们用它来指导学生为学生指导掩盖。因此，我们引入了一种新颖的掩蔽策略，称为注意引导蒙版（ATTMASK），我们证明了其对基于密集蒸馏的MIM以及基于普通蒸馏的自然剥离的自助力学习的有效性。我们确认ATTMASK可以加快学习过程，并提高各种下游任务的性能。我们在https://github.com/gkakogeorgiou/attmask上提供实现代码。

自我监督学习中的最新作品通过以对象为中心或基于区域的对应目标进行预处理，在场景级密集的预测任务上表现出了强劲的表现。在本文中，我们介绍了区域对象表示学习（R2O），该学习统一了基于区域的和以对象为中心的预处理。 R2O通过训练编码器以动态完善基于区域的段为中心的蒙版，然后共同学习掩模中内容的表示形式。 R2O使用“区域改进模块”将使用区域级先验生成的小图像区域分组为较大的区域，这些区域倾向于通过聚类区域级特征对应对应对象。随着训练的进展，R2O遵循了一个区域到对象的课程，该课程鼓励学习区域级的早期特征并逐渐进步以训练以对象为中心的表示。使用R2O的表示形式导致了Pascal VOC（+0.7 MIOU）和CityScapes（+0.4 MIOU）的语义细分表现最先进的表现，并在MS Coco（+0.3 Mask AP）上进行了实例细分。此外，在对Imagenet进行了预审进之后，R2O预处理的模型能够超过Caltech-UCSD Birds 200-2011数据集（+2.9 MIOU）的无监督物体细分中现有的最新对象细分。我们在https://github.com/kkallidromitis/r2o上提供了这项工作的代码/模型。

Self-supervised visual representation learning has seen huge progress recently, but no large scale evaluation has compared the many models now available. We evaluate the transfer performance of 13 top self-supervised models on 40 downstream tasks, including many-shot and few-shot recognition, object detection, and dense prediction. We compare their performance to a supervised baseline and show that on most tasks the best self-supervised models outperform supervision, confirming the recently observed trend in the literature. We find ImageNet Top-1 accuracy to be highly correlated with transfer to many-shot recognition, but increasingly less so for few-shot, object detection and dense prediction. No single self-supervised method dominates overall, suggesting that universal pre-training is still unsolved. Our analysis of features suggests that top self-supervised learners fail to preserve colour information as well as supervised alternatives, but tend to induce better classifier calibration, and less attentive overfitting than supervised learners.