无监督域适应的最新进步已经表明，通过提取域不变表示来缓解域分流可以显着改善模型的概括到未标记的数据域。然而，现有方法未能有效保留私有的标签缺失域的表示，这可能会对概括产生不利影响。在本文中，我们提出了一种保留这种表示的方法，使得未标记域的潜在分布可以代表域不变的功能和私有到未标记域的各个特征。特别地，我们证明，在减轻域分歧的同时最大化未标记的域和其潜空间之间的相互信息可以实现这种保存。我们也理论上和经验验证的验证验证，保留私有到未标记的域的表示是重要的，并且是跨域泛化的必要性。我们的方法优于几个公共数据集上的最先进的方法。

虽然在许多域内生成并提供了大量的未标记数据，但对视觉数据的自动理解的需求高于以往任何时候。大多数现有机器学习模型通常依赖于大量标记的训练数据来实现高性能。不幸的是，在现实世界的应用中，不能满足这种要求。标签的数量有限，手动注释数据昂贵且耗时。通常需要将知识从现有标记域传输到新域。但是，模型性能因域之间的差异（域移位或数据集偏差）而劣化。为了克服注释的负担，域适应（DA）旨在在将知识从一个域转移到另一个类似但不同的域中时减轻域移位问题。无监督的DA（UDA）处理标记的源域和未标记的目标域。 UDA的主要目标是减少标记的源数据和未标记的目标数据之间的域差异，并在培训期间在两个域中学习域不变的表示。在本文中，我们首先定义UDA问题。其次，我们从传统方法和基于深度学习的方法中概述了不同类别的UDA的最先进的方法。最后，我们收集常用的基准数据集和UDA最先进方法的报告结果对视觉识别问题。

对抗性学习策略在处理单源域适应（DA）问题时表现出显着的性能，并且最近已应用于多源DA（MDA）问题。虽然大多数现有的MDA策略依赖于多个域歧视员设置，但其对潜伏空间表示的影响已经不知识。在这里，我们采用了一种信息 - 理论方法来识别和解决MDA上多个域鉴别器的潜在不利影响：域歧视信息的解体，有限的计算可扩展性以及培训期间损失梯度的大方差。我们在信息正规化的背景下通过情况进行对抗性DA来检查上述问题。这还提供了使用单一和统一域鉴别器的理论正当理由。基于这个想法，我们实施了一种名为多源信息正规化适应网络（MIAN）的新型神经结构。大规模实验表明，尽管其结构简洁，可靠，可显着优于其他最先进的方法。

Unsupervised domain adaptation (UDA) aims to transfer knowledge from a well-labeled source domain to a different but related unlabeled target domain with identical label space. Currently, the main workhorse for solving UDA is domain alignment, which has proven successful. However, it is often difficult to find an appropriate source domain with identical label space. A more practical scenario is so-called partial domain adaptation (PDA) in which the source label set or space subsumes the target one. Unfortunately, in PDA, due to the existence of the irrelevant categories in the source domain, it is quite hard to obtain a perfect alignment, thus resulting in mode collapse and negative transfer. Although several efforts have been made by down-weighting the irrelevant source categories, the strategies used tend to be burdensome and risky since exactly which irrelevant categories are unknown. These challenges motivate us to find a relatively simpler alternative to solve PDA. To achieve this, we first provide a thorough theoretical analysis, which illustrates that the target risk is bounded by both model smoothness and between-domain discrepancy. Considering the difficulty of perfect alignment in solving PDA, we turn to focus on the model smoothness while discard the riskier domain alignment to enhance the adaptability of the model. Specifically, we instantiate the model smoothness as a quite simple intra-domain structure preserving (IDSP). To our best knowledge, this is the first naive attempt to address the PDA without domain alignment. Finally, our empirical results on multiple benchmark datasets demonstrate that IDSP is not only superior to the PDA SOTAs by a significant margin on some benchmarks (e.g., +10% on Cl->Rw and +8% on Ar->Rw ), but also complementary to domain alignment in the standard UDA

与标准闭合域的适应任务相反，部分域适应设置通过放松相同的标签集假设来迎合现实情况。但是，源标签集集成了目标标签集的事实，因此引入了一些额外的障碍，因为私人源类别样本的培训阻止了相关的知识转移并误导了分类过程。为了减轻这些问题，我们设计了一种机制，用于策略选择高度自信的目标样本，这对于估算班级的体重所必需的必不可少的机制。此外，我们通过将实现紧凑型和不同类别分布的过程与对抗性目标结合过程来捕获类歧视和域的不变特征。对众多跨域分类任务的实验发现证明了所提出的技术具有比现有方法具有卓越和可比精度的潜力。

学习目标域中的未知样本（不存在于源类中）对于无监督域适应（UDA）相当重要。存在两个典型的UDA方案，即开放式和开放式集合，后者假定目标域中并非所有源类都显示在内。但是，大多数先前的方法都是为一个UDA场景而设计的，并且始终在其他UDA方案上表现差。此外，它们还需要在适应过程中标记的源数据，限制其在数据隐私敏感应用中的可用性。为了解决这些问题，本文提出了一种通用模型适应（UMAD）框架，其处理了UDA方案，而无需访问源数据，也不是关于域之间类别的类别的知识。具体而言，我们的目标是使用优雅设计的双头分类器来学习源模型，并将其提供给目标域。在适应期间，我们开发了一种信息丰富的一致性分数，以帮助区分从已知样品中的未知样本。为了在目标域中实现双边适应，我们进一步最大化了局部化的相互信息，以将已知的样本与源分类器对齐，并采用熵丢失，以便分别推动远离源分类边界的未知样本。开放式和开放式的UDA方案的实验表明，umad作为无需访问源数据的统一方法，展示与最先进的数据相关方法的可比性。

无监督域适配利用标记的源域中丰富的信息来模拟未标记的目标域。现有方法尝试对齐跨域分布。然而，两个域的对准的统计表示并不良好解决。在本文中，我们提出了深度最小二乘对准（DLSA）来估计通过参数化线性模型来估计潜在空间中的两个域的分布。我们通过最小化拟合线和截距差异之间的角度以及进一步学习域不变特征，进一步开发边缘和条件适应损失以减少域差异。广泛的实验表明，所提出的DLSA模型在对准域分布和优于最先进的方法方面有效。

The standard closed-set domain adaptation approaches seek to mitigate distribution discrepancies between two domains under the constraint of both sharing identical label sets. However, in realistic scenarios, finding an optimal source domain with identical label space is a challenging task. Partial domain adaptation alleviates this problem of procuring a labeled dataset with identical label space assumptions and addresses a more practical scenario where the source label set subsumes the target label set. This, however, presents a few additional obstacles during adaptation. Samples with categories private to the source domain thwart relevant knowledge transfer and degrade model performance. In this work, we try to address these issues by coupling variational information and adversarial learning with a pseudo-labeling technique to enforce class distribution alignment and minimize the transfer of superfluous information from the source samples. The experimental findings in numerous cross-domain classification tasks demonstrate that the proposed technique delivers superior and comparable accuracy to existing methods.

在图像分类中，获得足够的标签通常昂贵且耗时。为了解决这个问题，域适应通常提供有吸引力的选择，给出了来自类似性质但不同域的大量标记数据。现有方法主要对准单个结构提取的表示的分布，并且表示可以仅包含部分信息，例如，仅包含部分饱和度，亮度和色调信息。在这一行中，我们提出了多代表性适应，这可以大大提高跨域图像分类的分类精度，并且特别旨在对准由名为Inception Adaption Adationation模块（IAM）提取的多个表示的分布。基于此，我们呈现多色自适应网络（MRAN）来通过多表示对准完成跨域图像分类任务，该任向性可以捕获来自不同方面的信息。此外，我们扩展了最大的平均差异（MMD）来计算适应损耗。我们的方法可以通过扩展具有IAM的大多数前进模型来轻松实现，并且网络可以通过反向传播有效地培训。在三个基准图像数据集上进行的实验证明了备的有效性。代码已在https://github.com/easezyc/deep-transfer -learning上获得。

Domain adaptation enables the learner to safely generalize into novel environments by mitigating domain shifts across distributions. Previous works may not effectively uncover the underlying reasons that would lead to the drastic model degradation on the target task. In this paper, we empirically reveal that the erratic discrimination of the target domain mainly stems from its much smaller feature norms with respect to that of the source domain. To this end, we propose a novel parameter-free Adaptive Feature Norm approach. We demonstrate that progressively adapting the feature norms of the two domains to a large range of values can result in significant transfer gains, implying that those task-specific features with larger norms are more transferable. Our method successfully unifies the computation of both standard and partial domain adaptation with more robustness against the negative transfer issue. Without bells and whistles but a few lines of code, our method substantially lifts the performance on the target task and exceeds state-of-the-arts by a large margin (11.5% on Office-Home [45] and 17.1% on VisDA2017 [31]). We hope our simple yet effective approach will shed some light on the future research of transfer learning. Code is available at https://github.com/jihanyang/AFN .

Domain adaptation aims at generalizing a high-performance learner on a target domain via utilizing the knowledge distilled from a source domain which has a different but related data distribution. One solution to domain adaptation is to learn domain invariant feature representations while the learned representations should also be discriminative in prediction. To learn such representations, domain adaptation frameworks usually include a domain invariant representation learning approach to measure and reduce the domain discrepancy, as well as a discriminator for classification. Inspired by Wasserstein GAN, in this paper we propose a novel approach to learn domain invariant feature representations, namely Wasserstein Distance Guided Representation Learning (WD-GRL). WDGRL utilizes a neural network, denoted by the domain critic, to estimate empirical Wasserstein distance between the source and target samples and optimizes the feature extractor network to minimize the estimated Wasserstein distance in an adversarial manner. The theoretical advantages of Wasserstein distance for domain adaptation lie in its gradient property and promising generalization bound. Empirical studies on common sentiment and image classification adaptation datasets demonstrate that our proposed WDGRL outperforms the state-of-the-art domain invariant representation learning approaches.

无监督域适应（UDA）旨在将知识从相关但不同的良好标记的源域转移到新的未标记的目标域。大多数现有的UDA方法需要访问源数据，因此当数据保密而不相配在隐私问题时，不适用。本文旨在仅使用培训的分类模型来解决现实设置，而不是访问源数据。为了有效地利用适应源模型，我们提出了一种新颖的方法，称为源假设转移（拍摄），其通过将目标数据特征拟合到冻结源分类模块（表示分类假设）来学习目标域的特征提取模块。具体而言，拍摄挖掘出于特征提取模块的信息最大化和自我监督学习，以确保目标特征通过同一假设与看不见的源数据的特征隐式对齐。此外，我们提出了一种新的标签转移策略，它基于预测的置信度（标签信息），然后采用半监督学习来将目标数据分成两个分裂，然后提高目标域中的较为自信预测的准确性。如果通过拍摄获得预测，我们表示标记转移为拍摄++。关于两位数分类和对象识别任务的广泛实验表明，拍摄和射击++实现了与最先进的结果超越或相当的结果，展示了我们对各种视域适应问题的方法的有效性。代码可用于\ url {https：//github.com/tim-learn/shot-plus}。

Adversarial learning has been embedded into deep networks to learn disentangled and transferable representations for domain adaptation. Existing adversarial domain adaptation methods may not effectively align different domains of multimodal distributions native in classification problems. In this paper, we present conditional adversarial domain adaptation, a principled framework that conditions the adversarial adaptation models on discriminative information conveyed in the classifier predictions. Conditional domain adversarial networks (CDANs) are designed with two novel conditioning strategies: multilinear conditioning that captures the crosscovariance between feature representations and classifier predictions to improve the discriminability, and entropy conditioning that controls the uncertainty of classifier predictions to guarantee the transferability. With theoretical guarantees and a few lines of codes, the approach has exceeded state-of-the-art results on five datasets.

域适应（da）尝试将知识从标记的源域传输到从源的不同分发的未标记的目标域。为此，DA方法包括源分类目标，以提取源知识和域对齐目标以减少域移位，确保知识转移。通常，前DA方法采用一些重量的超参数来线性地结合培训目标来形成整体目标。然而，由于域移位，这些目标的梯度方向可能彼此冲突。在这种情况下，线性优化方案可能会降低整体目标值，以损坏其中一个培训目标，导致限制解决方案。在本文中，我们从基于梯度的角度来看了DA的优化方案。我们提出了帕累托域适应（Paretoda）方法来控制整体优化方向，旨在协同优化所有培训目标。具体地，为了达到目标域的理想解决方案，我们设计了模拟目标分类的替代损失。为了提高目标预测准确性以支持模拟，我们提出了一种目标预测精炼机制，其通过贝叶斯定理利用域标签。另一方面，由于对象的加权方案的先验知识通常无法指导优化来接近目标域上的最佳解决方案，因此我们提出了一种动态的偏好机制，以动态指导我们的合作优化通过替代损失的梯度保持未标记的目标数据集。关于图像分类和语义分割基准的广泛实验证明了Paretoda的有效性

This paper addresses the problem of unsupervised domain adaption from theoretical and algorithmic perspectives. Existing domain adaptation theories naturally imply minimax optimization algorithms, which connect well with the domain adaptation methods based on adversarial learning. However, several disconnections still exist and form the gap between theory and algorithm. We extend previous theories (Mansour et al., 2009c;Ben-David et al., 2010) to multiclass classification in domain adaptation, where classifiers based on the scoring functions and margin loss are standard choices in algorithm design. We introduce Margin Disparity Discrepancy, a novel measurement with rigorous generalization bounds, tailored to the distribution comparison with the asymmetric margin loss, and to the minimax optimization for easier training. Our theory can be seamlessly transformed into an adversarial learning algorithm for domain adaptation, successfully bridging the gap between theory and algorithm. A series of empirical studies show that our algorithm achieves the state of the art accuracies on challenging domain adaptation tasks.

虽然无监督的域适应（UDA）算法，即，近年来只有来自源域的标记数据，大多数算法和理论结果侧重于单源无监督域适应（SUDA）。然而，在实际情况下，标记的数据通常可以从多个不同的源收集，并且它们可能不仅不同于目标域而且彼此不同。因此，来自多个源的域适配器不应以相同的方式进行建模。最近基于深度学习的多源无监督域适应（Muda）算法专注于通过在通用特征空间中的所有源极和目标域的分布对齐来提取所有域的公共域不变表示。但是，往往很难提取Muda中所有域的相同域不变表示。此外，这些方法匹配分布而不考虑类之间的域特定的决策边界。为了解决这些问题，我们提出了一个新的框架，具有两个对准阶段的Muda，它不仅将每对源和目标域的分布对齐，而且还通过利用域特定的分类器的输出对准决策边界。广泛的实验表明，我们的方法可以对图像分类的流行基准数据集实现显着的结果。

Unsupervised domain adaptation (UDA) aims to leverage the knowledge learned from a labeled source dataset to solve similar tasks in a new unlabeled domain. Prior UDA methods typically require to access the source data when learning to adapt the model, making them risky and inefficient for decentralized private data. This work tackles a practical setting where only a trained source model is available and investigates how we can effectively utilize such a model without source data to solve UDA problems. We propose a simple yet generic representation learning framework, named Source HypOthesis Transfer (SHOT). SHOT freezes the classifier module (hypothesis) of the source model and learns the target-specific feature extraction module by exploiting both information maximization and selfsupervised pseudo-labeling to implicitly align representations from the target domains to the source hypothesis. To verify its versatility, we evaluate SHOT in a variety of adaptation cases including closed-set, partial-set, and open-set domain adaptation. Experiments indicate that SHOT yields state-of-the-art results among multiple domain adaptation benchmarks.

We propose a novel unsupervised domain adaptation framework based on domain-specific batch normalization in deep neural networks. We aim to adapt to both domains by specializing batch normalization layers in convolutional neural networks while allowing them to share all other model parameters, which is realized by a twostage algorithm. In the first stage, we estimate pseudolabels for the examples in the target domain using an external unsupervised domain adaptation algorithm-for example, MSTN [27] or CPUA [14]-integrating the proposed domain-specific batch normalization. The second stage learns the final models using a multi-task classification loss for the source and target domains. Note that the two domains have separate batch normalization layers in both stages. Our framework can be easily incorporated into the domain adaptation techniques based on deep neural networks with batch normalization layers. We also present that our approach can be extended to the problem with multiple source domains. The proposed algorithm is evaluated on multiple benchmark datasets and achieves the state-of-theart accuracy in the standard setting and the multi-source domain adaption scenario.

域的适应性（DA）旨在将知识从标记的源域中学习的知识转移到未标记或标记较小但相关的目标域的知识。理想情况下，源和目标分布应彼此平等地对齐，以实现公正的知识转移。但是，由于源和目标域中注释数据的数量之间存在显着不平衡，通常只有目标分布与源域保持一致，从而使不必要的源特定知识适应目标域，即偏置域的适应性。为了解决此问题，在这项工作中，我们通过对基于对抗性的DA方法进行建模来对歧视器的不确定性进行建模，以优化无偏见转移。我们理论上分析了DA中提出的无偏可传递性学习方法的有效性。此外，为了减轻注释数据不平衡的影响，我们利用了目标域中未标记样品的伪标签选择的估计不确定性，这有助于实现更好的边际和条件分布在域之间的分布。对各种DA基准数据集的广泛实验结果表明，可以轻松地将所提出的方法纳入各种基于对抗性的DA方法中，从而实现最新的性能。

无监督的域适应性（DA）中的主要挑战是减轻源域和目标域之间的域移动。先前的DA工作表明，可以使用借口任务来通过学习域不变表示来减轻此域的转移。但是，实际上，我们发现大多数现有的借口任务对其他已建立的技术无效。因此，我们从理论上分析了如何以及何时可以利用子公司借口任务来协助给定DA问题的目标任务并制定客观的子公司任务适用性标准。基于此标准，我们设计了一个新颖的贴纸干预过程和铸造贴纸分类的过程，作为监督的子公司DA问题，该问题与目标任务无监督的DA同时发生。我们的方法不仅改善了目标任务适应性能，而且还促进了面向隐私的无源DA，即没有并发源目标访问。标准Office-31，Office-Home，Domainnet和Visda基准的实验证明了我们对单源和多源无源DA的优势。我们的方法还补充了现有的无源作品，从而实现了领先的绩效。