Unsupervised domain adaptation for classification tasks has achieved great progress in leveraging the knowledge in a labeled (source) domain to improve the task performance in an unlabeled (target) domain by mitigating the effect of distribution discrepancy. However, most existing methods can only handle unsupervised closed set domain adaptation (UCSDA), where the source and target domains share the same label set. In this paper, we target a more challenging but realistic setting: unsupervised open set domain adaptation (UOSDA), where the target domain has unknown classes that the source domain does not have. This study is the first to give the generalization bound of open set domain adaptation through theoretically investigating the risk of the target classifier on the unknown classes. The proposed generalization bound for open set domain adaptation has a special term, namely open set difference, which reflects the risk of the target classifier on unknown classes. According to this generalization bound, we propose a novel and theoretically guided unsupervised open set domain adaptation method: Distribution Alignment with Open Difference (DAOD), which is based on the structural risk minimization principle and open set difference regularization. The experiments on several benchmark datasets show the superior performance of the proposed UOSDA method compared with the state-of-the-art methods in the literature.
When the source domain and target domain for known classes share the same distribution, the open set domain adaptation becomes . A common method for handling open set recognition relies on the use of threshold-based classification strategies @cite_30 . Establishing a threshold on the similarity score means rejecting distant samples from the training samples. (OSNN) @cite_36 recognizes whether a sample is from unknown classes by comparing the threshold with the ratio of similarity scores to the two most similar classes of the sample. Another trend relies on modifying (SVM) @cite_5 @cite_39 @cite_16 . (OSVM) @cite_16 uses a multi-class SVM as a basis to learn the unnormalized posterior probability which is used to reject unknown samples.
@cite_30 @cite_36 @cite_39 @cite_5 @cite_16
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The heart of designing and conducting evaluations and is the experimental protocol. The protocol states how an evaluation is to be conducted and how the results are to be computed. In this chapter we concentrate on describing the FERET and FRVT 2002 protocols. The FRVT 2002 evaluation protocol is based in the FERET evaluation protocols. The FRVT 2002 protocol is designed for biometric evaluations in general, not just for evaluating face recognition algorithms. These two evaluation protocol served as a basis for the FRVT 2006 and MBE 2010 evaluations. In this paper, we propose a novel multiclass classifier for the open-set recognition scenario. This scenario is the one in which there are no a priori training samples for some classes that might appear during testing. Usually, many applications are inherently open set. Consequently, successful closed-set solutions in the literature are not always suitable for real-world recognition problems. The proposed open-set classifier extends upon the Nearest-Neighbor (NN) classifier. Nearest neighbors are simple, parameter independent, multiclass, and widely used for closed-set problems. The proposed Open-Set NN (OSNN) method incorporates the ability of recognizing samples belonging to classes that are unknown at training time, being suitable for open-set recognition. In addition, we explore evaluation measures for open-set problems, properly measuring the resilience of methods to unknown classes during testing. For validation, we consider large freely-available benchmarks with different open-set recognition regimes and demonstrate that the proposed OSNN significantly outperforms their counterparts in the literature. Face Recognition is one of the most relevant problems in computer vision as we consider its importance to areas such as surveillance, forensics and psychology. Furthermore, open-set face recognition has a large room for improvement since only few researchers have focused on it. In fact, a real-world recognition system has to cope with several unseen individuals and determine whether a given face image is associated with a subject registered in a gallery of known individuals. In this work, we combine hashing functions and classification methods to estimate when probe samples are known (i.e., belong to the gallery set). We carry out experiments with partial least squares and neural networks and show how response value histograms tend to behave for known and unknown individuals whenever we test a probe sample. In addition, we conduct experiments on FRGCv1, PubFig83 and VGGFace to show that our method continues effective regardless of the dataset difficulty. Real-world tasks in computer vision often touch upon open set recognition: multi-class recognition with incomplete knowledge of the world and many unknown inputs. Recent work on this problem has proposed a model incorporating an open space risk term to account for the space beyond the reasonable support of known classes. This paper extends the general idea of open space risk limiting classification to accommodate non-linear classifiers in a multiclass setting. We introduce a new open set recognition model called compact abating probability (CAP), where the probability of class membership decreases in value (abates) as points move from known data toward open space. We show that CAP models improve open set recognition for multiple algorithms. Leveraging the CAP formulation, we go on to describe the novel Weibull-calibrated SVM (W-SVM) algorithm, which combines the useful properties of statistical extreme value theory for score calibration with one-class and binary support vector machines. Our experiments show that the W-SVM is significantly better for open set object detection and OCR problems when compared to the state-of-the-art for the same tasks. The perceived success of recent visual recognition approaches has largely been derived from their performance on classification tasks, where all possible classes are known at training time. But what about open set problems, where unknown classes appear at test time? Intuitively, if we could accurately model just the positive data for any known class without overfitting, we could reject the large set of unknown classes even under an assumption of incomplete class knowledge. In this paper, we formulate the problem as one of modeling positive training data at the decision boundary, where we can invoke the statistical extreme value theory. A new algorithm called the P I -SVM is introduced for estimating the unnormalized posterior probability of class inclusion.