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Poster
OpenMatch: Open-Set Semi-supervised Learning with Open-set Consistency Regularization
Kuniaki Saito · Donghyun Kim · Kate Saenko

Thu Dec 09 08:30 AM -- 10:00 AM (PST) @
in Poster Session 6 »

Semi-supervised learning (SSL) is an effective means to leverage unlabeled data to improve a model’s performance. Typical SSL methods like FixMatch assume that labeled and unlabeled data share the same label space. However, in practice, unlabeled data can contain categories unseen in the labeled set, i.e., outliers, which can significantly harm the performance of SSL algorithms. To address this problem, we propose a novel Open-set Semi-Supervised Learning (OSSL) approach called OpenMatch.Learning representations of inliers while rejecting outliers is essential for the success of OSSL. To this end, OpenMatch unifies FixMatch with novelty detection based on one-vs-all (OVA) classifiers. The OVA-classifier outputs the confidence score of a sample being an inlier, providing a threshold to detect outliers. Another key contribution is an open-set soft-consistency regularization loss, which enhances the smoothness of the OVA-classifier with respect to input transformations and greatly improves outlier detection. \ours achieves state-of-the-art performance on three datasets, and even outperforms a fully supervised model in detecting outliers unseen in unlabeled data on CIFAR10. The code is available at \url{https://github.com/VisionLearningGroup/OP_Match}.

Keywords: Semi-Supervised Learning

Author Information

Kuniaki Saito (Boston University)
Donghyun Kim (Boston University)
Kate Saenko (Boston University & MIT-IBM Watson AI Lab, IBM Research)

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