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Discriminatively trained neural classifiers can be trusted, only when the input data comes from the training distribution (in-distribution). Therefore, detecting out-of-distribution (OOD) samples is very important to avoid classification…

Machine Learning · Computer Science 2019-04-30 Sachin Vernekar , Ashish Gaurav , Taylor Denouden , Buu Phan , Vahdat Abdelzad , Rick Salay , Krzysztof Czarnecki

Deep generative models aim to learn underlying distributions that generate the observed data. Given the fact that the generative distribution may be complex and intractable, deep latent variable models use probabilistic frameworks to learn…

Machine Learning · Computer Science 2021-10-05 Batuhan Koyuncu

Anomaly detection (AD) is a crucial machine learning task that aims to learn patterns from a set of normal training samples to identify abnormal samples in test data. Most existing AD studies assume that the training and test data are drawn…

Computer Vision and Pattern Recognition · Computer Science 2023-09-06 Tri Cao , Jiawen Zhu , Guansong Pang

Unsupervised anomaly detection (UAD) alleviates large labeling efforts by training exclusively on unlabeled in-distribution data and detecting outliers as anomalies. Generally, the assumption prevails that large training datasets allow the…

Computer Vision and Pattern Recognition · Computer Science 2024-10-29 Felix Meissen , Johannes Getzner , Alexander Ziller , Özgün Turgut , Georgios Kaissis , Martin J. Menten , Daniel Rueckert

Most unsupervised anomaly detection methods based on representations of normal samples to distinguish anomalies have recently made remarkable progress. However, existing methods only learn a single decision boundary for distinguishing the…

Computer Vision and Pattern Recognition · Computer Science 2024-09-10 Tianwu Lei , Silin Chen , Bohan Wang , Zhengkai Jiang , Ningmu Zou

The ability to detect unfamiliar or unexpected images is essential for safe deployment of computer vision systems. In the context of classification, the task of detecting images outside of a model's training domain is known as…

Computer Vision and Pattern Recognition · Computer Science 2024-04-03 Galadrielle Humblot-Renaux , Sergio Escalera , Thomas B. Moeslund

Recent advances in deep learning led to novel generative modeling techniques that achieve unprecedented quality in generated samples and performance in learning complex distributions in imaging data. These new models in medical image…

Computer Vision and Pattern Recognition · Computer Science 2018-06-15 Xiaoran Chen , Nick Pawlowski , Martin Rajchl , Ben Glocker , Ender Konukoglu

We propose a novel way to measure and understand convolutional neural networks by quantifying the amount of input signal they let in. To do this, an autoencoder (AE) was fine-tuned on gradients from a pre-trained classifier with fixed…

Computer Vision and Pattern Recognition · Computer Science 2018-03-23 Sebastian Palacio , Joachim Folz , Jörn Hees , Federico Raue , Damian Borth , Andreas Dengel

In this work, we train a network to simultaneously perform segmentation and pixel-wise Out-of-Distribution (OoD) detection, such that the segmentation of unknown regions of scenes can be rejected. This is made possible by leveraging an OoD…

Computer Vision and Pattern Recognition · Computer Science 2021-03-02 David Williams , Matthew Gadd , Daniele De Martini , Paul Newman

Out-of-distribution (OoD) detection is a natural downstream task for deep generative models, due to their ability to learn the input probability distribution. There are mainly two classes of approaches for OoD detection using deep…

Machine Learning · Computer Science 2019-07-11 Yujia Huang , Sihui Dai , Tan Nguyen , Richard G. Baraniuk , Anima Anandkumar

An autoencoder (AE) is a neural network that, using self-supervised training, learns a succinct parameterized representation, and a corresponding encoding and decoding process, for all instances in a given class. Here, we introduce the…

Machine Learning · Computer Science 2025-07-15 Assaf Marron , Smadar Szekely , Irun Cohen , David Harel

The phenomenon of double descent has challenged the traditional bias-variance trade-off in supervised learning but remains unexplored in unsupervised learning, with some studies arguing for its absence. In this study, we first demonstrate…

Machine Learning · Computer Science 2025-09-17 Kobi Rahimi , Yehonathan Refael , Tom Tirer , Ofir Lindenbaum

Out-of-distribution (OOD) detection recently has drawn attention due to its critical role in the safe deployment of modern neural network architectures in real-world applications. The OOD detectors aim to distinguish samples that lie…

Signal Processing · Electrical Eng. & Systems 2023-06-16 Sabri Mustafa Kahya , Muhammet Sami Yavuz , Eckehard Steinbach

Robustness in AI systems refers to their ability to maintain reliable and accurate performance under various conditions, including out-of-distribution (OOD) samples, adversarial attacks, and environmental changes. This is crucial in…

Artificial Intelligence · Computer Science 2025-10-15 Wissam Salhab , Darine Ameyed , Hamid Mcheick , Fehmi Jaafar

Unsupervised representation learning holds the promise of exploiting large amounts of unlabeled data to learn general representations. A promising technique for unsupervised learning is the framework of Variational Auto-encoders (VAEs).…

Computer Vision and Pattern Recognition · Computer Science 2020-04-09 Kamal Gupta , Saurabh Singh , Abhinav Shrivastava

A common belief in designing deep autoencoders (AEs), a type of unsupervised neural network, is that a bottleneck is required to prevent learning the identity function. Learning the identity function renders the AEs useless for anomaly…

Machine Learning · Computer Science 2022-02-28 Bang Xiang Yong , Alexandra Brintrup

Existing popular unsupervised embedding learning methods focus on enhancing the instance-level local discrimination of the given unlabeled images by exploring various negative data. However, the existed sample outliers which exhibit large…

Computer Vision and Pattern Recognition · Computer Science 2021-07-20 Jiahuan Zhou , Yansong Tang , Bing Su , Ying Wu

Anomalies are intuitively easy for human experts to understand, but they are hard to define mathematically. Therefore, in order to have performance guarantees in unsupervised anomaly detection, priors need to be assumed on what the…

Machine Learning · Statistics 2020-04-08 Tiago Pimentel , Marianne Monteiro , Adriano Veloso , Nivio Ziviani

Most of the existing methods for anomaly detection use only positive data to learn the data distribution, thus they usually need a pre-defined threshold at the detection stage to determine whether a test instance is an outlier.…

Machine Learning · Computer Science 2019-03-19 Kai Tian , Shuigeng Zhou , Jianping Fan , Jihong Guan

Does a Variational AutoEncoder (VAE) consistently encode typical samples generated from its decoder? This paper shows that the perhaps surprising answer to this question is `No'; a (nominally trained) VAE does not necessarily amortize…

Machine Learning · Computer Science 2020-12-08 A. Taylan Cemgil , Sumedh Ghaisas , Krishnamurthy Dvijotham , Sven Gowal , Pushmeet Kohli