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Anomaly detection is to recognize samples that differ in some respect from the training observations. These samples which do not conform to the distribution of normal data are called outliers or anomalies. In real-world anomaly detection…

Computer Vision and Pattern Recognition · Computer Science 2022-07-05 Vahid Reza Khazaie , Anthony Wong , Yalda Mohsenzadeh

Reinforcement learning (RL) for large language model reasoning is frequently hindered by signal loss, a phenomenon where standard uniform sampling with small group sizes fails to uncover informative learning signals for difficult prompts.…

Machine Learning · Computer Science 2025-12-08 Wei Xiong , Chenlu Ye , Baohao Liao , Hanze Dong , Xinxing Xu , Christof Monz , Jiang Bian , Nan Jiang , Tong Zhang

Prototype-based reconstruction methods for unsupervised anomaly detection utilize a limited set of learnable prototypes which only aggregates insufficient normal information, resulting in undesirable reconstruction. However, increasing the…

Computer Vision and Pattern Recognition · Computer Science 2025-06-25 Ziqing Zhou , Yurui Pan , Lidong Wang , Wenbing Zhu , Mingmin Chi , Dong Wu , Bo Peng

In this study, a new Anomaly Detection (AD) approach for industrial and medical images is proposed. This method leverages the theoretical strengths of unsupervised learning and the data availability of both normal and abnormal classes.…

Computer Vision and Pattern Recognition · Computer Science 2024-01-24 Arnaud Bougaham , Valentin Delchevalerie , Mohammed El Adoui , Benoît Frénay

This study presents an adversarial method for anomaly detection in real-world applications, leveraging the power of generative adversarial neural networks (GANs) through cycle consistency in reconstruction error. Previous methods suffer…

Machine Learning · Computer Science 2024-05-01 Zahra Dehghanian , Saeed Saravani , Maryam Amirmazlaghani , Mohammad Rahmati

Anomaly detection is a ubiquitous and challenging task relevant across many disciplines. With the vital role communication networks play in our daily lives, the security of these networks is imperative for smooth functioning of society. To…

Cryptography and Security · Computer Science 2022-10-18 Gopikrishna Rathinavel , Nikhil Muralidhar , Timothy O'Shea , Naren Ramakrishnan

This paper investigates unsupervised anomaly detection in multivariate time-series data using reinforcement learning (RL) in the latent space of an autoencoder. A significant challenge is the limited availability of anomalous data, often…

Machine Learning · Computer Science 2025-02-11 Saba Sanami , Amir G. Aghdam

Time series anomaly detection presents various challenges due to the sequential and dynamic nature of time-dependent data. Traditional unsupervised methods frequently encounter difficulties in generalization, often overfitting to known…

Machine Learning · Statistics 2025-07-30 Aitor Sánchez-Ferrera , Borja Calvo , Jose A. Lozano

We propose the Autoencoding Binary Classifiers (ABC), a novel supervised anomaly detector based on the Autoencoder (AE). There are two main approaches in anomaly detection: supervised and unsupervised. The supervised approach accurately…

Machine Learning · Statistics 2019-03-27 Yuki Yamanaka , Tomoharu Iwata , Hiroshi Takahashi , Masanori Yamada , Sekitoshi Kanai

We propose a hybrid approach to temporal anomaly detection in access data of users to databases --- or more generally, any kind of subject-object co-occurrence data. We consider a high-dimensional setting that also requires fast computation…

Cryptography and Security · Computer Science 2019-08-13 Eyal Gutflaish , Aryeh Kontorovich , Sivan Sabato , Ofer Biller , Oded Sofer

Anomaly detection on tabular data is commonly studied under three supervision regimes, including one-class settings that assume access to anomaly-free training samples, fully unsupervised settings with unlabeled and potentially contaminated…

Machine Learning · Computer Science 2026-03-23 Jack Yi Wei , Narges Armanfard

Deep anomaly detection models using a supervised mode of learning usually work under a closed set assumption and suffer from overfitting to previously seen rare anomalies at training, which hinders their applicability in a real scenario. In…

Image and Video Processing · Electrical Eng. & Systems 2020-10-26 Behzad Bozorgtabar , Dwarikanath Mahapatra , Guillaume Vray , Jean-Philippe Thiran

Unsupervised learning of anomaly detection in high-dimensional data, such as images, is a challenging problem recently subject to intense research. Through careful modelling of the data distribution of normal samples, it is possible to…

Computer Vision and Pattern Recognition · Computer Science 2019-11-21 Amanda Berg , Jörgen Ahlberg , Michael Felsberg

Anomaly detection is a significant and hence well-studied problem. However, developing effective anomaly detection methods for complex and high-dimensional data remains a challenge. As Generative Adversarial Networks (GANs) are able to…

Machine Learning · Computer Science 2018-12-07 Houssam Zenati , Manon Romain , Chuan Sheng Foo , Bruno Lecouat , Vijay Ramaseshan Chandrasekhar

Well-known for its simplicity and effectiveness in classification, AdaBoost, however, suffers from overfitting when class-conditional distributions have significant overlap. Moreover, it is very sensitive to noise that appears in the…

Machine Learning · Statistics 2018-06-22 Zhi Xiao , Zhe Luo , Bo Zhong , Xin Dang

Recent studies give more attention to the anomaly detection (AD) methods that can leverage a handful of labeled anomalies along with abundant unlabeled data. These existing anomaly-informed AD methods rely on manually predefined score…

Machine Learning · Computer Science 2023-06-27 Minqi Jiang , Songqiao Han , Hailiang Huang

Anomaly detection (AD) is a machine learning task that identifies anomalies by learning patterns from normal training data. In many real-world scenarios, anomalies vary in severity, from minor anomalies with little risk to severe…

Machine Learning · Computer Science 2024-11-25 Tri Cao , Minh-Huy Trinh , Ailin Deng , Quoc-Nam Nguyen , Khoa Duong , Ngai-Man Cheung , Bryan Hooi

Anomaly detection has recently seen great progress in the field of visual inspection. More specifically, the use of classical outlier detection techniques on features extracted by deep pre-trained neural networks have been shown to deliver…

Computer Vision and Pattern Recognition · Computer Science 2022-02-28 Antoine Cordier , Benjamin Missaoui , Pierre Gutierrez

Several techniques for multivariate time series anomaly detection have been proposed recently, but a systematic comparison on a common set of datasets and metrics is lacking. This paper presents a systematic and comprehensive evaluation of…

Machine Learning · Computer Science 2021-09-24 Astha Garg , Wenyu Zhang , Jules Samaran , Savitha Ramasamy , Chuan-Sheng Foo

Universal anomaly detection still remains a challenging problem in machine learning and medical image analysis. It is possible to learn an expected distribution from a single class of normative samples, e.g., through epistemic uncertainty…

Computer Vision and Pattern Recognition · Computer Science 2023-10-03 Johanna P. Müller , Matthew Baugh , Jeremy Tan , Mischa Dombrowski , Bernhard Kainz