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Metric learning seeks perceptual embeddings where visually similar instances are close and dissimilar instances are apart, but learned representations can be sub-optimal when the distribution of intra-class samples is diverse and distinct…

Machine Learning · Computer Science 2021-08-30 Elad Levi , Tete Xiao , Xiaolong Wang , Trevor Darrell

Contrastive learning is an efficient approach to self-supervised representation learning. Although recent studies have made progress in the theoretical understanding of contrastive learning, the investigation of how to characterize the…

Machine Learning · Computer Science 2023-08-21 Hiroki Waida , Yuichiro Wada , Léo Andéol , Takumi Nakagawa , Yuhui Zhang , Takafumi Kanamori

In this study, we systematically investigate the impact of class imbalance on classification performance of convolutional neural networks (CNNs) and compare frequently used methods to address the issue. Class imbalance is a common problem…

Computer Vision and Pattern Recognition · Computer Science 2018-10-16 Mateusz Buda , Atsuto Maki , Maciej A. Mazurowski

Learning generalizable self-supervised graph representations for downstream tasks is challenging. To this end, Contrastive Learning (CL) has emerged as a leading approach. The embeddings of CL are arranged on a hypersphere where similarity…

Machine Learning · Computer Science 2025-02-25 Yifei Zhang , Hao Zhu , Menglin Yang , Jiahong Liu , Rex Ying , Irwin King , Piotr Koniusz

While Contrastive Learning (CL) has revolutionized self-supervised representation learning, its latent representations remain highly entangled and opaque, limiting their interpretability in safety-critical applications. We identify that a…

Computer Vision and Pattern Recognition · Computer Science 2026-05-28 Peng Cui , Jiahao Zhang , Lijie Hu

Contrastive learning has emerged as a powerful method in deep learning, excelling at learning effective representations through contrasting samples from different distributions. However, neural collapse, where embeddings converge into a…

Machine Learning · Computer Science 2024-10-08 Huanran Li , Manh Nguyen , Daniel Pimentel-Alarcón

This paper studies the problem of class-imbalanced graph classification, which aims at effectively classifying the graph categories in scenarios with imbalanced class distributions. While graph neural networks (GNNs) have achieved…

Machine Learning · Computer Science 2024-12-31 Wei Ju , Zhengyang Mao , Siyu Yi , Yifang Qin , Yiyang Gu , Zhiping Xiao , Jianhao Shen , Ziyue Qiao , Ming Zhang

Contrastive learning (CL) aims to learn useful representation without relying on expert annotations in the context of medical image segmentation. Existing approaches mainly contrast a single positive vector (i.e., an augmentation of the…

Computer Vision and Pattern Recognition · Computer Science 2022-03-08 Chenyu You , Ruihan Zhao , Lawrence Staib , James S. Duncan

This work investigates the phenomenon of Neural Collapse (NC) in multi-label classification, extending its conceptual framework from multi-class learning to general correlated and imbalanced multi-label settings. Although recent studies…

Machine Learning · Computer Science 2026-05-05 Xiaoxuan Ma , Yixuan Yang , Song Li , Xiangyun Hui

Contrastive representation learning has been outstandingly successful in practice. In this work, we identify two key properties related to the contrastive loss: (1) alignment (closeness) of features from positive pairs, and (2) uniformity…

Machine Learning · Computer Science 2022-08-17 Tongzhou Wang , Phillip Isola

Class imbalance is a common problem in the case of real-world object detection and classification tasks. Data of some classes is abundant making them an over-represented majority, and data of other classes is scarce, making them an…

Computer Vision and Pattern Recognition · Computer Science 2017-03-24 Salman H. Khan , Munawar Hayat , Mohammed Bennamoun , Ferdous Sohel , Roberto Togneri

Neural collapse provides an elegant mathematical characterization of learned last layer representations (a.k.a. features) and classifier weights in deep classification models. Such results not only provide insights but also motivate new…

Machine Learning · Computer Science 2023-10-30 Jiachen Jiang , Jinxin Zhou , Peng Wang , Qing Qu , Dustin Mixon , Chong You , Zhihui Zhu

Despite the success of contrastive learning (CL) in vision and language, its theoretical foundations and mechanisms for building representations remain poorly understood. In this work, we build connections between noise contrastive…

Machine Learning · Computer Science 2025-02-28 Zihao Chen , Chi-Heng Lin , Ran Liu , Jingyun Xiao , Eva L Dyer

Recent studies on Neural Collapse (NC) reveal that, under class-balanced conditions, the class feature means and classifier weights spontaneously align into a simplex equiangular tight frame (ETF). In long-tailed regimes, however, severe…

Machine Learning · Computer Science 2025-12-10 Jinping Wang , Zhiqiang Gao , Zhiwu Xie

Supervised classification has a theoretical optimum, Neural Collapse (NC), yet neither of its two dominant paradigms reaches it in practice. Cross entropy (CE) leaves radial degrees of freedom unconstrained and converges to a degenerate…

Machine Learning · Computer Science 2026-05-22 Panagiotis Koromilas , Theodoros Giannakopoulos , Mihalis A. Nicolaou , Yannis Panagakis

Supervised contrastive learning (SupCL) has emerged as a prominent approach in representation learning, leveraging both supervised and self-supervised losses. However, achieving an optimal balance between these losses is challenging;…

Machine Learning · Computer Science 2025-03-12 Chungpa Lee , Jeongheon Oh , Kibok Lee , Jy-yong Sohn

Modern deep neural networks for classification usually jointly learn a backbone for representation and a linear classifier to output the logit of each class. A recent study has shown a phenomenon called neural collapse that the within-class…

Machine Learning · Computer Science 2022-10-13 Yibo Yang , Shixiang Chen , Xiangtai Li , Liang Xie , Zhouchen Lin , Dacheng Tao

Data for face analysis often exhibit highly-skewed class distribution, i.e., most data belong to a few majority classes, while the minority classes only contain a scarce amount of instances. To mitigate this issue, contemporary deep…

Computer Vision and Pattern Recognition · Computer Science 2019-05-01 Chen Huang , Yining Li , Chen Change Loy , Xiaoou Tang

We propose Graph Contrastive Learning (GraphCL), a general framework for learning node representations in a self supervised manner. GraphCL learns node embeddings by maximizing the similarity between the representations of two randomly…

Machine Learning · Computer Science 2020-07-17 Hakim Hafidi , Mounir Ghogho , Philippe Ciblat , Ananthram Swami

Loss reweighting is a widely used strategy for long-tailed classification, but existing reweighting strategies often rely on heuristics and rarely define a well-specified target. Inspired by Neural Collapse (NC), the ideal simplex…

Machine Learning · Computer Science 2026-05-12 Jinping Wang , Zixin Tong , Zhiwu Xie , Zhiqiang Gao