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Deep classifier neural networks enter the terminal phase of training (TPT) when training error reaches zero and tend to exhibit intriguing Neural Collapse (NC) properties. Neural collapse essentially represents a state at which the…

Machine Learning · Computer Science 2023-04-12 Vignesh Kothapalli

Federated Long-Tailed Learning (Fed-LT), a paradigm wherein data collected from decentralized local clients manifests a globally prevalent long-tailed distribution, has garnered considerable attention in recent times. In the context of…

Machine Learning · Computer Science 2024-03-11 Zikai Xiao , Zihan Chen , Liyinglan Liu , Yang Feng , Jian Wu , Wanlu Liu , Joey Tianyi Zhou , Howard Hao Yang , Zuozhu Liu

When training deep neural networks for classification tasks, an intriguing empirical phenomenon has been widely observed in the last-layer classifiers and features, where (i) the class means and the last-layer classifiers all collapse to…

Machine Learning · Computer Science 2022-03-15 Jinxin Zhou , Xiao Li , Tianyu Ding , Chong You , Qing Qu , Zhihui Zhu

Object frequency in the real world often follows a power law, leading to a mismatch between datasets with long-tailed class distributions seen by a machine learning model and our expectation of the model to perform well on all classes. We…

Computer Vision and Pattern Recognition · Computer Science 2020-03-25 Muhammad Abdullah Jamal , Matthew Brown , Ming-Hsuan Yang , Liqiang Wang , Boqing Gong

Neural collapse ($\mathcal{NC}$) is a phenomenon observed in classification tasks where top-layer representations collapse into their class means, which become equinorm, equiangular and aligned with the classifiers. These behaviours --…

Machine Learning · Computer Science 2024-11-27 Robert Wu , Vardan Papyan

Balancing performance trade-off on long-tail (LT) data distributions remains a long-standing challenge. In this paper, we posit that this dilemma stems from a phenomenon called "tail performance degradation" (the model tends to severely…

Computer Vision and Pattern Recognition · Computer Science 2026-03-24 Shenghan Chen , Yiming Liu , Yanzhen Wang , Yujia Wang , Xiankai Lu

The long-tail distribution of the visual world poses great challenges for deep learning based classification models on how to handle the class imbalance problem. Existing solutions usually involve class-balancing strategies, e.g., by loss…

Computer Vision and Pattern Recognition · Computer Science 2020-02-20 Bingyi Kang , Saining Xie , Marcus Rohrbach , Zhicheng Yan , Albert Gordo , Jiashi Feng , Yannis Kalantidis

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

Deep learning enables impressive performance in image recognition using large-scale artificially-balanced datasets. However, real-world datasets exhibit highly class-imbalanced distributions, yielding two main challenges: relative imbalance…

Computer Vision and Pattern Recognition · Computer Science 2020-10-20 Saurabh Sharma , Ning Yu , Mario Fritz , Bernt Schiele

Neural collapse (NC) is a simple and symmetric phenomenon for deep neural networks (DNNs) at the terminal phase of training, where the last-layer features collapse to their class means and form a simplex equiangular tight frame aligning…

Machine Learning · Computer Science 2024-05-03 Sicong Wang , Kuo Gai , Shihua Zhang

Existing long-tailed classification (LT) methods only focus on tackling the class-wise imbalance that head classes have more samples than tail classes, but overlook the attribute-wise imbalance. In fact, even if the class is balanced,…

Computer Vision and Pattern Recognition · Computer Science 2025-10-14 Kaihua Tang , Mingyuan Tao , Jiaxin Qi , Zhenguang Liu , Hanwang Zhang

The conventional detectors tend to make imbalanced classification and suffer performance drop, when the distribution of the training data is severely skewed. In this paper, we propose to use the mean classification score to indicate the…

Computer Vision and Pattern Recognition · Computer Science 2021-08-19 Chengjian Feng , Yujie Zhong , Weilin Huang

Incremental learning often encounter challenges such as overfitting to new data and catastrophic forgetting of old data. Existing methods can effectively extend the model for new tasks while freezing the parameters of the old model, but…

Computer Vision and Pattern Recognition · Computer Science 2025-12-29 Chuangxin Zhang , Guangfeng Lin , Enhui Zhao , Kaiyang Liao , Yajun Chen

The recently discovered Neural Collapse (NC) phenomenon occurs pervasively in today's deep net training paradigm of driving cross-entropy (CE) loss towards zero. During NC, last-layer features collapse to their class-means, both classifiers…

Machine Learning · Computer Science 2022-05-11 X. Y. Han , Vardan Papyan , David L. Donoho

In recent years, deep neural networks (DNNs) have demonstrated state-of-the-art performance across various domains. However, despite their success, they often face calibration issues, particularly in safety-critical applications such as…

Machine Learning · Computer Science 2025-04-15 Jiani Ni , He Zhao , Jintong Gao , Dandan Guo , Hongyuan Zha

Adversarial training is effective on balanced datasets, but its robustness degrades under longtailed class distributions, where tail classes suffer high robust error and unstable decision boundaries. We propose Manifold-Constrained…

Machine Learning · Computer Science 2026-05-05 Guanmeng Xian , Ning Yang , Philip S. Yu

Prompt learning has emerged as an efficient alternative to fine-tuning pre-trained vision-language models (VLMs). Despite its promise, current methods still struggle to maintain tail-class discriminability when adapting to class-imbalanced…

Computer Vision and Pattern Recognition · Computer Science 2026-05-13 Boyang Guo , Liang Li , Lin Peng , Yuhan Gao , Xichun Sheng , Chenggang Yan

Real-world data is often unbalanced and long-tailed, but deep models struggle to recognize rare classes in the presence of frequent classes. To address unbalanced data, most studies try balancing the data, the loss, or the classifier to…

Machine Learning · Computer Science 2021-11-02 Dvir Samuel , Gal Chechik

Neural collapse, a newly identified characteristic, describes a property of solutions during model training. In this paper, we explore neural collapse in the context of imbalanced data. We consider the $L$-extended unconstrained feature…

Machine Learning · Computer Science 2024-11-27 Haixia Liu

Neural collapse (NC) is a phenomenon that emerges at the terminal phase of the training (TPT) of deep neural networks (DNNs). The features of the data in the same class collapse to their respective sample means and the sample means exhibit…

Machine Learning · Statistics 2024-09-09 Wanli Hong , Shuyang Ling