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 re-weighting, data re-sampling, or transfer learning from head- to tail-classes, but most of them adhere to the scheme of jointly learning representations and classifiers. In this work, we decouple the learning procedure into representation learning and classification, and systematically explore how different balancing strategies affect them for long-tailed recognition. The findings are surprising: (1) data imbalance might not be an issue in learning high-quality representations; (2) with representations learned with the simplest instance-balanced (natural) sampling, it is also possible to achieve strong long-tailed recognition ability at little cost by adjusting only the classifier. We conduct extensive experiments and set new state-of-the-art performance on common long-tailed benchmarks like ImageNet-LT, Places-LT and iNaturalist, showing that it is possible to outperform carefully designed losses, sampling strategies, even complex modules with memory, by using a straightforward approach that decouples representation and classification.

本研究中，我们解耦学习过程，系统地探索不同平衡策略如何影响长尾识别的表示学习和分类器。我们的发现表明，数据不平衡在学习高质量表示方面可能不是问题，在使用最简单的实例平衡抽样进行学习表示的情况下，只需调整分类器就能实现强大的长尾识别能力，甚至可以胜过精心设计的损失、采样策略以及使用记忆组件的复杂模块。

长尾识别的表示与分类器解耦