Pseudo-labeling has proven to be a promising semi-supervised learning (SSL) paradigm. Existing pseudo-labeling methods commonly assume that the class distributions of training data are balanced. However, such an assumption is far from realistic scenarios and existing pseudo-labeling methods suffer from severe performance degeneration in the context of class-imbalance. In this work, we investigate pseudo-labeling under imbalanced semi-supervised setups. The core idea is to automatically assimilate the training bias arising from class-imbalance, using a bias adaptive classifier that equips the original linear classifier with a bias attractor. The bias attractor is designed to be a light-weight residual network for adapting to the training bias. Specifically, the bias attractor is learned through a bi-level learning framework such that the bias adaptive classifier is able to fit imbalanced training data, while the linear classifier can give unbiased label prediction for each class. We conduct extensive experiments under various imbalanced semi-supervised setups, and the results demonstrate that our method can be applicable to different pseudo-labeling models and superior to the prior arts.

本文提出了一种基于偏差自适应分类器的伪标签半监督学习方法，通过引入一个偏差吸引器来自动补偿类别不平衡带来的偏差，从而提高了伪标签方法在类别不平衡情况下的性能。实验证明，该方法优于现有的基准方法。

具有偏差自适应分类器的不平衡半监督学习