用针对性混合提升图像半监督模型校准度,更准更可信。
CalibrateMix: Guided-Mixup Calibration of Image Semi-Supervised Models
- 按难易区分样本,对易难样本分别做有目的的混合
- 在多个数据集上降低预期校准误差(ECE),准确率更高
- 适合追求高置信度预测可靠性的半监督学习应用
半监督学习(SSL)通过有效利用标注和未标注数据,在图像分类任务中表现优异。然而,现有方法常因模型预测过于自信而校准性差,无法真实反映预测概率。最近研究表明,在监督学习中使用随机混合训练样本(mixup)能改善校准。但在半监督设置下,伪标签存在过度自信与不可靠问题,直接混合适用受限。本文提出 CalibrateMix,一种基于目标混合的方法,通过分析标注与未标注样本的训练动态,识别出“易学”和“难学”样本,并对这两类样本分别进行有针对性的 mixup 混合。在多个基准图像数据集上的实验表明,该方法显著降低了预期校准误差(ECE),同时保持或提升了分类准确率。
原文摘要 · Abstract (English)
Semi-supervised learning (SSL) has demonstrated high performance in image classification tasks by effectively utilizing both labeled and unlabeled data. However, existing SSL methods often suffer from poor calibration, with models yielding overconfident predictions that misrepresent actual prediction likelihoods. Recently, neural networks trained with {\tt mixup} that linearly interpolates random examples from the training set have shown better calibration in supervised settings. However, calibration of neural models remains under-explored in semi-supervised settings. Although effective in supervised model calibration, random mixup of pseudolabels in SSL presents challenges due to the overconfidence and unreliability of pseudolabels. In this work, we introduce CalibrateMix, a targeted mixup-based approach that aims to improve the calibration of SSL models while maintaining or even improving their classification accuracy. Our method leverages training dynamics of labeled and unlabeled samples to identify ``easy-to-learn'' and ``hard-to-learn'' samples, which in turn are utilized in a targeted mixup of easy and hard samples. Experimental results across several benchmark image datasets show that our method achieves lower expected calibration error (ECE) and superior accuracy compared to existing SSL approaches.
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