Enhancing Robust Fairness via Confusional Spectral Regularization
Gaojie Jin Sihao Wu Jiaxu Liu Tianjin Huang Ronghui Mu
Recent research has highlighted a critical issue known as ``robust fairness", where robust accuracy varies significantly across different classes, undermining the reliability of deep neural networks (DNNs). 
A common approach to address this has been to dynamically reweight classes during training, giving more weight to those with lower empirical robust performance. 
However, we find there is a divergence of class-wise robust performance between training set and testing set, which limits the effectiveness of these explicit reweighting methods, indicating the need for a principled alternative.
In this work, we derive a robust generalization bound for the worst-class robust error within the PAC-Bayesian framework, accounting for unknown data distributions. 
Our analysis shows that the worst-class robust error is influenced by two main factors: the spectral norm of the empirical robust confusion matrix and the information embedded in the model and training set. 
While the latter has been extensively studied, we propose a novel regularization technique targeting the spectral norm of the robust confusion matrix to improve worst-class robust accuracy and enhance robust fairness.
We validate our approach through comprehensive experiments on various datasets and models, demonstrating its effectiveness in enhancing robust fairness.
Adversarial robustness, Worst-class robust accuracy, Robust fairness, PAC-Bayes