Robustness of Graph Classification: failure modes, causes, and noise-resistant loss in Graph Neural Networks

Graph Neural Networks (GNNs) are powerful at solving graph classification tasks, yet applied problems often contain noisy labels. In this work, we study GNN robustness to label noise, demonstrate GNN failure modes when models struggle to generalise on low-order graphs, low label coverage, or when a model is over-parameterized. We establish both empirical and theoretical links between GNN robustness and the reduction of the total Dirichlet Energy of learned node representations, which encapsulates the hypothesized GNN smoothness inductive bias. Finally, we introduce two training strategies to enhance GNN robustness: (1) by incorporating a novel inductive bias in the weight matrices through the removal of negative eigenvalues, connected to Dirichlet Energy minimization; (2) by extending to GNNs a loss penalty that promotes learned smoothness. Importantly, neither approach negatively impacts performance in noise-free settings, supporting our hypothesis that the source of GNNs robustness is their smoothness inductive bias.

Combining Distance to Class Centroids and Outlier Discounting for Improved Learning with Noisy Labels

In this paper, we propose a new approach for addressing the challenge of training machine learning models in the presence of noisy labels. By combining a clever usage of distance to class centroids in the items' latent space with a discounting strategy to reduce the importance of samples far away from all the class centroids (i.e., outliers), our method effectively addresses the issue of noisy labels. Our approach is based on the idea that samples farther away from their respective class centroid in the early stages of training are more likely to be noisy. We demonstrate the effectiveness of our method through extensive experiments on several popular benchmark datasets. Our results show that our approach outperforms the state-of-the-art in this area, achieving significant improvements in classification accuracy when the dataset contains noisy labels.