A Closer Look at Distribution Shifts and Out-of-Distribution Generalization on Graphs

Distribution shifts, in which the training distribution differs from the testing distribution, can significantly degrade the performance of Graph Neural Networks (GNNs). We curate GDS, a benchmark of eight datasets reflecting a diverse range of distribution shifts across graphs. We observe that: (1) most domain generalization algorithms fail to work when applied to domain shifts on graphs; and (2) combinations of powerful GNN models and augmentation techniques usually achieve the best out-of-distribution performance. These emphasize the need for domain generalization algorithms tailored for graphs and further graph augmentation techniques that enhance the robustness of predictors.