Graph Neural Networks (GNNs) extend basic Neural Networks (NNs) by using graph structures based on the relational inductive bias (homophily assumption). While GNNs have been commonly believed to outperform NNs in real-world tasks, recent work has identified a non-trivial set of datasets where their performance compared to NNs is not satisfactory. Heterophily has been considered the main cause of this empirical observation and numerous works have been put forward to address it. In this paper, we first revisit the widely used homophily metrics and point out that their consideration of only graph-label consistency is a shortcoming. Then, we study heterophily from the perspective of post-aggregation node similarity and define new homophily metrics, which are potentially advantageous compared to existing ones. Based on this investigation, we prove that some harmful cases of heterophily can be effectively addressed by local diversification operation. Then, we propose the Adaptive Channel Mixing (ACM), a framework to adaptively exploit aggregation, diversification and identity channels node-wisely to extract richer localized information for diverse node heterophily situations. ACM is more powerful than the commonly used uni-channel framework for node classification tasks on heterophilic graphs and is easy to be implemented in baseline GNN layers. When evaluated on 10 benchmark node classification tasks, ACM-augmented baselines consistently achieve significant performance gain, exceeding state-of-the-art GNNs on most tasks without incurring significant computational burden.

本文通过重新评估广泛使用的同质性度量，并从后集成节点相似性的角度研究了异质性。提出了一种新的度量方法，并证明了local diversification operation可以有效解决一些有害的异质性情况，然后提出了Adaptive Channel Mixing（ACM）框架来自适应地利用聚合，多样性和标识通道，从而从多样化的节点异质性情况中提取更丰富的局部信息。经过10项基准节点分类任务的评估，ACM-augmented基线始终实现了显着的性能提升，超过大多数任务上的最新GNN，而不会带来显着的计算负担。

重新审视异质性对图神经网络的影响