Fast Unsupervised Graph Embedding via Graph Zoom Learning.

Unsupervised graph representation learning, i.e., learning node or graph embeddings from graph data in an unsupervised manner, has become an important problem when we study graph data. With the development of self-supervised learning, researchers have designed graph-level self-supervised learning paradigms and learn embeddings under these paradigms. The learned embeddings can serve as a fine initial solution to downstream tasks such as node classification or graph classification. In this paper, we propose a fast unsupervised graph embedding method, which follows the way of self-supervised learning. This method performs representation learning on the graph under a novel concept called Graph Zoom Learning (abbr. GZL), which is orthogonal to the existing concepts of unsupervised graph embedding, such as random walk and contrastive learning. Two crucial components, graph zoom-out and point-to-point contrast, help GZL reduce the overall training time cost. Specifically, on the one hand, a lightweight miniature graph is generated from the raw graph by graph zoom-out and the learning on the miniature graph is more efficient than the learning on the raw graph; on the other hand, we design the miniature-scale learning on the miniature graph and introduce community structure into this learning pattern, which contributes to the final point-to-point contrast. Since point-to-point contrast is independent of negatives, it makes the whole training more efficient. We conduct extensive experiments to verify the advantage of GZL on representation learning. On two downstream tasks of node classification and graph classification, GZL outperforms the state-of-the-art unsupervised graph embedding methods. Particularly, on the largest experimental graph dataset (ogbn-arxiv) with 169k nodes and 1.1m edges, GZL outperforms the runner-up by 3.3% relative accuracy and achieves up to 22.6x speedup over it.