Abstract
Graph structure learning (GSL), which aims to learn the adjacency matrix for
graph neural networks (GNNs), has shown great potential in boosting the
performance of GNNs. Most existing GSL works apply a joint learning framework
where the estimated adjacency matrix and GNN parameters are optimized for
downstream tasks. However, as GSL is essentially a link prediction task, whose
goal may largely differ from the goal of the downstream task. The inconsistency
of these two goals limits the GSL methods to learn the potential optimal graph
structure. Moreover, the joint learning framework suffers from scalability
issues in terms of time and space during the process of estimation and
optimization of the adjacency matrix. To mitigate these issues, we propose a
graph structure refinement (GSR) framework with a pretrain-finetune pipeline.
Specifically, The pre-training phase aims to comprehensively estimate the
underlying graph structure by a multi-view contrastive learning framework with
both intra- and inter-view link prediction tasks. Then, the graph structure is
refined by adding and removing edges according to the edge probabilities
estimated by the pre-trained model. Finally, the fine-tuning GNN is initialized
by the pre-trained model and optimized toward downstream tasks. With the
refined graph structure remaining static in the fine-tuning space, GSR avoids
estimating and optimizing graph structure in the fine-tuning phase which enjoys
great scalability and efficiency. Moreover, the fine-tuning GNN is boosted by
both migrating knowledge and refining graphs. Extensive experiments are
conducted to evaluate the effectiveness (best performance on six benchmark
datasets), efficiency, and scalability (13.8x faster using 32.8% GPU memory
compared to the best GSL baseline on Cora) of the proposed model.