Graph Neural Networks (GNNs) have demonstrated significant success in graph learning and are widely adopted across various critical domains. However, the irregular connectivity between vertices leads to inefficient neighbor aggregation, resulting in substantial irregular and coarse-grained DRAM accesses. This lack of data locality presents significant challenges for execution platforms, ultimately degrading performance. While previous accelerator designs have leveraged on-chip memory and data access scheduling strategies to address this issue, they still inevitably access features at irregular addresses from DRAM. In this work, we propose LiGNN, a hardware-based solution that enhances locality and applies dropout to aggregation to accelerate GNN training. Unlike algorithmic dropout approaches that primarily focus on improving accuracy and neglects hardware costs, LiGNN is specifically designed to drop nodes' features with data locality awareness, directly targeting the reduction of irregular DRAM accesses, meanwhile maintaining accuracy. LiGNN introduces locality-aware ordering and a DRAM row integrity policy, enabling configurable burst and row-granularity dropout at the DRAM level. This approach improves data locality and ensures more efficient DRAM access. Compared to state-of-the-art methods, under classic 0.5 droprate, LiGNN achieves a 1.62~2.2× speedup, reduces DRAM accesses by 44~50% and DRAM row activation by 41~82%, all without losing accuracy.

Limited by the memory capacity and compute power, singe-node graph convolutional neural network (GCN) accelerators cannot complete the execution of GCNs within a reasonable amount of time, due to the explosive size of graphs nowadays. Thus, large-scale GCNs call for a multi-node acceleration system (MultiAccSys) like TPU-Pod for large-scale neural networks. In this work, we aim to scale up single-node GCN accelerators to accelerate GCNs on large-scale graphs. We first identify the communication pattern and challenges of multi-node acceleration for GCNs on large-scale graphs. We observe that (1) coarse-grained communication patterns exist in the execution of GCNs in MultiAccSys, which introduces massive amount of redundant network transmissions and off-chip memory accesses; (2) overall, the acceleration of GCNs in MultiAccSys is bandwidth-bound and latency-tolerant. Guided by these two observations, we then propose MultiGCN, the first MultiAccSys for large-scale GCNs that trades network latency for network bandwidth. Specifically, by leveraging the network latency tolerance, wefirstpropose a topology-aware multicast mechanism with a oneputpermulticastmessage-passing model to reduce transmissions and alleviate network bandwidth requirements.Second, we introduce a scatter-based round execution mechanism which cooperates with the multicast mechanism and reduces redundant off-chip memory accesses. Compared to the baseline MultiAccSys, MultiGCN achieves 4$\sim 12\times$speedup using only 28%$\sim$68% energy, while reducing 32% transmissions and 73% off-chip memory accesses on average. It not only achieves 2.5$\sim 8\times$speedup over the state-of-the-art multi-GPU solution, but also scales to large-scale graphs as opposed to single-node GCN accelerators.