VCSR: Mutable CSR Graph Format Using Vertex-Centric Packed Memory Array

The compressed sparse row (CSR) is a widely used graph storage format due to its compact memory layout and high performance on graph analytic tasks. However, the compact design also limits itself from supporting many graph applications that operate on dynamic or temporal graphs as updates on these graph will need to rebuild the entire CSR structure, leading to high costs. Extending CSR to support efficient graph mutations without losing its high performance on graph analysis then becomes critical to these applications. Existing mutable CSR extensions leverage packed memory array (PMA) to store edge list to enable graph mutations. But, such a naive way has fundamental limitations in handling imbalanced graphs, which many real-world graphs belong to. To address such issues, we propose VCSR, a new mutable CSR storage format that leverages the packed memory array (PMA) via a new vertex-centric strategy to efficiently support temporal graphs. Our evaluation results show that compared with the state-of-the-art mutable CSR extensions, VCSR can achieve 1.41x-3.81x better performance in graph insertions and 1.22x-2.05x better performance in running typical graph analytic algorithms. In addition, VCSR can achieve similar performance as the original immutable CSR in running graph analytic tasks, making it a promising storage format for temporal graphs.