Planting Trees for scalable and efficient Canonical Hub Labeling

Point-to-Point Shortest Distance (PPSD) query is a crucial primitive in graph database applications. Hub labeling algorithms compute a labeling that converts a PPSD query into a list intersection problem (over a pre-computed indexing) enabling swift query response. However, constructing hub labeling is computationally challenging. Even state-of-the-art parallel algorithms based on Pruned Landmark Labeling (PLL) [3], are plagued by large label size, violation of given network hierarchy, poor scalability and inability to process large graphs. In this paper, we develop novel parallel shared-memory and distributed-memory algorithms for constructing the Canonical Hub Labeling (CHL) that is minimal in size for a given network hierarchy. To the best of our knowledge, none of the existing parallel algorithms guarantee canonical labeling. Our key contribution, the PLaNT algorithm, scales well beyond the limits of current practice by completely avoiding inter-node communication. PLaNT also enables the design of a collaborative label partitioning scheme across multiple nodes for completely in-memory processing of massive graphs whose labels cannot fit on a single machine. Compared to the sequential PLL, we empirically demonstrate upto 47.4x speedup on a 72 thread shared-memory platform. On a 64-node cluster, PLaNT achieves an average 42x speedup over single node execution. Finally, we show how our approach demonstrates superior scalability - we can process 14x larger graphs (in terms of label size) and construct hub labeling orders of magnitude faster compared to state-of-the-art distributed paraPLL algorithm.