Scalable betweenness centrality on multi-GPU systems

Betweenness Centrality (BC) is steadily growing in popularity as a metrics of the influence of a vertex in a graph. The BC score of a vertex is proportional to the number of all-pairs-shortest-paths passing through it. However, complete and exact BC computation for a large-scale graph is an extraordinary challenge that requires high performance computing techniques to provide results in a reasonable amount of time. Our approach combines bi-dimensional (2-D) decomposition of the graph and multi-level parallelism together with a suitable data-Thread mapping that overcomes most of the difficulties caused by the irregularity of the computation on GPUs. In order to reduce time and space requirements of BC computation, a heuristics based on 1-degree reduction technique is developed as well. Experimental results on synthetic and real-world graphs show that the proposed techniques are well suited to compute BC scores in graphs which are too large to fit in the memory of a single computational node.