Engineering Multi-Level Overlay Graphs for Shortest-Path Queries

An overlay graph of a given graph G = (V, E) on a subset S subset of V is a graph with vertex set S that preserves some property of C. In particular, we consider variations of the multi-level overlay graph used in [21] to speed up shortest-path computations. In this work, we follow up and present general vertex selection criteria and strategies of applying these criteria to determine a subset S inducing an overlay graph. The main contribution is a systematic experimental study where we investigate the impact of selection criteria and strategies on multi-level overlay graphs and the resulting speed-up achieved for shortest-path queries. Depending on selection strategy and graph type, a centrality index criterion, a criterion based on planar separators, and vertex degree turned out to be good selection criteria.