1. A computer-implemented method of graph preprocessing, the method comprising: receiving as input a graph comprising a plurality of vertices and arcs; recursively processing, via the computer, a set of vertices of said graph that includes vertices with high vertex reaches using an iterative process which comprises: adding shortcut arcs to the graph; eliminating one or more vertices in the graph that are bypassed by an added shortcut arc; and storing a preprocessed graph comprising the added shortcut arcs.