Data are maintained in a distributed computing system that describe a directed graph representing relationships among items. The directed graph has a plurality of vertices representing the items and has edges with values representing distances between the items connected by the vertices. A multiple reference point algorithm is executed for a plurality of the vertices in the directed graph in parallel for a series of synchronized iterations to determine shortest distances between the vertices and the source vertex. After executing the algorithm on the vertices, value pairs associated with the vertices are aggregated. The aggregated value pairs indicate shortest distances from the respective vertices to the source vertex. The aggregated value pairs are outputted.