Graph datasets with billions of edges, such as social and Web graphs, are prevalent. To be feasible, computation on such large graphs should scale linearly with graph size. All-distances sketches (ADSs) are emerging as a powerful tool for scalable computation of some basic properties of individual nodes or the whole graph.
ADSs were first proposed two decades ago (Cohen 1994) and more recent algorithms include ANF (Palmer, Gibbons, and Faloutsos 2002) and hyperANF (Boldi, Rosa, and Vigna 2011). A sketch of logarithmic size is computed for each node in the graph and the computation in total requires only a near linear number of edge relaxations. From the ADS of a node, we can estimate its neighborhood cardinalities (the number of nodes within some query distance) and closeness centrality. More generally we can estimate the distance distribution, effective diameter, similarities, and other parameters of the full graph. We make several contributions which facilitate a more effective use of ADSs for scalable analysis of massive graphs.
We provide, for the first time, a unified exposition of ADS algorithms and applications. We present the Historic Inverse Probability (HIP) estimators which are applied to the ADS of a node to estimate a large natural class of queries including neighborhood cardinalities and closeness centralities. We show that our HIP estimators have at most half the variance of previous neighborhood cardinality estimators and that this is essentially optimal. Moreover, HIP obtains a polynomial improvement for more general queries and the estimators are simple, flexible, unbiased, and elegant.
We apply HIP for approximate distinct counting on streams by comparing HIP and the original estimators applied to the HyperLogLog Min-Hash sketches (Flajolet et al. 2007). We demonstrate significant improvement in estimation quality for this state-of-the-art practical algorithm and also illustrate the ease of applying HIP.
Finally, we study the quality of ADS estimation of distance ranges, generalizing the near-linear time factor-2 approximation of the diameter.
|Published in||ACM SIGMOD/PODS 2014|