Surfing the Network for Ranking by Multidamping

Abstract

PageRank is one of the most commonly used techniques for ranking nodes in a network. It is a special case of a family of link-based rankings, commonly referred to as functional rankings. Functional rankings are computed as power series of a stochastic matrix derived from the adjacency matrix of the graph. This general formulation of functional rankings enables their use in diverse applications, ranging from traditional search applications to identification of spam and outliers in networks. This paper presents a novel algorithmic (re)formulation of commonly used functional rankings, such as LinearRank, TotalRank and Generalized Hyperbolic Rank. These rankings can be approximated by finite series representations. We prove that polynomials of stochastic matrices can be expressed as products of Google matrices (matrices having the form used in Google's original PageRank formulation). Individual matrices in these products are parameterized by different damping factors. For this reason, we refer to our formulation as multidamping. We demonstrate that multidamping has a number of desirable characteristics: (i) for problems such as finding the highest ranked pages, multidamping admits extremely fast approximate solutions; (ii) multidamping provides an intuitive interpretation of existing functional rankings in terms of the surfing habits of model web users; (iii) multidamping provides a natural framework based on Monte Carlo type methods that have efficient parallel and distributed implementations. It also provides the basis for constructing new link-based rankings based on inhomogeneous products of Google matrices. We present algorithms for computing damping factors for existing functional rankings analytically and numerically. We validate various benefits of multidamping on a number of real datasets.