Community Discovery: Simple and Scalable Approaches

The increasing size and complexity of online social networks have brought distinct challenges to the task of community discovery. A community discovery algorithm needs to be efficient, not taking a prohibitive amount of time to finish. The algorithm should also be scalable, capable of handling large networks containing billions of edges or even more. Furthermore, a community discovery algorithm should be effective in that it produces community assignments of high quality. In this chapter, we present a selection of algorithms that follow simple design principles, and have proven highly effective and efficient according to extensive empirical evaluations. We start by discussing a generic approach of community discovery by combining multilevel graph contraction with core clustering algorithms. Next we describe the usage of network sampling in community discovery, where the goal is to reduce the number of nodes and/or edges while retaining the network’s underlying community structure. Finally, we review research efforts that leverage various parallel and distributed computing paradigms in community discovery, which can facilitate finding communities in tera- and peta-scale networks.