Supplementary Material : Large-scale community structurein social and information networks

• We use several classes of graph partitioning algorithms to p robe the networks for sets of nodes that could plausibly be interpreted as communities. These algor ithms, including flow-based methods, spectral methods, and hierarchical methods, have compleme ntary strengths and weaknesses that are well understood both in theory and in practice. For examp le, flow-based methods are known to have difficulties with expanders ( 42, 43), and flow-based post-processing of other methods are known in practice to yield cuts with extremely good conducta n e values ( 39, 41). On the other hand, spectral methods are known to have difficulties when th y confuse long paths with deep

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