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Sampling and Inference for Beta Neutral-to-the-Left Models of Sparse Networks
Proceedings of the 34th Conference on Uncertainty in Artificial Intelligence, PMLR R16:476-485, 2018.
Abstract
Empirical evidence suggests that heavy-tailed degree distributions occurring in many real net- works are well-approximated by power laws with exponents $\eta$ that may take values either less than and greater than two. Models based on various forms of exchangeability are able to capture power laws with $\eta$ < 2, and admit tractable inference algorithms; we draw on pre- vious results to show that $\eta$ > 2 cannot be gen- erated by the forms of exchangeability used in existing random graph models. Preferential at- tachment models generate power law exponents greater than two, but have been of limited use as statistical models due to the inherent difficulty of performing inference in non-exchangeable models. Motivated by this gap, we design and implement inference algorithms for a recently proposed class of models that generates $\eta$ of all possible values. We show that although they are not exchangeable, these models have prob- abilistic structure amenable to inference. Our methods make a large class of previously in- tractable models useful for statistical inference.