Item

Abstract

The approximate uniform sampling of graphs with a given degree sequence is a
well-known, extensively studied problem in theoretical computer science and has
significant applications, e.g., in the analysis of social networks. In this
work we study an extension of the problem, where degree intervals are specified
rather than a single degree sequence. We are interested in sampling and
counting graphs whose degree sequences satisfy the degree interval constraints.
A natural scenario where this problem arises is in hypothesis testing on social
networks that are only partially observed.
In this work, we provide the first fully polynomial almost uniform sampler
(FPAUS) as well as the first fully polynomial randomized approximation scheme
(FPRAS) for sampling and counting, respectively, graphs with near-regular
degree intervals, in which every node $i$ has a degree from an interval not too
far away from a given $d \in \N$. In order to design our FPAUS, we rely on
various state-of-the-art tools from Markov chain theory and combinatorics. In
particular, we provide the first non-trivial algorithmic application of a
breakthrough result of Liebenau and Wormald (2017) regarding an asymptotic
formula for the number of graphs with a given near-regular degree sequence.
Furthermore, we also make use of the recent breakthrough of Anari et al. (2019)
on sampling a base of a matroid under a strongly log-concave probability
distribution.
As a more direct approach, we also study a natural Markov chain recently
introduced by Rechner, Strowick and M\"uller-Hannemann (2018), based on three
simple local operations: Switches, hinge flips, and additions/deletions of a
single edge. We obtain the first theoretical results for this Markov chain by
showing it is rapidly mixing for the case of near-regular degree intervals of
size at most one.