Cover Time in Edge-Uniform Stochastically-Evolving Graphs

Lamprou, Ioannis ORCID: 0000-0001-5337-7336, Martin, Russell ORCID: 0000-0002-7043-503X and Spirakis, Paul ORCID: 0000-0001-5396-3749 (2017) Cover Time in Edge-Uniform Stochastically-Evolving Graphs. Lecture Notes in Computer Science, 10616. pp. 441-455.

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	Text 1702.05412v4.pdf - Author Accepted Manuscript Download (259kB)

Abstract

We define a general model of stochastically-evolving graphs, namely the \emph{Edge-Uniform Stochastically-Evolving Graphs}. In this model, each possible edge of an underlying general static graph evolves independently being either alive or dead at each discrete time step of evolution following a (Markovian) stochastic rule. The stochastic rule is identical for each possible edge and may depend on the past $k \ge 0$ observations of the edge's state. We examine two kinds of random walks for a single agent taking place in such a dynamic graph: (i) The \emph{Random Walk with a Delay} (\emph{RWD}), where at each step the agent chooses (uniformly at random) an incident possible edge, i.e., an incident edge in the underlying static graph, and then it waits till the edge becomes alive to traverse it. (ii) The more natural \emph{Random Walk on what is Available} (\emph{RWA}) where the agent only looks at alive incident edges at each time step and traverses one of them uniformly at random. Our study is on bounding the \emph{cover time}, i.e., the expected time until each node is visited at least once by the agent. For \emph{RWD}, we provide a first upper bound for the cases $k = 0, 1$ by correlating \emph{RWD} with a simple random walk on a static graph. Moreover, we present a modified electrical network theory capturing the $k = 0$ case. For \emph{RWA}, we derive some first bounds for the case $k = 0$, by reducing \emph{RWA} to an \emph{RWD}-equivalent walk with a modified delay. Further, we also provide a framework, which is shown to compute the exact value of the cover time for a general family of stochastically-evolving graphs in exponential time. Finally, we conduct experiments on the cover time of \emph{RWA} in Edge-Uniform graphs and compare the experimental findings with our theoretical bounds.

Item Type:	Article
Additional Information:	removed a few erroneous proofs, refreshed related work and experimental results
Uncontrolled Keywords:	cs.DC, cs.DC, cs.DM
Depositing User:	Symplectic Admin
Date Deposited:	23 Apr 2018 09:31
Last Modified:	19 Jan 2023 06:35
DOI:	10.1007/978-3-319-69084-1_33
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3020376