6 research outputs found
A Simple Deterministic Distributed MST Algorithm, with Near-Optimal Time and Message Complexities
Distributed minimum spanning tree (MST) problem is one of the most central
and fundamental problems in distributed graph algorithms. Garay et al.
\cite{GKP98,KP98} devised an algorithm with running time , where is the hop-diameter of the input -vertex -edge
graph, and with message complexity . Peleg and Rubinovich
\cite{PR99} showed that the running time of the algorithm of \cite{KP98} is
essentially tight, and asked if one can achieve near-optimal running time
**together with near-optimal message complexity**.
In a recent breakthrough, Pandurangan et al. \cite{PRS16} answered this
question in the affirmative, and devised a **randomized** algorithm with time
and message complexity . They asked if
such a simultaneous time- and message-optimality can be achieved by a
**deterministic** algorithm.
In this paper, building upon the work of \cite{PRS16}, we answer this
question in the affirmative, and devise a **deterministic** algorithm that
computes MST in time , using messages. The polylogarithmic factors in the time
and message complexities of our algorithm are significantly smaller than the
respective factors in the result of \cite{PRS16}. Also, our algorithm and its
analysis are very **simple** and self-contained, as opposed to rather
complicated previous sublinear-time algorithms \cite{GKP98,KP98,E04b,PRS16}
Minor Excluded Network Families Admit Fast Distributed Algorithms
Distributed network optimization algorithms, such as minimum spanning tree,
minimum cut, and shortest path, are an active research area in distributed
computing. This paper presents a fast distributed algorithm for such problems
in the CONGEST model, on networks that exclude a fixed minor.
On general graphs, many optimization problems, including the ones mentioned
above, require rounds of communication in the CONGEST
model, even if the network graph has a much smaller diameter. Naturally, the
next step in algorithm design is to design efficient algorithms which bypass
this lower bound on a restricted class of graphs. Currently, the only known
method of doing so uses the low-congestion shortcut framework of Ghaffari and
Haeupler [SODA'16]. Building off of their work, this paper proves that excluded
minor graphs admit high-quality shortcuts, leading to an round
algorithm for the aforementioned problems, where is the diameter of the
network graph. To work with excluded minor graph families, we utilize the Graph
Structure Theorem of Robertson and Seymour. To the best of our knowledge, this
is the first time the Graph Structure Theorem has been used for an algorithmic
result in the distributed setting.
Even though the proof is involved, merely showing the existence of good
shortcuts is sufficient to obtain simple, efficient distributed algorithms. In
particular, the shortcut framework can efficiently construct near-optimal
shortcuts and then use them to solve the optimization problems. This, combined
with the very general family of excluded minor graphs, which includes most
other important graph classes, makes this result of significant interest