2011 | OriginalPaper | Buchkapitel
A (1 + ln 2)-Approximation Algorithm for Minimum-Cost 2-Edge-Connectivity Augmentation of Trees with Constant Radius
verfasst von : Nachshon Cohen, Zeev Nutov
Erschienen in: Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques
Verlag: Springer Berlin Heidelberg
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We consider the
Tree Augmentation
problem: given a graph
G
= (
V
,
E
) with edge-costs and a tree
T
on
V
disjoint to
E
, find a minimum-cost edge-subset
F
⊆
E
such that
T
∪
F
is 2-edge-connected.
Tree Augmentation
is equivalent to the problem of finding a minimum-cost edge-cover
F
⊆
E
of a laminar set-family. The best known approximation ratio for
Tree Augmentation
is 2, even for trees of radius 2. As laminar families play an important role in network design problems, obtaining a better ratio is a major open problem in network design. We give a (1 + ln 2)-approximation algorithm for trees of constant radius. Our algorithm is based on a new decomposition of problem solutions, which may be of independent interest.