2014 | OriginalPaper | Chapter
On Streaming and Communication Complexity of the Set Cover Problem
Authors : Erik D. Demaine, Piotr Indyk, Sepideh Mahabadi, Ali Vakilian
Published in: Distributed Computing
Publisher: Springer Berlin Heidelberg
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We develop the first streaming algorithm and the first two-party communication protocol that uses a constant number of passes/rounds and sublinear space/communication for logarithmic approximation to the classic Set Cover problem. Specifically, for
n
elements and
m
sets, our algorithm/protocol achieves a space bound of
O
(
m
·
n
δ
log
2
n
log
m
) using
O
(4
1/
δ
) passes/rounds while achieving an approximation factor of
O
(4
1/
δ
log
n
) in polynomial time (for
δ
= Ω(1/log
n
)). If we allow the algorithm/protocol to spend exponential time per pass/round, we achieve an approximation factor of
O
(4
1/
δ
). Our approach uses randomization, which we show is necessary: no deterministic constant approximation is possible (even given exponential time) using
o
(
m
n
) space. These results are some of the first on streaming algorithms and efficient two-party communication protocols for approximation algorithms. Moreover, we show that our algorithm can be applied to multi-party communication model.