Competitive algorithms for server problems
Journal of Algorithms
An optimal on-line algorithm for K-servers on trees
SIAM Journal on Computing
New results on server problems
SIAM Journal on Discrete Mathematics
Journal of the ACM (JACM)
Online computation and competitive analysis
Online computation and competitive analysis
The harmonic k-server algorithm is competitive
Journal of the ACM (JACM)
Theoretical Computer Science - Special issue: Online algorithms in memoriam, Steve Seiden
The CNN problem and other k-server variants
Theoretical Computer Science - Special issue: Online algorithms in memoriam, Steve Seiden
A competitive algorithm for the general 2-server problem
ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
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We consider the CNN problem in arbitrary dimension, and over any metric space containing the integers. We prove that, in every dimension at least 2, no memoryless online algorithm can achieve a constant competitive ratio, under a weak symmetry constraint on the algorithm. This generalizes in several aspects the lower bounds obtained by Koutsoupias and Taylor [The CNN Problem and other k-server variants, Theoret. Comput. Sci. 324 (2004) 347-359] for the original problem. The proof consists in the analysis of carefully selected random walks, which appear naturally in the framework of memoryless algorithms.