Aktiviteter pr. år
Abstract
The advice complexity of an online problem is a measure of how much knowledge of the future an online algorithm needs in order to achieve a certain competitive ratio. We determine the advice complexity of a number of hard online problems including independent set, vertex cover, dominating set and several others. These problems are hard, since a single wrong answer by the online algorithm can have devastating consequences. For each of these problems, we show that log (1 + (c1) ^{c1}/c ^{c} n = Θ(n/c) bits of advice are necessary and sufficient (up to an additive term of O(log n)) to achieve a competitive ratio of c. This is done by introducing a new string guessing problem related to those of Emek et al. (TCS 2011) and Böckenhauer et al. (TCS 2014). It turns out that this gives a powerful but easytouse method for providing both upper and lower bounds on the advice complexity of an entire class of online problems. Previous results of Halldórsson et al. (TCS 2002) on online independent set, in a related model, imply that the advice complexity of the problem is Θ(n/c). Our results improve on this by providing an exact formula for the higherorder term. Böckenhauer et al. (ISAAC 2009) gave a lower bound of Ω(n/c) and an upper bound of O((n log c)/c) on the advice complexity of online disjoint path allocation. We improve on the upper bound by a factor of log c. For the remaining problems, no bounds on their advice complexity were previously known.
Originalsprog  Engelsk 

Titel  32nd International Symposium on Theoretical Aspects of Computer Science (STACS 2015) 
Redaktører  Ernst W. Mayr, Nicolas Ollinger 
Vol/bind  30 
Forlag  Schloss DagstuhlLeibnizZentrum fuer Informatik 
Publikationsdato  2015 
Sider  116129 
ISBN (Elektronisk)  9783939897781 
DOI  
Status  Udgivet  2015 
Begivenhed  32nd International Symposium on Theoretical Aspects of Computer Science  Technische Universität München, Garching, Tyskland Varighed: 4. mar. 2015 → 7. mar. 2015 
Konference
Konference  32nd International Symposium on Theoretical Aspects of Computer Science 

Lokation  Technische Universität München 
Land/Område  Tyskland 
By  Garching 
Periode  04/03/2015 → 07/03/2015 
Navn  Leibniz International Proceedings in Informatics 

Vol/bind  30 
ISSN  18688969 
Emneord
 online algorithms
 advice complexity
 string guessing
 graph problems
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