MLATCS - Součastné doktorské disertace
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Thesis MLATCS 2011
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Tomáš Ebenlendr
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Combinatorial algorithms for online problems: Semi-online scheduling on related machines
- Supervisors :
Jiří Sgall
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Combinatorial algorithms for online problems: Semi-online scheduling on related machines Abstract of doctoral thesis We construct a framework that gives optimal algorithms for a whole class of scheduling problems. This class covers the most studied semi-online variants of preemptive online scheduling on uniformly related machines with the objective to minimize makespan. The algorithms from our framework are deterministic, yet they are optimal even among all randomized algorithms. In addition, they are optimal for any fixed combination of speeds of the machines, and thus our results subsume all the previous work on various special cases. We provide new lower bound of 2.112 for the original online problem. The (deterministic) upper bound is e ≈ 2.718 as there was known e-competitive randomized algorithm before. Our framework applies to all semi-online variants which are based on some knowledge about the input sequence. I.e., they are restrictions of the set of valid inputs. We use our framework to study restrictions that were studied before, and we derive some new bounds. Namely we study known sum of processing times, known maximal processing time, sorted (decreasing) jobs, tightly grouped processing times, approximately known optimal makespan and few combinations. Based on the analysis of this algorithm, we derive some global relations between various semi-online restrictions. The framework uses linear programs to compute the optimal competitive...
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Defense
27/06/2011, MFF UK Praha
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EN
