Online parallel scheduling of non-uniform tasks: Trading failures for energy

Antonio Fernández Anta, Chryssis Georgiou, Dariusz R. Kowalski, Elli Zavou

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations


Consider a system in which tasks of different execution times arrive continuously and have to be executed by a set of processors that are prone to crashes and restarts. In this paper we model and study the impact of parallelism and failures on the competitiveness of such an online system. In a fault-free environment, a simple Longest-in-System scheduling policy, enhanced by a redundancy-avoidance mechanism, guarantees optimality in a long-term execution. In the presence of failures though, scheduling becomes a much more challenging task. In particular, no parallel deterministic algorithm can be competitive against an offline optimal solution, even with one single processor and tasks of only two different execution times. We find that when additional energy is provided to the system in the form of processor speedup, the situation changes. Specifically, we identify thresholds on the speedup under which such competitiveness cannot be achieved by any deterministic algorithm, and above which competitive algorithms exist. Finally, we propose algorithms that achieve small bounded competitive ratios when the speedup is over the threshold.

Original languageEnglish (US)
Title of host publicationFundamentals of Computation Theory - 19th International Symposium, FCT 2013, Proceedings
Number of pages14
StatePublished - 2013
Externally publishedYes
Event19th International Symposium on Fundamentals of Computation Theory, FCT 2013 - Liverpool, United Kingdom
Duration: Aug 19 2013Aug 21 2013

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume8070 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference19th International Symposium on Fundamentals of Computation Theory, FCT 2013
Country/TerritoryUnited Kingdom


  • Competitiveness
  • Energy Efficiency
  • Failures
  • Non-uniform Tasks
  • Online Algorithms
  • Scheduling

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)


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