Preemptive online scheduling with reordering

György Dósa, Leah Epstein

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


We consider online preemptive scheduling of jobs, arriving one by one, on m identical parallel machines. A buffer of a positive fixed size, K, which assists in partial reordering of the input, is available for the storage of at most K unscheduled jobs. We study the effect of using a fixed sized buffer (of an arbitrary size) on the supremum competitive ratio over all numbers of machines (the overall competitive ratio), as well as the effect on the competitive ratio as a function of m. We find a tight bound on the competitive ratio for any m. This bound is for even values of m and slightly lower for odd values of m. We show that a buffer of size Θ(m) is sufficient to achieve this bound, but using K=o(m) does not reduce the best overall competitive ratio which is known for the case without reordering, . We further consider the semi-online variant where jobs arrive sorted by non-increasing processing time requirements. In this case we show that it is possible to achieve a competitive ratio of 1. In addition, we find tight bounds as a function of both K and m.

Original languageEnglish
Title of host publicationAlgorithms - ESA 2009 - 17th Annual European Symposium, Proceedings
Number of pages12
StatePublished - 2009
Event17th Annual European Symposium on Algorithms, ESA 2009 - Copenhagen, Denmark
Duration: 7 Sep 20099 Sep 2009

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume5757 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference17th Annual European Symposium on Algorithms, ESA 2009

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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