Acta Informatica

, Volume 39, Issue 8, pp 597–612

Ideal preemptive schedules on two processors

Original Paper


An ideal schedule minimizes both makespan and total flow time. It is known that the Coffman-Graham algorithm [Acta Informatica1, 200-213, 1972] solves in polynomial time the problem of finding an ideal nonpreemptive schedule of unit-execution-time jobs with equal release dates and arbitrary precedence constraints on two identical parallel processors. This paper presents an extension of the algorithm that solves in polynomial time the preemptive counterpart of this problem. The complexity status of the preemptive problem of minimizing just the total flow time has been open.


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Copyright information

© Springer-Verlag Berlin/Heidelberg 2003

Authors and Affiliations

  • E. G. Coffman
    • 1
  • J. Sethuraman
    • 2
  • V. G. Timkovsky
    • 3
    • 4
  1. 1.Department of Electrical EngineeringColumbia UniversityNew YorkUSA
  2. 2.Department of Industrial Engineering & Operations ResearchColumbia UniversityNew YorkUSA
  3. 3.Department of Industrial Engineering & Operations ResearchCGI Group Inc.TorontoCanada 1G1
  4. 4.Department of Computing & SoftwareMcMaster UniversityHamiltonCanada

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