Acta Informatica

, Volume 6, Issue 1, pp 1–14 | Cite as

Algorithms minimizing mean flow time: schedule-length properties

  • E. G. CoffmanJr.
  • Ravi Sethi


The mean flow time of a schedule provides a measure of the average time that a task spends within a computer system, and also the average number of unfinished tasks in the system. The mean flow time of a schedule is defined to be the sum of the finishing times of all tasks in the system. On a system of identical processors O(nlog n) algorithms exist for determining minimal mean flow time schedules for n independent tasks. In general, there will be a large class C of schedules, of widely differing lengths, that all minimize mean flow time. The problem of finding the shortest schedule in C is NP-complete. We give heuristics that find schedules in C that are no more than 25% longer than the shortest schedule in C. The advantage of a short schedule is that processor utilization is high.


Information System Operating System Data Structure Communication Network Information Theory 
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Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • E. G. CoffmanJr.
    • 1
  • Ravi Sethi
    • 1
  1. 1.Computer Science Dept.The Pennsylvania State Univ.PennsylvaniaUSA

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