Neighbourhood Based Robustness Applied to Tardiness and Total Flowtime Job Shops

  • Authors:
  • Mikkel T. Jensen

  • Affiliations:
  • -

  • Venue:
  • PPSN VI Proceedings of the 6th International Conference on Parallel Problem Solving from Nature
  • Year:
  • 2000

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Abstract

The traditional focus of scheduling research is finding schedules with a low implementation cost. However, in many real world scheduling applications finding a robust schedule (a quality schedule expected to still be acceptable if something unforeseen happens) or a flexible schedule (a quality schedule expected to be easy to change) is just as important. In this paper the robustness and flexibility of schedules produced by minimizing neighbourhood based robustness measures are investigated. The basic idea is to minimize not only the implementation cost of a single schedule, but the implementation costs of a set of schedules located around a centre schedule. The problems used in the experiments are worst tardiness, summed tardiness and total flow time job shop problems. It is found that the robustness measures increase robustness and to some degree flexibility for worst tardiness and loose summed tardiness problems, while they do not perform well for tight summed tardiness problems and total flow time problems. It is conjectured that neighbourhood based robustness can be expected to work well on problems with few critical points and not well on problems with many critical points.