Solving scheduling problems by untimed model checking: The clinical chemical analyser case study

  • Authors:
  • Anton J. Wijs;Jaco C. van de Pol;Elena M. Bortnik

  • Affiliations:
  • INRIA/VASY, 655, Avenue de l’Europe, 38330, Montbonnot St. Martin, France;University of Twente, Faculty EEMCS, P.O. Box 217, 7500 AE, Enschede, The Netherlands;Takumi Technology B.V., Marinus van Meelweg 19a, 5657 EN, Eindhoven, The Netherlands

  • Venue:
  • International Journal on Software Tools for Technology Transfer (STTT) - Special Section on FMICS 05
  • Year:
  • 2009

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Abstract

In this article, we show how scheduling problems can be modelled in untimed process algebra, by using special tick actions. A minimal-cost trace leading to a particular action, is one that minimises the number of tick steps. As a result, we can use any (timed or untimed) model checking tool to find shortest schedules. Instantiating this scheme to μCRL, we profit from a richer specification language than timed model checkers usually offer. Also, we can profit from efficient distributed state space generators. We propose a variant of breadth-first search that visits all states between consecutive tick steps, before moving to the next time slice. We experimented with a sequential and a distributed implementation of this algorithm. In addition, we experimented with beam search, which visits only parts of the search space, to find near-optimal solutions. Our approach is applied to find optimal schedules for test batches of a realistic clinical chemical analyser, which performs several kinds of tests on patient samples.