Reoptimization gaps versus model errors in online-dispatching of service units for ADAC

  • Authors:
  • Benjamin Hiller;Sven O. Krumke;Jörg Rambau

  • Affiliations:
  • Department Optimization, Zuse-Institute Berlin, Germany;Department of Mathematics, University of Kaiserslautern, Germany;Department of Mathematics, University of Bayreuth, Germany

  • Venue:
  • Discrete Applied Mathematics - Special issue: Traces of the Latin American conference on combinatorics, graphs and applications: a selection of papers from LACGA 2004, Santiago, Chile
  • Year:
  • 2006

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Abstract

Under high load, the automated dispatching of service vehicles for the German Automobile Association (ADAC) must reoptimize a dispatch for 100-150 vehicles and 400 requests in about 10s to near optimality. In the presence of service contractors, this can be achieved by the column generation algorithm ZIBDIP. In metropolitan areas, however, service contractors cannot be dispatched automatically because they may decline. The problem: a model without contractors yields larger optimality gaps within 10s. One way out are simplified reoptimization models. These compute a short-term dispatch containing only some of the requests: unknown future requests will influence future service anyway. The simpler the models the better the gaps, but also the larger the model error. What is more significant: reoptimization gap or reoptimization model error? We answer this question in simulations on real-world ADAC data: only the new models ShadowPrice and ZIBDIPdummy can keep up with ZIBDIP.