Complete characterization of near-optimal sequences for the two-machine flow shop scheduling problem

  • Authors:
  • Jean-Charles Billaut;Emmanuel Hebrard;Pierre Lopez

  • Affiliations:
  • Laboratoire d'Informatique, Université François-Rabelais Tours, Tours, France;CNRS, LAAS, Toulouse, France,Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, Toulouse, France;CNRS, LAAS, Toulouse, France,Université de Toulouse, UPS, INSA, INP, ISAE, UT1, UTM, LAAS, Toulouse, France

  • Venue:
  • CPAIOR'12 Proceedings of the 9th international conference on Integration of AI and OR Techniques in Constraint Programming for Combinatorial Optimization Problems
  • Year:
  • 2012

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Abstract

In a two-machine flow shop scheduling problem, the set of ε -approximate sequences (i.e. , solutions within a factor 1+ε of the optimal) can be mapped to the vertices of a permutation lattice. We introduce two approaches, based on properties derived from the analysis of permutation lattices, for characterizing large sets of near-optimal solutions. In the first approach, we look for a sequence of minimum level in the lattice, since this solution is likely to cover many optimal or near-optimal solutions. In the second approach, we look for all sequences of minimal level, thus covering all ε -approximate sequences. Integer linear programming and constraint programming models are first proposed to solve the former problem. For the latter problem, a direct exploration of the lattice, traversing it by a simple tree search procedure, is proposed. Computational experiments are given to evaluate these methods and to illustrate the interest and the limits of such approaches.