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Solving Very Large
Crew Scheduling Problems to Optimality

Tallys H. Yunes1

Arnaldo V. Moura

Cid C. de Souza2

Institute of Computing, University of Campinas
P.O. Box 6176, ZIP 13083-970
Campinas, SP, Brazil


In this article, we present a hybrid methodology for the exact solution of large scale real world crew scheduling problems. Our approach integrates mathematical programming and constraint satisfaction techniques, taking advantage of their particular abilities in modeling and solving specific parts of the problem. An Integer Programming framework was responsible for guiding the overall search process and for obtaining lower bounds on the value of the optimal solution. Complex constraints were easily expressed, in a declarative way, using a Constraint Logic Programming language. Moreover, with an effective constraint-based model, the huge space of feasible solutions could be implicitly considered in a fairly efficient way. Our code was tested on real problem instances arising from the daily operation of an ordinary urban transit company that serves a major metropolitan area with an excess of two million inhabitants. Using a typical desktop PC, we were able find, in an acceptable running time, an optimal solution to instances with more than 1.5 billion entries.

Keywords: Crew Scheduling, Constraint Programming, Mathematical Programming, Hybrid Algorithms, Column Generation

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Next: Introduction