Reasoning on Sequences in Constraint-Based Local Search Frameworks

Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10848)


This paper explains why global constraints for routing cannot be integrated into Constraint-Based Local Search (CBLS) frameworks. A technical reason for this is identified and defined as the multi-variable bottleneck. We solve this bottleneck by introducing a new type of variables: “sequence of integers”. We identify key requirements and defines a vocabulary for this variable type, through which it communicates with global constraints. Dedicated data structures are designed for efficiently representing sequences in this context. Benchmarks are presented to identify how to best parametrise those data structures and to compare our approach with other state-of-the-art local search frameworks: LocalSolver and GoogleCP. Our contribution is included in the CBLS engine of the open source OscaR framework.


Local search CBLS Global constraints Sequences OscaR.cbls 



This research was conducted under the SAMOBI CWALITY (grant nr. 1610019) and the PRIMa-Q CORNET (grant nr. 1610088) research projects from the Walloon Region of Belgium. We thank YourKit profiler and LocalSolver for making their software freely available to us for this research. We also warmly thank Pierre Flener and the anonymous referees for their feedback on earlier versions of this work.


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.CETIC Research CentreCharleroiBelgium

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