A scalable sweep algorithm for the cumulative constraint

  • Authors:
  • Arnaud Letort;Nicolas Beldiceanu;Mats Carlsson

  • Affiliations:
  • TASC team, (EMN-INRIA, LINA) Mines de Nantes, France;TASC team, (EMN-INRIA, LINA) Mines de Nantes, France;SICS, Kista, Sweden

  • Venue:
  • CP'12 Proceedings of the 18th international conference on Principles and Practice of Constraint Programming
  • Year:
  • 2012

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Abstract

This paper presents a sweep based algorithm for the cumulative constraint, which can operate in filtering mode as well as in greedy assignment mode. Given n tasks, this algorithm has a worst-case time complexity of O(n2). In practice, we use a variant with better average-case complexity but worst-case complexity of O(n2 logn), which goes down to O(n logn) when all tasks have unit duration, i.e. in the bin-packing case. Despite its worst-case time complexity, this algorithm scales well in practice, even when a significant number of tasks can be scheduled in parallel. It handles up to 1 million tasks in one single cumulative constraint in both Choco and SICStus.