Solving the Kirkman's Schoolgirl Problem in a Few Seconds

  • Authors:
  • Nicolas Barnier;Pascal Brisset

  • Affiliations:
  • -;-

  • Venue:
  • CP '02 Proceedings of the 8th International Conference on Principles and Practice of Constraint Programming
  • Year:
  • 2002

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Abstract

The Social Golfer Problem has been extensivelyu sed in recent years byt he constraint communityas an example of highlysy mmetric problem. It is an excellent problem for benchmarking symmetry breaking mechanisms such as SBDS or SBDD and for demonstrating the importance of the choice of the right model for one problem. We address in this paper a specific instance of the Golfer Problem well known as the Kirkman's Schoolgirl Problem and list a collection of techniques and tricks to find efficientlya ll its unique solutions. In particular, we propose SBDD+, an generic improvement over SBDD which allows a deep pruning when a symmetry is detected during the search. Our implementation of the presented techniques allows us to improve previous published results bya n order of magnitude for CPU time as well as number of backtracks, and to compute the seven unique solutions of the Kirkman's problem in a few seconds.