A box-consistency contractor based on extremal functions

  • Authors:
  • Gilles Trombettoni;Yves Papegay;Gilles Chabert;Odile Pourtallier

  • Affiliations:
  • COPRIN, INRIA, Université Nice-Sophia, LINA, Ecole des Mines de Nantes;COPRIN, INRIA, Université Nice-Sophia, LINA, Ecole des Mines de Nantes;COPRIN, INRIA, Université Nice-Sophia, LINA, Ecole des Mines de Nantes;COPRIN, INRIA, Université Nice-Sophia, LINA, Ecole des Mines de Nantes

  • Venue:
  • CP'10 Proceedings of the 16th international conference on Principles and practice of constraint programming
  • Year:
  • 2010

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Abstract

Interval-based methods can approximate all the real solutions of a system of equations and inequalities. The Box interval constraint propagation algorithm enforces Box consistency. Itsmain procedure BoxNarrow handles one function f corresponding to the revised constraint, and one variable x, replacing the other variables of f by their current intervals. This paper proposes an improved BoxNarrow procedure for narrowing the domain of x when f respects certain conditions. In particular, these conditions are fulfilled when f is polynomial. f is first symbolically rewritten into a new form g. A narrowing step is then run on the non-interval extremal functions that enclose the interval function g. The corresponding algorithm is described and validated on several numerical constraint systems.