## Abstract

A Constraint Satisfaction Problem is defined by a set of variables and a set of constraints, each variable has a nonempty domain of possible values. Each constraint involves some subset of the variables and specifies the allowable combinations of values for that subset. A solution of the problem is defined by an assignment of values to some or all of the variables that does not violate any constraints. To solve an instance, a search tree is created and each node in the tree represents a variable of the instance. The order in which the variables are selected for instantiation changes the form of the search tree and affects the cost of finding a solution. In this paper we explore the use of a Choice Function to dynamically select from a set of variable ordering heuristics the one that best matches the current problem state in order to show an acceptable performance over a wide range of instances. The Choice Function is defined as a weighted sum of process indicators expressing the recent improvement produced by the heuristic recently used. The weights are determined by a Particle Swarm Optimization algorithm in a multilevel approach. We report results where our combination of strategies outperforms the use of individual strategies.

Original language | English |
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Pages (from-to) | 1690-1695 |

Number of pages | 6 |

Journal | Expert Systems with Applications |

Volume | 40 |

Issue number | 5 |

DOIs | |

State | Published - Apr 2013 |

Externally published | Yes |

## Keywords

- Combinatorial optimization
- Constraints satisfaction
- Hyperheuristics
- Particle Swarm