58 research outputs found
Experimental Evaluation of Branching Schemes for the CSP
The search strategy of a CP solver is determined by the variable and value
ordering heuristics it employs and by the branching scheme it follows. Although
the effects of variable and value ordering heuristics on search effort have
been widely studied, the effects of different branching schemes have received
less attention. In this paper we study this effect through an experimental
evaluation that includes standard branching schemes such as 2-way, d-way, and
dichotomic domain splitting, as well as variations of set branching where
branching is performed on sets of values. We also propose and evaluate a
generic approach to set branching where the partition of a domain into sets is
created using the scores assigned to values by a value ordering heuristic, and
a clustering algorithm from machine learning. Experimental results demonstrate
that although exponential differences between branching schemes, as predicted
in theory between 2-way and d-way branching, are not very common, still the
choice of branching scheme can make quite a difference on certain classes of
problems. Set branching methods are very competitive with 2-way branching and
outperform it on some problem classes. A statistical analysis of the results
reveals that our generic clustering-based set branching method is the best
among the methods compared.Comment: To appear in the 3rd workshop on techniques for implementing
constraint programming systems (TRICS workshop at the 16th CP Conference),
St. Andrews, Scotland 201
Optimal Placement of Valves in a Water Distribution Network with CLP(FD)
This paper presents a new application of logic programming to a real-life
problem in hydraulic engineering. The work is developed as a collaboration of
computer scientists and hydraulic engineers, and applies Constraint Logic
Programming to solve a hard combinatorial problem. This application deals with
one aspect of the design of a water distribution network, i.e., the valve
isolation system design.
We take the formulation of the problem by Giustolisi and Savic (2008) and
show how, thanks to constraint propagation, we can get better solutions than
the best solution known in the literature for the Apulian distribution network.
We believe that the area of the so-called hydroinformatics can benefit from
the techniques developed in Constraint Logic Programming and possibly from
other areas of logic programming, such as Answer Set Programming.Comment: Best paper award at the 27th International Conference on Logic
Programming - ICLP 2011; Theory and Practice of Logic Programming, (ICLP'11)
Special Issue, volume 11, issue 4-5, 201
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