[rules-users] Simple Drools Planner Example with NQueens

[morge]

Hi all,

I am currently looking at Drools planner. I try to solve a simple 4 queens
problem with the following
code:

XmlSolverConfigurer configurer = new XmlSolverConfigurer();
configurer.configure("/org/drools/planner/myexamples/nqueens/app/nqueensSolverConfig.xml");
Solver solver = configurer.buildSolver();
NQueensGenerator generator=new NQueensGenerator();
Solution startingSolution = generator.createNQueens(4);
solver.setStartingSolution(startingSolution);
solver.solve();
Solution bestSolution = solver.getBestSolution();
System.out.println((NQueens) bestSolution);	

The config file is the usual one:
<?xml version="1.0" encoding="UTF-8"?>
<localSearchSolver>
    <environmentMode>DEBUG</environmentMode>
   
<scoreDrl>/org/drools/planner/examples/nqueens/solver/nQueensScoreRules.drl</scoreDrl>
    <scoreDefinition>
        <scoreDefinitionType>SIMPLE</scoreDefinitionType>
    </scoreDefinition>
    <!-- Real world problems require to use of
<startingSolutionInitializerClass>. -->
    <termination>
        <terminationCompositionStyle>OR</terminationCompositionStyle>
        <maximumStepCount>100</maximumStepCount>
        <scoreAttained>0</scoreAttained>
    </termination>
    <selector>
       
<moveFactoryClass>org.drools.planner.examples.nqueens.solver.move.factory.NQueensMoveFactory</moveFactoryClass>
    </selector>
    <acceptor>
        <completeSolutionTabuSize>1000</completeSolutionTabuSize>
    </acceptor>
    <forager>
        <pickEarlyType>NEVER</pickEarlyType>
        <!-- Real world problems require to use of
<minimalAcceptedSelection> -->
    </forager>
</localSearchSolver>


I do not understand why but it does not work:

2010-11-17 11:15:13,791 [main] INFO  Solving with random seed (0).
2010-11-17 11:15:13,793 [main] INFO  Initialization time spend (4) for score
(0). Updating best solution and best score.
Exception in thread "main" java.lang.ClassCastException:
org.drools.planner.myexamples.nqueens.domain.NQueens
	at
org.drools.planner.examples.nqueens.solver.move.factory.NQueensMoveFactory.createCachedMoveList(NQueensMoveFactory.java:35)
	at
org.drools.planner.core.move.factory.CachedMoveFactory.solvingStarted(CachedMoveFactory.java:39)
	at
org.drools.planner.core.localsearch.decider.selector.MoveFactorySelector.solvingStarted(MoveFactorySelector.java:58)
	at
org.drools.planner.core.localsearch.decider.DefaultDecider.solvingStarted(DefaultDecider.java:91)
	at
org.drools.planner.core.localsearch.DefaultLocalSearchSolver.solvingStarted(DefaultLocalSearchSolver.java:188)
	at
org.drools.planner.core.localsearch.DefaultLocalSearchSolver.solveImplementation(DefaultLocalSearchSolver.java:125)
	at org.drools.planner.core.AbstractSolver.solve(AbstractSolver.java:57)
	at org.drools.planner.myexamples.nqueens.app.Main.main(Main.java:32)


Any idea ?

Thanks in advance,


MM.
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