Chapter 7. Configuring the Red Hat Build of OptaPlanner solver

Procedure

1. Build a Solver instance with the SolverFactory.

2. Configure the solver configuration XML file:

   1. Define the model.
   2. Define the score function.

   3. Optional: Configure the optimization algorithm.

      The following example is a solver XML file for the NQueens problem:

      <?xml version="1.0" encoding="UTF-8"?>
      <solver xmlns="https://www.optaplanner.org/xsd/solver" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="https://www.optaplanner.org/xsd/solver https://www.optaplanner.org/xsd/solver/solver.xsd">
        <!-- Define the model -->
        <solutionClass>org.optaplanner.examples.nqueens.domain.NQueens</solutionClass>
        <entityClass>org.optaplanner.examples.nqueens.domain.Queen</entityClass>
      
        <!-- Define the score function -->
        <scoreDirectorFactory>
          <scoreDrl>org/optaplanner/examples/nqueens/optional/nQueensConstraints.drl</scoreDrl>
        </scoreDirectorFactory>
      
        <!-- Configure the optimization algorithms (optional) -->
        <termination>
          ...
        </termination>
        <constructionHeuristic>
          ...
        </constructionHeuristic>
        <localSearch>
          ...
        </localSearch>
      </solver>

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      Note

      On some environments, for example OSGi and JBoss modules, classpath resources such as the solver config, score DRLs, and domain classe) in your JAR files might not be available to the default ClassLoader of the optaplanner-core JAR file. In those cases, provide the ClassLoader of your classes as a parameter:

             SolverFactory<NQueens> solverFactory = SolverFactory.createFromXmlResource(
                     ".../nqueensSolverConfig.xml", getClass().getClassLoader());

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3. Configure the SolverFactory with a solver configuration XML file, provided as a classpath resource as defined by ClassLoader.getResource():

          SolverFasctory<NQueens> solverFactory = SolverFactory.createFromXmlResource(
                  "org/optaplanner/examples/nqueens/optional/nqueensSolverConfig.xml");
          Solver<NQueens> solver = solverFactory.buildSolver();

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Procedure

1. Add a custom property.

   For example, if your EasyScoreCalculator has heavy calculations which are cached and you want to increase the cache size in one benchmark add the myCacheSize property:

     <scoreDirectorFactory>
       <easyScoreCalculatorClass>...MyEasyScoreCalculator</easyScoreCalculatorClass>
       <easyScoreCalculatorCustomProperties>
         <property name="myCacheSize" value="1000"/><!-- Override value -->
       </easyScoreCalculatorCustomProperties>
     </scoreDirectorFactory>

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2. Add a public setter for each custom property, which is called when a Solver is built.

   public class MyEasyScoreCalculator extends EasyScoreCalculator<MySolution, SimpleScore> {
   
           private int myCacheSize = 500; // Default value
   
           @SuppressWarnings("unused")
           public void setMyCacheSize(int myCacheSize) {
               this.myCacheSize = myCacheSize;
           }
   
       ...
   }

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   Most value types are supported, including boolean, int, double, BigDecimal, String and enums.