OptaPlanner

https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/
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OptaPlanner is a constraint-solving AI optimization engine for solving NP-hard planning problems...
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### Run OptaPlanner Examples via Shell

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Execute the examples GUI application using the provided shell scripts.

```bash
$ cd examples
$ ./runExamples.sh
```

```batch
$ cd examples
$ runExamples.bat
```

--------------------------------

### Example CloudBalancePartitioner Implementation

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

A concrete implementation of the SolutionPartitioner interface for the CloudBalance example.

```java
public class CloudBalancePartitioner implements SolutionPartitioner<CloudBalance> {

    private int partCount = 4;
    private int minimumProcessListSize = 75;

    @Override
    public List<CloudBalance> splitWorkingSolution(ScoreDirector<CloudBalance> scoreDirector, Integer runnablePartThreadLimit) {
        CloudBalance originalSolution = scoreDirector.getWorkingSolution();
        List<CloudComputer> originalComputerList = originalSolution.getComputerList();
        List<CloudProcess> originalProcessList = originalSolution.getProcessList();
        int partCount = this.partCount;
        if (originalProcessList.size() / partCount < minimumProcessListSize) {
            partCount = originalProcessList.size() / minimumProcessListSize;
        }
        List<CloudBalance> partList = new ArrayList<>(partCount);
        for (int i = 0; i < partCount; i++) {
            CloudBalance partSolution = new CloudBalance(originalSolution.getId(),
                    new ArrayList<>(originalComputerList.size() / partCount + 1),
                    new ArrayList<>(originalProcessList.size() / partCount + 1));
            partList.add(partSolution);
        }

        int partIndex = 0;
        Map<Long, Pair<Integer, CloudComputer>> idToPartIndexAndComputerMap = new HashMap<>(originalComputerList.size());
        for (CloudComputer originalComputer : originalComputerList) {
            CloudBalance part = partList.get(partIndex);
            CloudComputer computer = new CloudComputer(
                    originalComputer.getId(),
                    originalComputer.getCpuPower(), originalComputer.getMemory(),
                    originalComputer.getNetworkBandwidth(), originalComputer.getCost());
            part.getComputerList().add(computer);
            idToPartIndexAndComputerMap.put(computer.getId(), Pair.of(partIndex, computer));
            partIndex = (partIndex + 1) % partList.size();
        }
```

--------------------------------

### Clone Quickstarts Repository

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Command to clone the OptaPlanner quickstarts repository from GitHub.

```bash
$ git clone https://github.com/kiegroup/optaplanner-quickstarts
```

--------------------------------

### SimpleScore Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of using SimpleScore in a planning solution.

```java
    @PlanningScore
    private SimpleScore score;
```

--------------------------------

### Implement CustomPhaseCommand

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of a custom phase command to initialize machine assignments.

```java
public class ToOriginalMachineSolutionInitializer extends AbstractCustomPhaseCommand<MachineReassignment> {

    public void changeWorkingSolution(ScoreDirector<MachineReassignment> scoreDirector) {
        MachineReassignment machineReassignment = scoreDirector.getWorkingSolution();
        for (MrProcessAssignment processAssignment : machineReassignment.getProcessAssignmentList()) {
            scoreDirector.beforeVariableChanged(processAssignment, "machine");
            processAssignment.setMachine(processAssignment.getOriginalMachine());
            scoreDirector.afterVariableChanged(processAssignment, "machine");
            scoreDirector.triggerVariableListeners();
        }
    }
```

--------------------------------

### Build and Run OptaPlanner from Source

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Commands to clone, build, and execute the OptaPlanner examples from the source repository.

```bash
$ git clone https://github.com/kiegroup/optaplanner.git
...
```

```bash
$ cd optaplanner
$ mvn clean install -DskipTests
...
```

```bash
$ cd optaplanner-examples
$ mvn exec:java
...
```

--------------------------------

### View Hello World Output

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example log output showing the optimized school timetable schedule.

```text
... 
INFO  Solving ended: time spent (5000), best score (0hard/9soft), ... 
INFO 
INFO  |            | Room A     | Room B     | Room C     | 
INFO  |------------|------------|------------|------------| 
INFO  | MON 08:30  | English    | Math       |            | 
INFO  |            | I. Jones   | A. Turing  |            | 
INFO  |            | 9th grade  | 10th grade |            | 
INFO  |------------|------------|------------|------------| 
INFO  | MON 09:30  | History    | Physics    |            | 
INFO  |            | I. Jones   | M. Curie   |            | 
INFO  |            | 9th grade  | 10th grade |            | 
INFO  |------------|------------|------------|------------| 
INFO  | MON 10:30  | History    | Physics    |            | 
INFO  |            | I. Jones   | M. Curie   |            | 
INFO  |            | 10th grade | 9th grade  |            | 
INFO  |------------|------------|------------|------------| 
... 
INFO  |------------|------------|------------|------------|
```

--------------------------------

### Implement ConstraintMatchAwareIncrementalScoreCalculator Example

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of the constraint match aware interface for a machine reassignment problem.

```java
public class MachineReassignmentIncrementalScoreCalculator
        implements ConstraintMatchAwareIncrementalScoreCalculator<MachineReassignment, HardSoftLongScore> {
    ...

    @Override
    public void resetWorkingSolution(MachineReassignment workingSolution, boolean constraintMatchEnabled) {
        resetWorkingSolution(workingSolution);
        // ignore constraintMatchEnabled, it is always presumed enabled
    }
```

--------------------------------

### Configure Simulated Annealing

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Basic configuration for simulated annealing using a starting temperature.

```xml
  <localSearch>
    ...
    <acceptor>
      <simulatedAnnealingStartingTemperature>2hard/100soft</simulatedAnnealingStartingTemperature>
    </acceptor>
    <forager>
      <acceptedCountLimit>1</acceptedCountLimit>
    </forager>
  </localSearch>
```

--------------------------------

### Initialize UniConstraintStream

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of starting a constraint stream with a single object type, resulting in a UniConstraintStream.

```java
    private Constraint doNotAssignAnn(ConstraintFactory factory) {
        return factory.forEach(Shift.class) // Returns UniStream<Shift>.
                ...
    }
```

--------------------------------

### Integrate Prometheus monitoring

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of setting up a Prometheus registry and exposing it via an HTTP server.

```java
PrometheusMeterRegistry prometheusRegistry = new PrometheusMeterRegistry(PrometheusConfig.DEFAULT);

try {
    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
    server.createContext("/prometheus", httpExchange -> {
        String response = prometheusRegistry.scrape(); (1)
        httpExchange.sendResponseHeaders(200, response.getBytes().length);
        try (OutputStream os = httpExchange.getResponseBody()) {
            os.write(response.getBytes());
        }
    });

    new Thread(server::start).start();
} catch (IOException e) {
    throw new RuntimeException(e);
}

Metrics.addRegistry(prometheusRegistry);
```

--------------------------------

### CloudBalancingHelloWorld Main Class

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

The complete main class for the Cloud Balancing Hello World example.

```java
public class CloudBalancingHelloWorld {

    public static void main(String[] args) {
        // Build the Solver
        SolverFactory<CloudBalance> solverFactory = SolverFactory.createFromXmlResource(
                "org/optaplanner/examples/cloudbalancing/solver/cloudBalancingSolverConfig.xml");
        Solver<CloudBalance> solver = solverFactory.buildSolver();

        // Load a problem with 400 computers and 1200 processes
        CloudBalance unsolvedCloudBalance = new CloudBalancingGenerator().createCloudBalance(400, 1200);

        // Solve the problem
        CloudBalance solvedCloudBalance = solver.solve(unsolvedCloudBalance);

        // Display the result
        System.out.println("\nSolved cloudBalance with 400 computers and 1200 processes:\n"
                + toDisplayString(solvedCloudBalance));
    }

    ...
}
```

--------------------------------

### View Application Console Output

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of the formatted console output displaying the generated timetable.

```text
...
INFO  |            | Room A     | Room B     | Room C     |
INFO  |------------|------------|------------|------------|
INFO  | MON 08:30  | English    | Math       |            |
INFO  |            | I. Jones   | A. Turing  |            |
INFO  |            | 9th grade  | 10th grade |            |
INFO  |------------|------------|------------|------------|
INFO  | MON 09:30  | History    | Physics    |            |
INFO  |            | I. Jones   | M. Curie   |            |
INFO  |            | 9th grade  | 10th grade |            |
...
```

--------------------------------

### Define Solver Benchmark Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a PlannerBenchmark configuration containing multiple solver benchmarks.

```xml
<solverBenchmark>
    <name>Tabu Search</name>
    <solver>
      ...<!-- Tabu Search specific solver configuration -->
    </solver>
  </solverBenchmark>
  <solverBenchmark>
    <name>Simulated Annealing</name>
    <solver>
      ...<!-- Simulated Annealing specific solver configuration -->
    </solver>
  </solverBenchmark>
  <solverBenchmark>
    <name>Late Acceptance</name>
    <solver>
      ...<!-- Late Acceptance specific solver configuration -->
    </solver>
  </solverBenchmark>
</plannerBenchmark>
```

--------------------------------

### HardSoftScore Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of using the recommended HardSoftScore in a planning solution.

```java
    @PlanningScore
    private HardSoftScore score;
```

--------------------------------

### Example Solver Log Output

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Sample output showing solver progress and score calculation speeds when debug logging is enabled.

```text
INFO  Solving started: time spent (3), best score (-4init/0), random (JDK with seed 0).
DEBUG     CH step (0), time spent (5), score (-3init/0), selected move count (1), picked move (Queen-2 {null -> Row-0}).
DEBUG     CH step (1), time spent (7), score (-2init/0), selected move count (3), picked move (Queen-1 {null -> Row-2}).
DEBUG     CH step (2), time spent (10), score (-1init/0), selected move count (4), picked move (Queen-3 {null -> Row-3}).
DEBUG     CH step (3), time spent (12), score (-1), selected move count (4), picked move (Queen-0 {null -> Row-1}).
INFO  Construction Heuristic phase (0) ended: time spent (12), best score (-1), score calculation speed (9000/sec), step total (4).
DEBUG     LS step (0), time spent (19), score (-1),     best score (-1), accepted/selected move count (12/12), picked move (Queen-1 {Row-2 -> Row-3}).
DEBUG     LS step (1), time spent (24), score (0), new best score (0), accepted/selected move count (9/12), picked move (Queen-3 {Row-3 -> Row-2}).
INFO  Local Search phase (1) ended: time spent (24), best score (0), score calculation speed (4000/sec), step total (2).
INFO  Solving ended: time spent (24), best score (0), score calculation speed (7000/sec), phase total (2), environment mode (REPRODUCIBLE).
```

--------------------------------

### Implement NQueens EasyScoreCalculator

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of an EasyScoreCalculator for the N Queens problem.

```java
public class NQueensEasyScoreCalculator
    implements EasyScoreCalculator<NQueens, SimpleScore> {

    @Override
    public SimpleScore calculateScore(NQueens nQueens) {
        int n = nQueens.getN();
        List<Queen> queenList = nQueens.getQueenList();
```

--------------------------------

### View solver step logs

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example output when using debug logging to track solver steps.

```text
... Solving started: time spent (67), best score (-20init/0hard/0soft), environment mode (REPRODUCIBLE), random (JDK with seed 0).
...     CH step (0), time spent (128), score (-18init/0hard/0soft), selected move count (15), picked move ([Math(101) {null -> Room A}, Math(101) {null -> MONDAY 08:30}]).
...     CH step (1), time spent (145), score (-16init/0hard/0soft), selected move count (15), picked move ([Physics(102) {null -> Room A}, Physics(102) {null -> MONDAY 09:30}]).
...
```

--------------------------------

### Preparing test data for constraints

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of creating planning entities for use in constraint verification tests.

```java
        Row row1 = new Row(0);
        Column column1 = new Column(0);
        Column column2 = new Column(1);
        Queen queen1 = new Queen(0, row1, column1);
        Queen queen2 = new Queen(1, row1, column2);
```

--------------------------------

### Configure Construction Heuristic with MoveSelectors

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Advanced configuration example for construction heuristics using custom MoveSelectors.

```xml
    <constructionHeuristicType>FIRST_FIT_DECREASING</constructionHeuristicType>
    <...MoveSelector/>
    <...MoveSelector/>
    ...
  </constructionHeuristic>
```

```xml
  <constructionHeuristic>
    <constructionHeuristicType>WEAKEST_FIT</constructionHeuristicType>
    <...MoveSelector/>
    <...MoveSelector/>
    ...
  </constructionHeuristic>
```

```xml
  <constructionHeuristic>
    <constructionHeuristicType>WEAKEST_FIT_DECREASING</constructionHeuristicType>
    <...MoveSelector/>
    <...MoveSelector/>
    ...
  </constructionHeuristic>
```

```xml
  <constructionHeuristic>
    <constructionHeuristicType>STRONGEST_FIT</constructionHeuristicType>
    <...MoveSelector/>
    <...MoveSelector/>
    ...
  </constructionHeuristic>
```

```xml
  <constructionHeuristic>
    <constructionHeuristicType>STRONGEST_FIT_DECREASING</constructionHeuristicType>
    <...MoveSelector/>
    <...MoveSelector/>
    ...
  </constructionHeuristic>
```

--------------------------------

### Configure Partitioned Search Phases

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a common configuration combining a Partitioned Search phase with a subsequent non-partitioned Local Search phase.

```xml
  <partitionedSearch>
    <solutionPartitionerClass>...CloudBalancePartitioner</solutionPartitionerClass>

    <constructionHeuristic/>
    <localSearch>
      <termination>
        <secondsSpentLimit>60</secondsSpentLimit>
      </termination>
    </localSearch>
  </partitionedSearch>
  <localSearch/>
```

--------------------------------

### Run the application in development mode

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Starts the Quarkus application using the Maven development profile.

```bash
$ mvn compile quarkus:dev
```

--------------------------------

### Nurse Rostering Dataset Sizes

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Examples of dataset configurations and their corresponding search space sizes.

```text
toy1          has 1 skills, 3 shiftTypes, 2 patterns, 1 contracts,  6 employees,  7 shiftDates,  35 shiftAssignments and   0 requests with a search space of   10^27.
toy2          has 1 skills, 3 shiftTypes, 3 patterns, 2 contracts, 20 employees, 28 shiftDates, 180 shiftAssignments and 140 requests with a search space of  10^234.
```

--------------------------------

### Enable Trace Logging for Decision Making

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of trace-level logs showing move evaluation, acceptance, and selection during the solver process.

```text
INFO  Solver started: time spent (0), score (-6), new best score (-6), random (JDK with seed 0).
TRACE         Move index (0) not doable, ignoring move (Queen-0 {Row-0 -> Row-0}).
TRACE         Move index (1), score (-4), accepted (true), move (Queen-0 {Row-0 -> Row-1}).
TRACE         Move index (2), score (-4), accepted (true), move (Queen-0 {Row-0 -> Row-2}).
TRACE         Move index (3), score (-4), accepted (true), move (Queen-0 {Row-0 -> Row-3}).
...
TRACE         Move index (6), score (-3), accepted (true), move (Queen-1 {Row-0 -> Row-3}).
...
TRACE         Move index (9), score (-3), accepted (true), move (Queen-2 {Row-0 -> Row-3}).
...
TRACE         Move index (12), score (-4), accepted (true), move (Queen-3 {Row-0 -> Row-3}).
DEBUG     LS step (0), time spent (6), score (-3), new best score (-3), accepted/selected move count (12/12), picked move (Queen-1 {Row-0 -> Row-3}).
...
```

--------------------------------

### Branch and Bound Node Exploration Types

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Examples of configuring different node exploration strategies for Branch and Bound.

```xml
  <exhaustiveSearch>
    <exhaustiveSearchType>BRANCH_AND_BOUND</exhaustiveSearchType>
    <nodeExplorationType>DEPTH_FIRST</nodeExplorationType>
  </exhaustiveSearch>
```

```xml
  <exhaustiveSearch>
    <exhaustiveSearchType>BRANCH_AND_BOUND</exhaustiveSearchType>
    <nodeExplorationType>BREADTH_FIRST</nodeExplorationType>
  </exhaustiveSearch>
```

```xml
  <exhaustiveSearch>
    <exhaustiveSearchType>BRANCH_AND_BOUND</exhaustiveSearchType>
    <nodeExplorationType>SCORE_FIRST</nodeExplorationType>
  </exhaustiveSearch>
```

--------------------------------

### Cloud Balancing Solver Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

The complete XML configuration file for the Cloud Balancing example, defining domain classes, score calculation, and termination limits.

```xml
<?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">
  <!-- Domain model configuration -->
  <solutionClass>org.optaplanner.examples.cloudbalancing.domain.CloudBalance</solutionClass>
  <entityClass>org.optaplanner.examples.cloudbalancing.domain.CloudProcess</entityClass>

  <!-- Score configuration -->
  <scoreDirectorFactory>
    <easyScoreCalculatorClass>org.optaplanner.examples.cloudbalancing.optional.score.CloudBalancingEasyScoreCalculator</easyScoreCalculatorClass>
    <!--<constraintProviderClass>org.optaplanner.examples.cloudbalancing.score.CloudBalancingConstraintProvider</constraintProviderClass>-->
  </scoreDirectorFactory>

  <!-- Optimization algorithms configuration -->
  <termination>
    <secondsSpentLimit>30</secondsSpentLimit>
  </termination>
</solver>
```

--------------------------------

### Enable Local Search Debug Logging

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of the log output when debug logging is enabled for the org.optaplanner category during local search.

```text
INFO  Solving started: time spent (0), best score (-6), environment mode (REPRODUCIBLE), random (JDK with seed 0).
DEBUG     LS step (0), time spent (20), score (-3), new best score (-3), accepted/selected move count (12/12), picked move (Queen-1 {Row-0 -> Row-3}).
DEBUG     LS step (1), time spent (31), score (-1), new best score (-1), accepted/selected move count (12/12), picked move (Queen-3 {Row-0 -> Row-2}).
DEBUG     LS step (2), time spent (40), score (0), new best score (0), accepted/selected move count (12/12), picked move (Queen-0 {Row-0 -> Row-1}).
```

--------------------------------

### Configure Solver and Phase Termination

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of defining termination limits for both the entire Solver and specific Local Search phases within an XML configuration.

```xml
<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">
  ...
  <termination><!-- Solver termination -->
    <secondsSpentLimit>90</secondsSpentLimit>
  </termination>
  <localSearch>
    <termination><!-- Phase termination -->
      <secondsSpentLimit>60</secondsSpentLimit><!-- Give the next phase a chance to run too, before the Solver terminates -->
    </termination>
    ...
  </localSearch>
  <localSearch>
    ...
  </localSearch>
</solver>
```

--------------------------------

### Log4j 1.x Logging Level Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example configuration for setting the OptaPlanner logging level to debug in log4j.xml.

```xml
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

  <category name="org.optaplanner">
    <priority value="debug" />
  </category>

  ...
```

--------------------------------

### Exception Message Output Example

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a clear exception message output showing the invalid state.

```text
Exception in thread "main" java.lang.IllegalArgumentException: The fooSize (-5) of bar (myBar) must be positive.
    at ...
```

--------------------------------

### Initialize PlannerBenchmarkFactory

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Create a benchmark factory instance from an existing solver configuration XML file.

```java
PlannerBenchmarkFactory benchmarkFactory = PlannerBenchmarkFactory.createFromSolverConfigXmlResource(
        "org/optaplanner/examples/cloudbalancing/solver/cloudBalancingSolverConfig.xml");
```

--------------------------------

### Build and Run Maven Application

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Commands to package the application and execute the resulting JAR.

```bash
$ mvn clean install
...
$ java -jar target/hello-world-run.jar
```

--------------------------------

### JSON-B Score Serialization

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Examples of annotating solutions with HardSoftScore or BendableScore for JSON-B serialization.

```java
@PlanningSolution
public class CloudBalance {

    @PlanningScore
    private HardSoftScore score;

    ...
}
```

```java
@PlanningSolution
public class CloudBalance {

    @PlanningScore
    private BendableScore score;

    ...
}
```

--------------------------------

### Configure Java Module System for OptaPlanner

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Use the opens directive in module-info.java to allow OptaPlanner access to domain objects, constraints, and solver configurations.

```java
module org.optaplanner.cloudbalancing {
    requires org.optaplanner.core;
    ...

    opens org.optaplanner.examples.cloudbalancing; // Solver configuration
    opens org.optaplanner.examples.cloudbalancing.domain; // Domain classes
    opens org.optaplanner.examples.cloudbalancing.score; // Constraints
    ...
}
```

--------------------------------

### Execute the OptaPlanner Solver

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Demonstrates loading a problem, invoking the solver, and visualizing the resulting solution.

```java
        // Load the problem
        TimeTable problem = generateDemoData();

        // Solve the problem
        Solver<TimeTable> solver = solverFactory.buildSolver();
        TimeTable solution = solver.solve(problem);

        // Visualize the solution
        printTimetable(solution);
```

--------------------------------

### Implement hashCode for custom moves

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a hashCode implementation for a custom move class.

```java
@Override
    public int hashCode() {
        return new HashCodeBuilder()
                .append(cloudProcess)
                .append(toCloudComputer)
                .toHashCode();
    }
```

--------------------------------

### Compose unionMoveSelector

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of nesting entity, value, and move selectors within a unionMoveSelector.

```xml
    <unionMoveSelector>
      <changeMoveSelector>
        <entitySelector>
          ...
        </entitySelector>
        <valueSelector>
          ...
        </valueSelector>
        ...
      </changeMoveSelector>
      <swapMoveSelector>
        ...
      </swapMoveSelector>
    </unionMoveSelector>
```

--------------------------------

### Build PlannerBenchmark from Freemarker Template

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Initialize a benchmark factory using a Freemarker XML resource.

```java
        PlannerBenchmarkFactory benchmarkFactory = PlannerBenchmarkFactory.createFromFreemarkerXmlResource(
                "org/optaplanner/examples/cloudbalancing/optional/benchmark/cloudBalancingBenchmarkConfigTemplate.xml.ftl");
        PlannerBenchmark benchmark = benchmarkFactory.buildPlannerBenchmark();
```

--------------------------------

### Configure Gradle build.gradle for OptaPlanner

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Sets up the Java application environment, imports the OptaPlanner BOM, and specifies dependencies for core, testing, and logging.

```groovy
plugins {
    id "java"
    id "application"
}

def optaplannerVersion = "9.44.0.Final"
def logbackVersion = "1.2.9"

group = "org.acme"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
    implementation platform("org.optaplanner:optaplanner-bom:${optaplannerVersion}")
    implementation "org.optaplanner:optaplanner-core"
    testImplementation "org.optaplanner:optaplanner-test"

    runtimeOnly "ch.qos.logback:logback-classic:${logbackVersion}"
}

java {
    sourceCompatibility = JavaVersion.VERSION_11
    targetCompatibility = JavaVersion.VERSION_11
}

compileJava {
    options.encoding = "UTF-8"
    options.compilerArgs << "-parameters"
}

compileTestJava {
    options.encoding = "UTF-8"
}

application {
    mainClass = "org.acme.schooltimetabling.TimeTableApp"
}

test {
    // Log the test execution results.
    testLogging {
        events "passed", "skipped", "failed"
    }
}
```

--------------------------------

### Configure Local Search changeMoveSelector

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of configuring a changeMoveSelector within a localSearch block.

```xml
  <localSearch>
    <changeMoveSelector/>
    ...
  </localSearch>
```

--------------------------------

### Define chained planning entity

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a chained planning entity class structure.

```java
@PlanningEntity
public class Customer ... {
```

--------------------------------

### Implement EasyScoreCalculator logic

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of a score calculation loop for the N-Queens problem.

```java
        int score = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i + 1; j < n; j++) {
                Queen leftQueen = queenList.get(i);
                Queen rightQueen = queenList.get(j);
                if (leftQueen.getRow() != null && rightQueen.getRow() != null) {
                    if (leftQueen.getRowIndex() == rightQueen.getRowIndex()) {
                        score--;
                    }
                    if (leftQueen.getAscendingDiagonalIndex() == rightQueen.getAscendingDiagonalIndex()) {
                        score--;
                    }
                    if (leftQueen.getDescendingDiagonalIndex() == rightQueen.getDescendingDiagonalIndex()) {
                        score--;
                    }
                }
            }
        }
        return SimpleScore.valueOf(score);
    }

}
```

--------------------------------

### Configure MoveIteratorFactory in XML

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

XML configuration for MoveIteratorFactory, supporting both simple and advanced setups.

```xml
    <moveIteratorFactory>
      <moveIteratorFactoryClass>...</moveIteratorFactoryClass>
    </moveIteratorFactory>
```

```xml
    <moveIteratorFactory>
      ... <!-- Normal moveSelector properties -->
      <moveIteratorFactoryClass>...</moveIteratorFactoryClass>
      <moveIteratorFactoryCustomProperties>
        ...<!-- Custom properties -->
      </moveIteratorFactoryCustomProperties>
    </moveIteratorFactory>
```

--------------------------------

### Configure MoveListFactory in XML

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

XML configuration for MoveListFactory, supporting both simple and advanced setups.

```xml
    <moveListFactory>
      <moveListFactoryClass>org.optaplanner.examples.cloudbalancing.optional.solver.move.CloudComputerChangeMoveFactory</moveListFactoryClass>
    </moveListFactory>
```

```xml
    <moveListFactory>
      ... <!-- Normal moveSelector properties -->
      <moveListFactoryClass>org.optaplanner.examples.cloudbalancing.optional.solver.move.CloudComputerChangeMoveFactory</moveListFactoryClass>
      <moveListFactoryCustomProperties>
        ...<!-- Custom properties -->
      </moveListFactoryCustomProperties>
    </moveListFactory>
```

--------------------------------

### Configure and run advanced benchmark from XML

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Builds a benchmark factory from a classpath resource and executes the benchmark.

```java
PlannerBenchmarkFactory benchmarkFactory = PlannerBenchmarkFactory.createFromXmlResource(
        "org/optaplanner/examples/cloudbalancing/benchmark/cloudBalancingBenchmarkConfig.xml");
PlannerBenchmark benchmark = benchmarkFactory.buildPlannerBenchmark();
benchmark.benchmarkAndShowReportInBrowser();
```

--------------------------------

### Combine Tabu Types

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of combining multiple tabu types in a single acceptor configuration.

```xml
    <acceptor>
      <entityTabuSize>7</entityTabuSize>
      <valueTabuSize>3</valueTabuSize>
    </acceptor>
```

--------------------------------

### Configure OptaPlanner logging

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Adjust the logback.xml file to change the logging level for the org.optaplanner package.

```xml
  <logger name="org.optaplanner" level="debug"/>
```

--------------------------------

### Implement Customer Nearby Distance Meter

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of the NearbyDistanceMeter for a vehicle routing problem.

```java
public class CustomerNearbyDistanceMeter implements NearbyDistanceMeter<Customer, LocationAware> {

    public double getNearbyDistance(Customer origin, LocationAware destination) {
        return origin.getDistanceTo(destination);
    }

}
```

--------------------------------

### Create an uninitialized CourseSchedule solution

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Initializes a course schedule by creating lecture instances with null planning variables for periods and rooms.

```java
        private void createLectureList(CourseSchedule schedule) {
            List<Course> courseList = schedule.getCourseList();
            List<Lecture> lectureList = new ArrayList<Lecture>(courseList.size());
            long id = 0L;
            for (Course course : courseList) {
                for (int i = 0; i < course.getLectureSize(); i++) {
                    Lecture lecture = new Lecture();
                    lecture.setId(id);
                    id++;
                    lecture.setCourse(course);
                    lecture.setLectureIndexInCourse(i);
                    // Notice that we leave the PlanningVariable properties (period and room) on null
                    lectureList.add(lecture);
                }
            }
            schedule.setLectureList(lectureList);
        }
```

--------------------------------

### Custom VariableListener Definition

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a planning variable definition that would be monitored by a custom VariableListener.

```java
    @PlanningVariable(...)
    public Standstill getPreviousStandstill() {
        return previousStandstill;
    }
```

--------------------------------

### Defining a horizontal conflict constraint

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of a constraint stream that penalizes horizontal conflicts between queens.

```java
    protected Constraint horizontalConflict(ConstraintFactory factory) {
        return factory
                .forEachUniquePair(Queen.class, equal(Queen::getRowIndex))
                .penalize(SimpleScore.ONE)
                .asConstraint("Horizontal conflict");
    }
```

--------------------------------

### Template Solver Configuration

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Demonstrates creating a template SolverConfig for reuse across multiple user requests.

```java
    private SolverConfig template;

    public void init() {
        template = SolverConfig.createFromXmlResource(
                "org/optaplanner/examples/nqueens/solver/nqueensSolverConfig.xml");
        template.setTerminationConfig(new TerminationConfig());
    }
```

--------------------------------

### Implement TimeTableApp class

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

The TimeTableApp class initializes the solver with specific constraints and termination limits, generates demo data, and executes the solving process.

```java
package org.acme.schooltimetabling;

import java.time.DayOfWeek;
import java.time.Duration;
import java.time.LocalTime;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.acme.schooltimetabling.domain.Lesson;
import org.acme.schooltimetabling.domain.Room;
import org.acme.schooltimetabling.domain.TimeTable;
import org.acme.schooltimetabling.domain.Timeslot;
import org.acme.schooltimetabling.solver.TimeTableConstraintProvider;
import org.optaplanner.core.api.solver.Solver;
import org.optaplanner.core.api.solver.SolverFactory;
import org.optaplanner.core.config.solver.SolverConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TimeTableApp {

    private static final Logger LOGGER = LoggerFactory.getLogger(TimeTableApp.class);

    public static void main(String[] args) {
        SolverFactory<TimeTable> solverFactory = SolverFactory.create(new SolverConfig()
                .withSolutionClass(TimeTable.class)
                .withEntityClasses(Lesson.class)
                .withConstraintProviderClass(TimeTableConstraintProvider.class)
                // The solver runs only for 5 seconds on this small dataset.
                // It's recommended to run for at least 5 minutes ("5m") otherwise.
                .withTerminationSpentLimit(Duration.ofSeconds(5)));

        // Load the problem
        TimeTable problem = generateDemoData();

        // Solve the problem
        Solver<TimeTable> solver = solverFactory.buildSolver();
        TimeTable solution = solver.solve(problem);

        // Visualize the solution
        printTimetable(solution);
    }

    public static TimeTable generateDemoData() {
        List<Timeslot> timeslotList = new ArrayList<>(10);
        timeslotList.add(new Timeslot(DayOfWeek.MONDAY, LocalTime.of(8, 30), LocalTime.of(9, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.MONDAY, LocalTime.of(9, 30), LocalTime.of(10, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.MONDAY, LocalTime.of(10, 30), LocalTime.of(11, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.MONDAY, LocalTime.of(13, 30), LocalTime.of(14, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.MONDAY, LocalTime.of(14, 30), LocalTime.of(15, 30)));

        timeslotList.add(new Timeslot(DayOfWeek.TUESDAY, LocalTime.of(8, 30), LocalTime.of(9, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.TUESDAY, LocalTime.of(9, 30), LocalTime.of(10, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.TUESDAY, LocalTime.of(10, 30), LocalTime.of(11, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.TUESDAY, LocalTime.of(13, 30), LocalTime.of(14, 30)));
        timeslotList.add(new Timeslot(DayOfWeek.TUESDAY, LocalTime.of(14, 30), LocalTime.of(15, 30)));

        List<Room> roomList = new ArrayList<>(3);
        roomList.add(new Room("Room A"));
        roomList.add(new Room("Room B"));
        roomList.add(new Room("Room C"));

        List<Lesson> lessonList = new ArrayList<>();
        long id = 0;
        lessonList.add(new Lesson(id++, "Math", "A. Turing", "9th grade"));
        lessonList.add(new Lesson(id++, "Math", "A. Turing", "9th grade"));
        lessonList.add(new Lesson(id++, "Physics", "M. Curie", "9th grade"));
        lessonList.add(new Lesson(id++, "Chemistry", "M. Curie", "9th grade"));
        lessonList.add(new Lesson(id++, "Biology", "C. Darwin", "9th grade"));
        lessonList.add(new Lesson(id++, "History", "I. Jones", "9th grade"));
        lessonList.add(new Lesson(id++, "English", "I. Jones", "9th grade"));
        lessonList.add(new Lesson(id++, "English", "I. Jones", "9th grade"));
        lessonList.add(new Lesson(id++, "Spanish", "P. Cruz", "9th grade"));
        lessonList.add(new Lesson(id++, "Spanish", "P. Cruz", "9th grade"));
```

--------------------------------

### Enable Benchmark Output Solution

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Enables writing the best solution of each benchmark run to the benchmark directory.

```xml
    <problemBenchmarks>
      ...
      <writeOutputSolutionEnabled>true</writeOutputSolutionEnabled>
      ...
    </problemBenchmarks>
```

--------------------------------

### Initializing ConstraintVerifier

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Shows how to instantiate the ConstraintVerifier for a specific constraint provider.

```java
    private ConstraintVerifier<NQueensConstraintProvider, NQueens> constraintVerifier
            = ConstraintVerifier.build(new NQueensConstraintProvider(), NQueens.class, Queen.class);
```

--------------------------------

### Custom Selection Filter Implementation

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example implementation of a SelectionFilter to discard moves that swap lectures of the same course.

```java
public class DifferentCourseSwapMoveFilter implements SelectionFilter<CourseSchedule, SwapMove> {

    @Override
    public boolean accept(ScoreDirector<CourseSchedule> scoreDirector, SwapMove move) {
        Lecture leftLecture = (Lecture) move.getLeftEntity();
        Lecture rightLecture = (Lecture) move.getRightEntity();
        return !leftLecture.getCourse().equals(rightLecture.getCourse());
    }
```

--------------------------------

### Create SolverFactory from XML

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Builds a Solver instance using a configuration file located on the classpath.

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

--------------------------------

### Build PlannerBenchmark with Preloaded Datasets

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Pass preloaded datasets directly to the buildPlannerBenchmark method when working with database-stored data.

```java
        PlannerBenchmark plannerBenchmark = benchmarkFactory.buildPlannerBenchmark(dataset1, dataset2, dataset3);
```

--------------------------------

### Define Rules for Testing

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example DRL structure for rules intended to be validated by the unit testing harness.

```DRL
global HardSoftScoreHolder scoreHolder;

rule "requiredCpuPowerTotal"
    when
        ...
    then
        scoreHolder.addHardConstraintMatch(...);
end

...

rule "computerCost"
    when
        ...
    then
        scoreHolder.addSoftConstraintMatch(...);
end
```

--------------------------------

### Testing multiple constraints together

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of verifying the total score of a constraint provider against a set of facts.

```java
    @Test
    public void givenFactsMultipleConstraints() {
        Queen queen1 = new Queen(0, row1, column1);
        Queen queen2 = new Queen(1, row2, column2);
        Queen queen3 = new Queen(2, row3, column3);
        constraintVerifier.verifyThat()
                .given(queen1, queen2, queen3)
                .scores(SimpleScore.of(-3));
    }
```

--------------------------------

### Configure Maven pom.xml for OptaPlanner

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Includes the required Spring Boot and OptaPlanner dependencies for a school timetabling project.

```xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.0.7</version>
    </parent>

    <groupId>org.acme</groupId>
    <artifactId>optaplanner-spring-boot-school-timetabling-quickstart</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <java.version>11</java.version>
        <version.org.optaplanner>9.44.0.Final</version.org.optaplanner>
    </properties>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.optaplanner</groupId>
                <artifactId>optaplanner-bom</artifactId>
                <version>${version.org.optaplanner}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.optaplanner</groupId>
            <artifactId>optaplanner-spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.optaplanner</groupId>
            <artifactId>optaplanner-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>
```

--------------------------------

### Initialize SolverFactory

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Configures the solver with solution, entity, and constraint provider classes, including a termination limit.

```java
SolverFactory<TimeTable> solverFactory = SolverFactory.create(new SolverConfig()
        .withSolutionClass(TimeTable.class)
        .withEntityClasses(Lesson.class)
        .withConstraintProviderClass(TimeTableConstraintProvider.class)
        // The solver runs only for 5 seconds on this small dataset.
        // It's recommended to run for at least 5 minutes ("5m") otherwise.
        .withTerminationSpentLimit(Duration.ofSeconds(5)));
```

--------------------------------

### Configuring Score in Solution Class

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Example of annotating a score field within a planning solution class.

```java
@PlanningSolution
public class CloudBalance {
    ...

    @PlanningScore
    private HardSoftScore score;

}
```

--------------------------------

### Example REST service response

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

The expected JSON response from the solver containing the assigned timeslots and rooms.

```json
HTTP/1.1 200
Content-Type: application/json
...

{"timeslotList":...,"roomList":...,"lessonList":[{"id":1,"subject":"Math","teacher":"A. Turing","studentGroup":"9th grade","timeslot":{"dayOfWeek":"MONDAY","startTime":"08:30:00","endTime":"09:30:00"},"room":{"name":"Room A"}},{"id":2,"subject":"Chemistry","teacher":"M. Curie","studentGroup":"9th grade","timeslot":{"dayOfWeek":"MONDAY","startTime":"09:30:00","endTime":"10:30:00"},"room":{"name":"Room A"}},{"id":3,"subject":"French","teacher":"M. Curie","studentGroup":"10th grade","timeslot":{"dayOfWeek":"MONDAY","startTime":"08:30:00","endTime":"09:30:00"},"room":{"name":"Room B"}},{"id":4,"subject":"History","teacher":"I. Jones","studentGroup":"10th grade","timeslot":{"dayOfWeek":"MONDAY","startTime":"09:30:00","endTime":"10:30:00"},"room":{"name":"Room B"}}],"score":"0hard/0soft"}
```

--------------------------------

### Configure Solver via Java API

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Demonstrates creating a solver instance from a template and overriding termination limits programmatically.

```java
// Called concurrently from different threads
    public void userRequest(..., long userInput) {
        SolverConfig solverConfig = new SolverConfig(template); // Copy it
        solverConfig.getTerminationConfig().setMinutesSpentLimit(userInput);
        SolverFactory<NQueens> solverFactory = SolverFactory.create(solverConfig);
        Solver<NQueens> solver = solverFactory.buildSolver();
        ...
    }
```

--------------------------------

### Configure Matrix Benchmarking with Freemarker

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Use Freemarker loops to generate multiple solver configurations within a single benchmark XML file.

```xml
<plannerBenchmark xmlns="https://www.optaplanner.org/xsd/benchmark" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://www.optaplanner.org/xsd/benchmark https://www.optaplanner.org/xsd/benchmark/benchmark.xsd">
  ...
  <inheritedSolverBenchmark>
    ...
  </inheritedSolverBenchmark>

<#list [5, 7, 11, 13] as entityTabuSize>
<#list [500, 1000, 2000] as acceptedCountLimit>
  <solverBenchmark>
    <name>Tabu Search entityTabuSize ${entityTabuSize} acceptedCountLimit ${acceptedCountLimit}</name>
    <solver>
      <localSearch>
        <unionMoveSelector>
          <changeMoveSelector/>
          <swapMoveSelector/>
        </unionMoveSelector>
        <acceptor>
          <entityTabuSize>${entityTabuSize}</entityTabuSize>
        </acceptor>
        <forager>
          <acceptedCountLimit>${acceptedCountLimit}</acceptedCountLimit>
        </forager>
      </localSearch>
    </solver>
  </solverBenchmark>
</#list>
</#list>
</plannerBenchmark>
```

--------------------------------

### Create an uninitialized NQueens solution

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

Initializes an NQueens problem instance by setting up columns, rows, and a list of queens with null planning variables.

```java
    private NQueens createNQueens(int n) {
        NQueens nQueens = new NQueens();
        nQueens.setId(0L);
        nQueens.setN(n);
        nQueens.setColumnList(createColumnList(nQueens));
        nQueens.setRowList(createRowList(nQueens));
        nQueens.setQueenList(createQueenList(nQueens));
        return nQueens;
    }

    private List<Queen> createQueenList(NQueens nQueens) {
        int n = nQueens.getN();
        List<Queen> queenList = new ArrayList<Queen>(n);
        long id = 0L;
        for (Column column : nQueens.getColumnList()) {
            Queen queen = new Queen();
            queen.setId(id);
            id++;
            queen.setColumn(column);
            // Notice that we leave the PlanningVariable properties on null
            queenList.add(queen);
        }
        return queenList;
    }
```

--------------------------------

### Implement a Domicile Anchor

Source: https://docs.optaplanner.org/9.44.0.Final/optaplanner-docs/html_single/index.html

The anchor class implements the Standstill interface to serve as the starting point for a chain.

```java
public class Domicile ... implements Standstill {
    ...

    public City getCity() {...}

}
```
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