Uncaught exception: Solving failed while running mixed-vrp code

Question

I was looking into the code that I found on github as I was working on a similar project. This is the link: https://github.com/ge0ffrey/optaplanner-mixedvrp-experiment I tried running the same code and I was getting an IllegalStateException and the trace is as follows:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Solving failed.
    at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.done(SolverAndPersistenceFrame.java:381)
    at java.desktop/javax.swing.SwingWorker$5.run(SwingWorker.java:750)
    at java.desktop/javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:848)
    at java.desktop/sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
    at java.desktop/javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:858)
    at java.desktop/javax.swing.Timer.fireActionPerformed(Timer.java:311)
    at java.desktop/javax.swing.Timer$DoPostEvent.run(Timer.java:243)
    at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Caused by: java.lang.IllegalStateException: The entity (Visit-18) has a variable (previousStandstill) with value (Visit-25) which has a sourceVariableName variable (nextVisit) with a value (Visit-12) which is not null.
Verify the consistency of your input problem for that sourceVariableName variable.
    at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.insert(SingletonInverseVariableListener.java:74)
    at org.optaplanner.core.impl.domain.variable.inverserelation.SingletonInverseVariableListener.afterVariableChanged(SingletonInverseVariableListener.java:53)
    at org.optaplanner.core.impl.domain.variable.listener.support.VariableListenerSupport.triggerVariableListenersInNotificationQueues(VariableListenerSupport.java:214)
    at org.optaplanner.core.impl.score.director.AbstractScoreDirector.triggerVariableListeners(AbstractScoreDirector.java:295)
    at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:37)
    at org.optaplanner.core.impl.heuristic.move.AbstractMove.doMove(AbstractMove.java:31)
    at org.optaplanner.core.impl.heuristic.move.CompositeMove.doMove(CompositeMove.java:109)
    at org.optaplanner.core.impl.heuristic.move.CompositeMove.doMove(CompositeMove.java:38)
    at org.optaplanner.core.impl.score.director.AbstractScoreDirector.doAndProcessMove(AbstractScoreDirector.java:223)
    at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.doMove(LocalSearchDecider.java:133)
    at org.optaplanner.core.impl.localsearch.decider.LocalSearchDecider.decideNextStep(LocalSearchDecider.java:117)
    at org.optaplanner.core.impl.localsearch.DefaultLocalSearchPhase.solve(DefaultLocalSearchPhase.java:71)
    at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:99)
    at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:160)
    at org.optaplanner.examples.common.business.SolutionBusiness.solve(SolutionBusiness.java:344)
    at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.doInBackground(SolverAndPersistenceFrame.java:369)
    at java.desktop/javax.swing.SwingWorker$1.call(SwingWorker.java:304)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
    at java.desktop/javax.swing.SwingWorker.run(SwingWorker.java:343)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
    at java.base/java.lang.Thread.run(Thread.java:1623)

I tried debugging the code but couldn't find out why it's throwing this exception. Please help me out.

Answer 1

The clue is in the name, "experiment". It is a personal repo of one of the former OptaPlanner developers, and there are no guarantees that it is correct. In fact, it is most likely unfinished, and definitely obsolete.

To confirm that, the most recent commit to the repository (already 3 years ago) speaks of the score corruption and of the fact that it needs to be fixed. Meaning Geoffrey was aware of it, and did not fix it.

For that reason, I wouldn't base your work on this experimental piece of code, unless you are prepared to track down the score corruption Geoffrey did not.