NQueens application with 4 queens fails on solving the problem when exhaustiveSearch with type BRANCH_AND_BOUND is used. Logs report score corruption.
2015-05-22 09:06:25,873 [AWT-EventQueue-0] INFO Opened: data/nqueens/unsolved/4queens.xml
2015-05-22 09:06:27,275 [SwingWorker-pool-3-thread-1] INFO Solving started: time spent (10), best score (uninitialized/0), environment mode (FULL_ASSERT), random (JDK with seed 0).
2015-05-22 09:06:27,309 [SwingWorker-pool-3-thread-1] DEBUG ES step (0), time spent (44), treeId (0-0), best score (uninitialized/0), selected move count (4).
2015-05-22 09:06:27,331 [SwingWorker-pool-3-thread-1] DEBUG ES step (1), time spent (65), treeId (1-0), best score (uninitialized/0), selected move count (4).
2015-05-22 09:06:27,340 [SwingWorker-pool-3-thread-1] DEBUG ES step (2), time spent (75), treeId (2-3), best score (uninitialized/0), selected move count (4).
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: Solving failed.
at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.done(SolverAndPersistenceFrame.java:297)
at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)
at javax.swing.Timer.fireActionPerformed(Timer.java:312)
at javax.swing.Timer$DoPostEvent.run(Timer.java:244)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:312)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:745)
at java.awt.EventQueue.access$300(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:706)
at java.awt.EventQueue$3.run(EventQueue.java:704)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:715)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
Caused by: java.lang.IllegalStateException: The moveClass (class org.optaplanner.core.impl.heuristic.selector.move.generic.ChangeMove)'s move (col0@null => row1) probably has a corrupted undoMove (col0@null => null). Or maybe there are corrupted score rules.
Check the Move.createUndoMove(...) method of that Move class and enable EnvironmentMode FULL_ASSERT to fail-faster on corrupted score rules.
Score corruption: the lastCompletedStepScore (0) is not the undoScore (-1).
at org.optaplanner.core.impl.phase.scope.AbstractPhaseScope.assertExpectedUndoMoveScore(AbstractPhaseScope.java:140)
at org.optaplanner.core.impl.exhaustivesearch.decider.ExhaustiveSearchDecider.doMove(ExhaustiveSearchDecider.java:145)
at org.optaplanner.core.impl.exhaustivesearch.decider.ExhaustiveSearchDecider.expandNode(ExhaustiveSearchDecider.java:127)
at org.optaplanner.core.impl.exhaustivesearch.DefaultExhaustiveSearchPhase.solve(DefaultExhaustiveSearchPhase.java:104)
at org.optaplanner.core.impl.solver.DefaultSolver.runPhases(DefaultSolver.java:213)
at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:176)
at org.optaplanner.examples.common.business.SolutionBusiness.solve(SolutionBusiness.java:302)
at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.doInBackground(SolverAndPersistenceFrame.java:286)
at org.optaplanner.examples.common.swingui.SolverAndPersistenceFrame$SolveWorker.doInBackground(SolverAndPersistenceFrame.java:276)
at javax.swing.SwingWorker$1.call(SwingWorker.java:296)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at javax.swing.SwingWorker.run(SwingWorker.java:335)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)

Solver configuration is attached