Solution Partitioning failing - optaplanner

Question

I have implemented a solution partitioner for my planning problem. But when I now run the optimizer, it returns the following error:
Exception in thread "main" java.lang.IllegalStateException: The partition child thread with partIndex (1) has thrown an exception. Relayed here in the parent thread.
at org.optaplanner.core.impl.partitionedsearch.queue.PartitionQueue$PartitionQueueIterator.createUpcomingSelection(PartitionQueue.java:157)
at org.optaplanner.core.impl.partitionedsearch.queue.PartitionQueue$PartitionQueueIterator.createUpcomingSelection(PartitionQueue.java:121)
at org.optaplanner.core.impl.heuristic.selector.common.iterator.UpcomingSelectionIterator.hasNext(UpcomingSelectionIterator.java:42)
at org.optaplanner.core.impl.partitionedsearch.DefaultPartitionedSearchPhase.solve(DefaultPartitionedSearchPhase.java:131)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:191)
at com.paconsulting.Demo.main(PowerPeersDemo.java:137)
Caused by: java.lang.IllegalStateException: When lookUpEnabled (false) is disabled in the constructor, this method should not be called.
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.lookUpWorkingObject(AbstractScoreDirector.java:506)
at org.optaplanner.core.impl.heuristic.selector.move.generic.ChangeMove.rebase(ChangeMove.java:83)
at org.optaplanner.core.impl.heuristic.selector.move.generic.ChangeMove.rebase(ChangeMove.java:33)
at org.optaplanner.core.impl.localsearch.decider.MultiThreadedLocalSearchDecider.forageResult(MultiThreadedLocalSearchDecider.java:196)
at org.optaplanner.core.impl.localsearch.decider.MultiThreadedLocalSearchDecider.decideNextStep(MultiThreadedLocalSearchDecider.java:157)
at org.optaplanner.core.impl.localsearch.DefaultLocalSearchPhase.solve(DefaultLocalSearchPhase.java:70)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
at org.optaplanner.core.impl.partitionedsearch.PartitionSolver.solve(PartitionSolver.java:121)
at org.optaplanner.core.impl.partitionedsearch.DefaultPartitionedSearchPhase.lambda$solve$1(DefaultPartitionedSearchPhase.java:119)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
2019-03-21 21:47:41,705 [main] DEBUG PS step (1), time spent (1493), score (-249530hard/0soft), best score (-249530hard/0soft), picked move (part-0 {3886 variables changed}).
Exception in thread "main" java.lang.IllegalStateException: The partition child thread with partIndex (1) has thrown an exception. Relayed here in the parent thread.
at org.optaplanner.core.impl.partitionedsearch.queue.PartitionQueue$PartitionQueueIterator.createUpcomingSelection(PartitionQueue.java:157)
at org.optaplanner.core.impl.partitionedsearch.queue.PartitionQueue$PartitionQueueIterator.createUpcomingSelection(PartitionQueue.java:121)
at org.optaplanner.core.impl.heuristic.selector.common.iterator.UpcomingSelectionIterator.hasNext(UpcomingSelectionIterator.java:42)
at org.optaplanner.core.impl.partitionedsearch.DefaultPartitionedSearchPhase.solve(DefaultPartitionedSearchPhase.java:131)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:191)
at com.paconsulting.powerpeers.PowerPeersDemo.main(PowerPeersDemo.java:137)
Caused by: java.lang.IllegalStateException: When lookUpEnabled (false) is disabled in the constructor, this method should not be called.
at org.optaplanner.core.impl.score.director.AbstractScoreDirector.lookUpWorkingObject(AbstractScoreDirector.java:506)
at org.optaplanner.core.impl.heuristic.selector.move.generic.ChangeMove.rebase(ChangeMove.java:83)
at org.optaplanner.core.impl.heuristic.selector.move.generic.ChangeMove.rebase(ChangeMove.java:33)
at org.optaplanner.core.impl.localsearch.decider.MultiThreadedLocalSearchDecider.forageResult(MultiThreadedLocalSearchDecider.java:196)
at org.optaplanner.core.impl.localsearch.decider.MultiThreadedLocalSearchDecider.decideNextStep(MultiThreadedLocalSearchDecider.java:157)
at org.optaplanner.core.impl.localsearch.DefaultLocalSearchPhase.solve(DefaultLocalSearchPhase.java:70)
at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
at org.optaplanner.core.impl.partitionedsearch.PartitionSolver.solve(PartitionSolver.java:121)
at org.optaplanner.core.impl.partitionedsearch.DefaultPartitionedSearchPhase.lambda$solve$1(DefaultPartitionedSearchPhase.java:119)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
I do have implemented #PlanningId on all the relevant objects.
Running version 1.18 of OptaPlanner.

Answer 1

This is a bug, thank you for reporting:
Partitioned Search is incompatible with Multithreaded Incremental Solving in version 7.19 or lower. This was a gap in our test coverage.
Partitioned Search was implemented before Multithreaded Incremental Solving and the latter didn't take it into account here on AbstractScoreDirector:
public InnerScoreDirector<Solution_> createChildThreadScoreDirector(ChildThreadType childThreadType) {
if (childThreadType == ChildThreadType.PART_THREAD) {
AbstractScoreDirector<Solution_, Factory_> childThreadScoreDirector = (AbstractScoreDirector<Solution_, Factory_>)
scoreDirectorFactory.buildScoreDirector(false, constraintMatchEnabledPreference); // That false is lookUpEnabled
That false kills the ability to nest multithreaded solving under Partitioned Search.
I've created a jira issue and fixed it for 7.20 in this pull request.