11:26:50.394 [main] INFO  o.d.p.core.solver.DefaultSolver - Solving started: time spend (187), score (null), new best score (null), random seed (0).

Exception in thread "main" java.lang.IllegalStateException: The selectionOrder (DECREASING_DIFFICULTY) can not be used on a PlanningEntity (com.swa.planner.domain.CloudProcess) that has no support for difficulty sorting. Check the @PlanningEntity annotation.

at org.drools.planner.core.heuristic.selector.entity.PlanningEntitySelector.validate(PlanningEntitySelector.java:53)

at org.drools.planner.core.heuristic.selector.entity.PlanningEntitySelector.phaseStarted(PlanningEntitySelector.java:45)

at org.drools.planner.core.constructionheuristic.greedyFit.selector.GreedyPlanningEntitySelector.phaseStarted(GreedyPlanningEntitySelector.java:41)

at org.drools.planner.core.constructionheuristic.greedyFit.DefaultGreedyFitSolverPhase.phaseStarted(DefaultGreedyFitSolverPhase.java:111)

at org.drools.planner.core.constructionheuristic.greedyFit.DefaultGreedyFitSolverPhase.solve(DefaultGreedyFitSolverPhase.java:57)

at org.drools.planner.core.solver.DefaultSolver.runSolverPhases(DefaultSolver.java:190)

at org.drools.planner.core.solver.DefaultSolver.solve(DefaultSolver.java:155)

at com.swa.planner.domain.CloudTest.main(CloudTest.java:51)

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I know why it is happening though (at least i think so), but will I have to implement the comparator to every planner I do or is there any other way to make it work?

I'm reproducing the example from the guide, when it passes the drools rules it gives that message. I didn't implement CloudComputerStrengthComparator neither CloudProcessDifficultyComparator, will I have to implement those so this example works?