Hey,

Thank you James for your response.
I manage to solve a 324 tasks for 71 candidate technicians in 11 periods in less than 10 minutes.
I did not do much of optimization yet, as I need to look into that part. My knowledge about selectors and tabu-searches and heuristics is still far to limited.
The main effort I made is enhancing the algorithm to give a weight to the planning-enitities (Tasks) and technicians.
It did not seem to influence the solve-time that much, though it had major impact on the final score.
I have no idea why solving sometimes stops before 3600 seconds if hard-score is less than 0.

This is my termination config:

<termination>
<maximumSecondsSpend>3600</maximumSecondsSpend>
<scoreAttained>0hard/-999999soft</scoreAttained>
</termination>

But as POC (proof of concept) I guess I achieved my goal.

One unanswered question from my previous mail:

While rules are running: why do I get planningentities with uninitialized planningvariables (null)?

If "Task" is the planningentity and period is a planningvariable I need to put:

$task : Task(period != null, ... whatever)

Else the rule is executed with period is null, which results in all sorts of trouble, especially when using this planning variable in 'not equals' comparison.

Example of such rule which needs not-null checking:

rule "tasksInSameJobMustBeInSamePeriod"
    when
        $taskA : Task(period!=null, $id : id, $jobId : jobId, $periodId : periodId )
        $taskB : Task(period!=null, id > $id, jobId == $jobId, periodId != $periodId )
    then
        insertLogical(new IntConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $taskA, $taskB));
end

Without the (period!=null you get exceptions thrown complaining about constraints in excess.

Any ideas on why this is needed and if it is possible to never get nulls as planningvariable in the rules?

Regards,

Michiel

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From: James Owen - North Texas <jco@kbsc.com>
To: Michiel Vermandel <mvermand@yahoo.com>; Rules Users List <rules-users@lists.jboss.org>
Sent: Thursday, September 6, 2012 4:30 PM
Subject: Re: [rules-users] Best model for planning? technicians, airplanes and shifts => insertLogical problems

Greetings:

I started at the beginning of this thread and followed along (skipping only a one or two emails) and I was surprised that along the way that the problem grew and grew. There is an excellent discussion of this very situation in the seminal book on expert systems by Girratano and Riley (about chapter 5 or 6) on pattern matching wherein they discuss this very problem with matching multiple patterns of objects. When pattern matching it does matter the order in which you match the objects and their attributes because of the combinatorial explosion. You have only so much memory with which to work and, sooner or later, you will run out of memory.

You can't just throw all of the objects into a bucket willy-nilly and hope for the best results. The returned error may or may not be the one that you thought that it would be. 500 planes or 1,000 planes matched against multiple tasks matched against 12 months matched against multiple weeks matched against multiple shifts matched against … Well, you get the idea. As the list expands, the possibilities expand by the number of possibilities against which it can be matched. The project has to be architected and broken up into proper "chunks" so that it can be digested properly. You don't eat a steak nor an apple in one bite. You take it one bite at a time and chew it slowly and carefully. So it is with a large problem.

Even virtual memory is limited and will die out, as I have seen it done with benchmarks and the WaltzDB benchmark when programmed poorly. When one more item is added to the problem space you must remember that the memory required expands exponentially ever upwards so it is always best to keep the requirements small at all times and move from small sets to small sets, even when you have GigaBytes of RAM these days. Even later when we have TeraBytes, good programming will still be required for good results.

BTW, it seems that the God Father of benchmarks, Dr. Daniel Miranker (formerly of CMU and now at UT Austin) will be speaking at Intellifest 2012 this year. Visit http://www.IntelliFest.org for more details as they develop. They probably have a gathering of some of the best minds of AI this year if anyone would care to attend. Also, if anyone is looking for employment, they are planning on having recruiters there as well.

Shalom

jco

On Sep 3, 2012, at 7:31 AM, Michiel Vermandel wrote:

Ok,

I changed periodId > $periodId back into periodId != $periodId as I already discovered that this change resulted in invalid solutions.
Though, then I was back to the exception.

I now made another change which seems to be the solution... I think... I hope
Though, I do not understand the solution myself for 100%

What I did was testing if period is not null:

rule "tasksInSameJobMustBeInSamePeriod"
    when
        $taskA : MaintenanceTask(period!=null, $id : id, $jobId : jobId, $periodId : periodId )
        $taskB : MaintenanceTask(period!=null, id > $id, jobId == $jobId, periodId != $periodId )
    then
        insertLogical(new IntConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $taskA, $taskB));
end

I just tried that because all the sudden I tought checking null != null might not be such a good idea.
I now get the right combinations.

Can you please tell me if this is a correct change?

Once again one of my earlier questions arises: why is a rule tested upon an entity before the planning variables are set?
Or am I wrong here?

Thanks,

Michiel

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From: Geoffrey De Smet <ge0ffrey.spam@gmail.com>
To: Rules Users List <rules-users@lists.jboss.org>
Sent: Monday, September 3, 2012 2:15 PM
Subject: Re: [rules-users] Best model for planning? technicians, airplanes and shifts => insertLogical problems
Op 03-09-12 13:59, Michiel Vermandel schreef:

Hi,

I'm not keen on spending time on a temp solution if I cannot estimate - at this time - how much time it will take me to build it correctly afterwards.
Budgets are limited... (as with anyone I guess :-)
Once again, it gives me a bad feeling that such a simple setup is giving me such a hard to solve issue.

Incremental score calculation isn't a simple concept nor easy to implement.
But I agree that Drools and Planner should shield you from that complexity and take the heat there.
Planner already has extensive support to detect score corruption in incremental score calculation,
and Drools's compensation action looks promising to take greatly simply the complexity to the user.

I had thought that - given the project is only a very few classes - it would be peanuts for you or any other expert to pinpoint what I'm doing wrong.

I didn't have the time to read all the classes in detail, just glimpsed over them.

Non the less...

I tried to have a look again to a number of examples and I changed my rules, with a positive result!
I seem to get the correct solution. But... I do not know if my changes are valid.
I mean, is it possible that I threw a number of possible solutions away?
Maybe this will not show right now but will have it's effect when numbers grow and possible solutions shrink.

So what I did is going from

rule "tasksInSameJobMustBeInSamePeriod"
    when
        $taskA : MaintenanceTask($id : id, $jobId : jobId, $periodId : periodId )
        MaintenanceTask(id != $id, jobId == $jobId, periodId != $periodId )     // <============   a != $a
    then
        System.out.println("r3: " + $taskA );
        insertLogical(new IntConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $taskA));
end

to

rule "tasksInSameJobMustBeInSamePeriod"
    when
        $taskA : MaintenanceTask($id : id, $jobId : jobId, $periodId : periodId )

$taskB:

        MaintenanceTask(id > $id,

Good, because if you count the combination task5-task7, you don't want to count the combination task7-task5 too.

jobId == $jobId, periodId > $periodId )    // <================ a > $a

Bad, keep this on periodId != $periodId (or even period != $period)

    then
        System.out.println("r3: " + $taskA );
        insertLogical(new IntConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $taskA));

Add $taskB too:
insertLogical(new IntConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $taskA, $taskB));

end

Can you please tell me if this is THE solution or a dangerous move that works out now but will give issues when numbers grow?

The id > $id change is good, the periodId != $periodId isn't.

The above fixes could explain score corruption. You no longer get any exceptions in environmentMode DEBUG or TRACE?

Keep looking at the examples: they work and they scale.
Keep providing feedback as to the pain points too of course.

Hope that helps.
Thanks a lot.

Michiel

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From: Geoffrey De Smet <ge0ffrey.spam@gmail.com>
To: Michiel Vermandel <mvermand@yahoo.com>; Rules Users List <rules-users@lists.jboss.org>
Sent: Monday, September 3, 2012 11:56 AM
Subject: Re: Best model for planning? technicians, airplanes and shifts => insertLogical problems
Op 03-09-12 11:30, Michiel Vermandel schreef:

I did not really start on one example. I have scrolled through several to try to figure out how to do it, then started from scratch for the POJO's and Rules.

The config file was copies from one of the examples because it contained too many things that were hard to get right in the beginning.

I know that is a risk but I needed to start somewhere.

I am thinking how to standardize the getting started with planner experience.
The cloud balance quick start is the example I pushing at the moment.
But for specific use case, it's better to start from an example that's similar to the user's use case.
The trouble is, it's often hard to see which example is similar and which is not.

3) What does "The workingMemory has 2 ConstraintOccurrence(s) in excess:" really mean?

    - Are the constraints there more than once?

No, it means that in a clean WorkingMemory, those 2 ConstraintOccurrences aren't there,
but in the incremental WorkingMemory, they are there.
So they are in excess: they should have been automatically retracted by the rule engine, but for some reason, they are not.

Read this section about incremental score calculation to understand why this complexity is needed:
http://docs.jboss.org/drools/release/5.4.0.Final/drools-planner-docs/html_single/index.html#incrementalScoreCalculation

If you just want to prove that a Planner POC works for now (especially if you're close to giving up),
just take a few minutes to switch to a simple Java score calculator for now:
   http://docs.jboss.org/drools/release/5.4.0.Final/drools-planner-docs/html_single/index.html#d0e3336
It will be _much_ slower especially when it scales out (but it should still be faster than anything you can invent yourself within reasonable time).
Once that works fine and you get a good result on your toy problem and you can scale out to 100+ jobs,
then switch back to drools to scale out to 10000+ jobs and follow the rest of this mail.

    - has this something to do with the equals and hashcode (which I did implement (see below))?

Likely. The equals/hashcode methods are used of all objects in the causes parameter.
It's a design issue in Planner that the planner entity's equals/hashcode() needs to be used for the ConstraintOccurrence's causes.
Compensation action

    About the compensation action: is it already available on 5.4.0 final? Should I try that?

The plumbing is there in Drools Expert, but in Planner there are no decent examples, supporting code or even complex experiments yet.
It's a minefield, probably best to stay out until I get it done or you have more Planner experience :/

4) I have been looking to the equals and hashcode, though found many examples that implement solutionEquals and solutionHashcode instead.

    Currently I implemented them like this:

    @Override
    public int hashCode() {
        return id.hashCode(); //(*)
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (id == null || !(o instanceof MaintenanceTask)) {
            return false;
        } else {
            MaintenanceTask other = (MaintenanceTask) o;
            return id.equals(other.id);
        }
    }

Looks good

(*) id is a String property which is passed into the entity object through the constructor and upon cloning it is passed from the clone source to the clone target:

        public MaintenanceTask clone() {
            System.out.println("Cloning task " + id);
            MaintenanceTask clone = new MaintenanceTask(job, id);
            clone.period = this.period;
            clone.technician = this.technician;
            return clone;
        }

Looks good.



I am still confused about:

    - Which ones do I need to implement (equals or solutionEquals, ...)?

because of this code:
https://github.com/droolsjbpm/drools-planner/blob/master/drools-planner-core/src/main/java/org/drools/planner/core/score/constraint/ConstraintOccurrence.java#L54
which is called by drools on insertLogical inserted objects (see drools expert manual on insertLogical)

    - Should an entity and a cloned entity have the same result for both equals and hashcode? (I guess so)

Yes, definitely.

    - Should only the entity objects have such implementations? (Planning variables are never cloned, right?)

It looks good. Only the entity's are cloned indeed during cloneSolution(): they are the only instances that change during planning.
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From: Geoffrey De Smet <ge0ffrey.spam@gmail.com>
To: Rules Users List <rules-users@lists.jboss.org>
Sent: Monday, September 3, 2012 10:44 AM
Subject: Re: [rules-users] Best model for planning? technicians, airplanes and shifts => insertLogical problems

Op 03-09-12 10:21, Michiel Vermandel schreef:
> Hi Geoffrey,
>
> Thanks for the support so far.
> I understand that you do not provide full support on this level.
> Though I have the feeling that this is really
> - a very basic solution setup
> - a beginners-mistake and since I'm looking into it now for about 3 days
> (since I started with planner) it seems to be not obvious to find for a
> beginner.
> So I was trying my luck in offering the code.
> It could be an opportunity to enrich the documentation ;-) ;-)

Good point, the score corruption problem is often a beginner problem and
it's a PITA. I 'll write some more docs about.

Do note that your 3 day implementation should be able to scale out to
10000 planes pretty easily, so hang in there :)
I fear you might have started copying from the wrong example nqueens (if
you did that) :/ Nurse rostering is a far more similar to this kind of
problem. I am not sure which example to promote in the docs: the nqueens
is simple enough to explain things on, but it's too simple to copy from
for real world stuff :/ Feedback welcome.

>
>
> Ok,
>
> 1) adding the $t2 results in the same sort of exception, only
> planningEntity seems different:
>
> with insertLogical(new
> UnweightedConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $t1,
> $t2));
>
> Exception in thread "main" java.lang.IllegalStateException: Score
> corruption: the workingScore (-2) is not the uncorruptedScore (0):
> The workingMemory has 2 ConstraintOccurrence(s) in excess:
> tasksInSameJobMustBeInSamePeriod/NEGATIVE_HARD:[Maintenance of
> Boeing 737 - PJ23.I#1 73111693, Maintenance of Boeing 737 - PJ23.I#2
> 427578167]
> tasksInSameJobMustBeInSamePeriod/NEGATIVE_HARD:[Maintenance of
> Boeing 737 - PJ23.I#2 427578167, Maintenance of Boeing 737 - PJ23.I#1
> 73111693]
> Check the score rules who created those ConstraintOccurrences. Verify
> that each ConstraintOccurrence's causes and weight is correct.
> at
> org.drools.planner.core.score.director.AbstractScoreDirector.assertWorkingScore(AbstractScoreDirector.java:101)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.decider.DefaultGreedyDecider.doMove(DefaultGreedyDecider.java:110)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.decider.DefaultGreedyDecider.decideNextStep(DefaultGreedyDecider.java:78)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.DefaultGreedyFitSolverPhase.solve(DefaultGreedyFitSolverPhase.java:63)
> at
> org.drools.planner.core.solver.DefaultSolver.runSolverPhases(DefaultSolver.java:183)
> at
> org.drools.planner.core.solver.DefaultSolver.solve(DefaultSolver.java:151)
> at
> be.axi.planner.domain.MaintenancePlanning.main(MaintenancePlanning.java:27)
>
> with insertLogical(new
> UnweightedConstraintOccurrence("tasksInSameJobMustBeInSamePeriod", $t1));
>
> Exception in thread "main" java.lang.IllegalStateException: Score
> corruption: the workingScore (-2) is not the uncorruptedScore (0):
> The workingMemory has 2 ConstraintOccurrence(s) in excess:
> tasksInSameJobMustBeInSamePeriod/NEGATIVE_HARD:[Maintenance of
> Airbus A350 - XJ34.I#2 778813475]
> tasksInSameJobMustBeInSamePeriod/NEGATIVE_HARD:[Maintenance of
> Airbus A350 - XJ34.I#0 225744121]
> Check the score rules who created those ConstraintOccurrences. Verify
> that each ConstraintOccurrence's causes and weight is correct.
> at
> org.drools.planner.core.score.director.AbstractScoreDirector.assertWorkingScore(AbstractScoreDirector.java:101)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.decider.DefaultGreedyDecider.doMove(DefaultGreedyDecider.java:110)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.decider.DefaultGreedyDecider.decideNextStep(DefaultGreedyDecider.java:78)
> at
> org.drools.planner.core.constructionheuristic.greedyFit.DefaultGreedyFitSolverPhase.solve(DefaultGreedyFitSolverPhase.java:63)
> at
> org.drools.planner.core.solver.DefaultSolver.runSolverPhases(DefaultSolver.java:183)
> at
> org.drools.planner.core.solver.DefaultSolver.solve(DefaultSolver.java:151)
> at
> be.axi.planner.domain.MaintenancePlanning.main(MaintenancePlanning.java:27)
>
>
> 2) You suggested to replace UnweightedConstraintOccurrence with
> IntConstraintOccurrence. I will.
> UnweightedConstraintOccurrence is used in the very basic Queens example
> though...

Yep, my mistake.

>
> 3) Where is the best place to read about what insertLogical and
> IntConstraintOccurrence really do?
> What is the purpose of the Cause -objects, which should be passed?
> => where is the best place to find explanation about this?
> (http://docs.jboss.org/drools/release/5.4.0.Final/drools-planner-docs/html_single/
> doesn't really enlighten me on that part)

Look for "insertLogical" in the Drools Expert guide:

http://docs.jboss.org/drools/release/5.4.0.Final/drools-expert-docs/html_single/index.html

When rules do an insertLogical of an object A, it's discarded if another
object B in the WorkingMemory equals object A (through equals() and
through hashcode()). Because the ConstraintOccurrences need to be unique
so they aren't discarded, they ruleId, constraintType and causes are
used for equals()/hashcode().

Future work: "compensation action"
Recently, drools introduced something called "compensation action",
which can probably replace the use insertLogical(ConstraintOccurrence)
and make the causes parameter obsolete.
It's also faster.
My first experiments look very promising, but I haven't got time yet to
experiment with it on all examples and make it easy for users to use.

It would allow us to do something like this in the then part of a rule:
hardAndSoftScoreHelper.addHardScore(-5);
or
hardAndSoftScoreHelper.addSoftScore(- $sum);
or
simpleScoreHelper.addScore(-7);

No need for causes, insertLogicals, no equals/hashcode() worries, much
more flexible, ...

4) Does your MaintenanceTask implement equals()/hashcode() other than
Object's original implementation?

>
> Thanks in advance.
>

yw

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