Op 07-12-11 21:41, Patrik Dufresne schreef:

Hi all,

I'm trying to create rules to model my problem. So far, I didn't manage to create rules to make Drools converge to a solution because of score traps. I don't see any way to avoid it (as I'm not an expert with Drools). I can express the rule as follow : a senior employee should work before a less senior employee.

I've implement it as a hard constraint :

rule "hard-Seniority"

when

$employee : Employee()

$assignment : PlanifEventAssignment( $planifEmployee : employee )

What's does this $planifEmployee do?

not PlanifEventAssignment( employee == $employee )

eval(Helper.compareEmployee($employee, $planifEmployee) < 0)

then

insertLogical(new IntConstraintOccurrence("hard-Seniority",

ConstraintType.NEGATIVE_HARD,

1,

$employee, $assignment));

end

The function Helper.compareEmployee(e1, e2) return -1 if e1 is more senior then e2 (mostly based on hire date and other boolean fields).

On first sight, in Solution.getProblemFact() I would add these cached problem facts, for any 2 employees (but just once per combination):
new EmployeeRanking(higherRankedEmployee, lowerRankedEmployee, numberOfEmployeesInRankBetweenThem)

then you can do

rule "hard-Seniority"

when
         EmployeeRanking($higherRankedEmployee, $lowerRankedEmployee, $numberOfEmployeesInRankBetweenThem)
         PlanifEventAssignment(employee == $lowerRankedEmployee)
         PlanifEventAssignment(employee == $higherRankedEmployee)

then

insertLogical(new IntConstraintOccurrence("hard-Seniority",

ConstraintType.NEGATIVE_HARD,

$numberOfEmployeesInRankBetweenThem,

$employee, $assignment));

This way, the rule make sure a senior employee is working. But it's a score trap since, many moves are required to resolve the constraint. e.g:

PlanifEventAssignment1 = e2

PlanifEventAssignment2 = e3

PlanifEventAssignment3 = e4

PlanifEventAssignment4 = e5

e1 is not working. Multiple move are require to reach the best solution :

PlanifEventAssignment1 = e1

PlanifEventAssignment2 = e2

PlanifEventAssignment3 = e3

PlanifEventAssignment4 = e4

So I'm asking you. What is the best way to make Drools converge ? Do I need to change my rule, or should I create a BigMove ?

course grained moves will work mostly, but solving the score trap itself is a far better long-term solution (and it still allows you to add course grained moves later).

--
Patrik Dufresne


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-- 
With kind regards,
Geoffrey De Smet