[rules-users] Multiplying the count of each score rule [planner]

[Patrik Dufresne]

Hi Geoffrey,

Thanks for your opinion. I will try to implement what I call a
HardAndSoftPriorityScoreDefinition and give it back to the community. Where
is the best place to post a 'patch' ?

2011/12/19 Geoffrey De Smet <ge0ffrey.spam at gmail.com>

> **
>
>
> Op 14-12-11 18:40, Patrik Dufresne schreef:
>
>   Hi,
>
>  I'm still in process to model my planning problem and I have some
> difficulties in defining the correct weight of soft constraints. I have
> soft constraints with different priorities : C1, C2, C3, ..., Cn where C1
> are higher then C2. Currently, I've tried to set different weight for each
> of them : C1 get higher weight. But it's not sufficient since multiple C2
> may balance one C1. What I really need is to set the priority to every soft
> constraints.
>
>  Solution #1 :
> My first thought it to implement a new score definition
> (HardAndSoftPriorityScoreDefinition) having separate soft score for each
> priority. The rule may insert ConstraintOccurence by defining the weight
> and the priority. This solution seems elegant but require effort to
> implement the score definition, the score calculation, and other things I
> don't even know about.
>
> That is the perfect solution to your problem. Start by copy pasting DefaultHardAndSoftScoreDefinition
> and work your way from there.
> You'll need to create at least a ScoreDefinition, ScoreCalculator and
> Score.
>
> I've been thinking about adding such a "dynamic" score definition to
> planner's build-in scores,
> but so far every use case where the developers said they needed this, it
> turned out end-users meant it differently:
> when you break a 100 C2's, then it's better to break 1 C1 instead...
>
>
>  Solution #2 :
> The other solution is stated in the Drools Planner User Guide :
>
>   "Most use cases will also weigh their constraints differently, by
> multiplying the count of each score rule with its weight. For example in
> freight routing, you can make 5 broken "avoid crossroads" soft constraints
> count as much as 1 broken "avoid highways at rush hour" soft constraint.
> This allows your business analysts to easily tweak the score function as
> they see fit."
>
>    Even tough I don't know how to implement this, it's seems much easier
> to achieve since it's only a rule. Compare to solution #1, it's lack the
> support of soft constraints with same priority but different weights.
>
> That text describes plain-old weighting. Say C1 weights 100 and C2 weights
> 2, then you can break 50 C2's for every 1 broken C1.
>
> This is far easier and most of the time end-users actually mean this.
> Make exaggerated examples (1000 C2's broken vs 1 C1 broken) and make your
> end-users decide what they prefer. If they still prefer 1000 C2's broken,
> then you need #1.
>
> Tip: Sometimes, taking the square of a weight is a neat trick.
> In bin packing, say you got
> Solution A with 3 CPU and 3 CPU too little = 3² + 3² = 18
> and Solution B with 4 CPU and 2 CPU too little = 4² + 2² = 20
> So the second is worse even though they both miss 6 CPU.
>
>
>  What is your opinion about both solution.
>
>  Is one faster then the other ?
>
>  Is it hard to create a new score definition ?
>
>  Did anyone ever did this ?
>
>    --
> Patrik Dufresne
>
>
> _______________________________________________
> rules-users mailing listrules-users at lists.jboss.orghttps://lists.jboss.org/mailman/listinfo/rules-users
>
>
> --
> With kind regards,
> Geoffrey De Smet
>
>
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>


-- 
Patrik Dufresne
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