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

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(a)gmail.com <mailto:ge0ffrey.spam@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 list > rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/rules-users -- With kind regards, Geoffrey De Smet _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users -- Patrik Dufresne _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users