[rules-users] Selective TSP?

[Geoffrey De Smet]

Op 20-03-13 01:34, rengana schreef:
> Hi,
>
> i'm evaluating Drools Planner as a solver for a "normal" OP problem but i
> can't find any example of drools usage on problems with partial set as a
> feasible solution, all drools examples and use cases seems to always try to
> plan every object even if that makes the solution unfeasible.
>
> I was able to model a OP problem using a modified version of the vehicle
> routing example using two vehicles, one for containing the customers visited
> (real solution) and a second vehicle for containing customers not visited.
> It works OK but this approach seems very dirty...
That's the way to go for now.

In the future we might be able support PlanningVariable(nullable= true, 
chained = true),
which would do what you want. There are some technical challenges for this.
Feel free to open a jira for it
   https://issues.jboss.org/browse/PLANNER
>
> Doesn't Drools Planner support a partial set solution that is feasible but
> doesn't have to contain all problem facts? Maybe a parameter to allow
> partial set solutions, and if so, be able to define the minimal problem
> facts needed to consider a posible solution.
>
> I was expecting that at least in the contruction phase the planner found
> some feasible solutions, since each step it is putting one element in the
> solution and then evaluating score, but found that the best solution passed
> to local seach isn't the best feasible solution of the contruction phase but
> always a unfeasible solution because somehow it's forcing to contains all
> problem facts.
If you use the approach mentioned above, it should try to put it in the 
Dummy vehicle as much as in the Real vehicle.

Your score rules should ignore the distance cost for the Dummy vehicle.
But you 'll also need an incentive to add cities to the Real vehicle,
otherwise it's going to put all the cities in the Dummy vehicle.

>
> Is this correct?
>
>
> Best regards,
> Rui
>
>
>
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