forEachUniquePair usage

[jerome1968]

Hello, I see in the quickstarts that constraints with forEachUniquePair use a Joiner, but in my case I do not need any join to be done. In the constraint below, I want to set that two specific visits must have to be assigned to the same carrier. In my solution, this constraint is violated with score 0 (though the constraint weight is 200). If a given visit1 is subject to the constraint, the other visit2 is known as the constraint parameter for visit1 (getParameter()). May be I missed something with the forEachUniquePair usage... Any advice?
Thank you.

protected Constraint uniqueCarrier(ConstraintFactory constraintFactory, String cstName) {
    return constraintFactory.forEachUniquePair(Visit.class)
            .filter((visit1, visit2) -> visit1.getOrderPart().subjectToConstraint(cstName) &&
                    visit2.getOrderPart().getId().equals(visit1.getOrderPart().getConstraint(cstName).getParameter()) &&
                    !visit1.getCarrier().getId().equals(visit2.getCarrier().getId())) // different carrier
            .penalizeLong(HardSoftLongScore.ONE_HARD,
                    (visit1,visit2) -> visit1.getOrderPart().getConstraint(cstName).getWeight())
            .asConstraint(cstName);
}

[TomCools]

Hi @jerome1968

Your constraint is a bit weird with the fact it takes a String to define if the visit is actually subject to the constraint.
I wouldn't do that as it hides some of the intent.

I would model this instead as:

• Visit
  • requiresSameCarrierAs(List)

Changing your domain like this, makes the whole thing a lot easier.

[jerome1968]

Thank you @TomCools for your response.
Indeed, I am doing some experiments with a very lean data model putting most of the things in a fact base and accessing these data in constraint scoring implementation itself using "constrained planning variables". This allowes me to log in the solution which constraints are applied to each planning variable.

But you are right, because this kind of relationship is built at preprocessing, It is more efficient for score computing to enrich the planning entities the way you mentionned.

Before closing this discussion, let me ask you if it is possible/recommended to make the constraint scoring implementation access an object (singleton) that stores the constraint parameters (eg. weights and constants that could be defined in a configuration table), from the class that implements ConstraintProvider?