使用Optaplanner对列表中的项目进行排序

Question

we are currently evaluating optaplanner to be used in our cutting machine schedule optimization project.

How efficiant is optaplanner in sorting a list of items based on rules?

A little bit of background story:

What the customer expects from us is that the tool should optimize the schedule of the cutting machines in such away that it minimizes the down time of them using the following factors:

1. Orders with high priority should go over the machine first. (Hard Score)
2. then orders near its due date. (Medium Score)
3. Minimize the product change occurrence in the schedule, as with every change the machine needs to be down for X minutes for cleaning work. (Soft Score)
4. Minimize the knife position change between the patterns. Every knife position change will take 5 minutes for the operator to set it. (Soft Score)
5. if everything of above is the same, then apply the FIFO method, so the oldest item should go over the machine first. (Soft Score)

We implemented the model using the chainedVariable and shadowVariable, HardMediumSoftScore and the rules above in Drools. Optaplanner does its job very well on the first 4 rules but struggles with the last one. However when I comment out all other rules then optaplanner does it just fine and I see the items being sorted correctly.

Here is the drool rule for the last rule:

rule "sort by ItemNumber"
salience 10
when
    $previousScore : Number() from accumulate(
        TaskGroup(previous!=null, previous.name > name, productType == previous.productType),
        sum(-1)
    )
    $nextScore : Number() from accumulate(
        TaskGroup(nextTaskGroup!=null, nextTaskGroup.name < name, productType == nextTaskGroup.productType),
        sum(-1)
    )
then
    scoreHolder.addSoftConstraintMatch(kcontext,$previousScore.intValue()+$nextScore.intValue());
end

Maybe the rule is not expressed in the right way, but we are having a hard time understanding why the rule does not do its job correctly when used in combination with the other rules.

Let me know if I need to provide more information (my first time posting here).

Thanks in advance for the support.

Answer 1

Some idea's to consider: make rule 3 and 4 a medium Score (switch to HardMediumSoftScore), because rule 5 starts with "if everything of above is the same", so it really deserves it's own score level, the lowest one.

Take a look at the docs section about "fairness constraints". Simply penalizing for each task the square of the difference between it's orderNumber and the previous task's orderNumber might already do what you want. The description of rule 5 leaves some room for interpretation (for example is twice 1 order number too late worse than once 5 order numbers too late?).