How to define constraint about consecutive periods in optaplanner - optaplanner

Question

In my optaplanner project i have periods with fixed duration.
For some of them there is a medium constraint that they should be scheduled in a row, occupying for example 5 directly adjacent timeslots.
I want to use Java constraints streams but dont manage to define this constraint using the timeslot-pattern.
I know that this constraint can be defined using the time-grain-pattern as suggested by https://stackoverflow.com/a/30702865. I have done this and it works. But I want to compare timeslot-pattern to time-grain-pattern because the have different behaviour when it comes to escape local maxima. The problem with time-grain-pattern is that those 5 periods could also be sheduled in every possible partition of 5 (eg. as 2 + 2 + 1).
Has anyone a hint on how to define the constraint using timeslot-pattern?

Answer 1

You may want to try using the newly added ifExists() building block. Without knowing your actual domain model, I imagine the constraint to look like this:
private Constraint twoConsecutivePeriods(ConstraintFactory constraintFactory) {
return constraintFactory.from(Period.class)
.ifExists(Period.class, equal(Period::getDay, period -> period.getDay() + 1))
.penalize("2 consecutive periods", period -> ...);
}
Consequently, ifNotExists() may be used to achieve the opposite. We have examples of both in Traveling Tournament OptaPlanner example.
Please note that this API is only available since OptaPlanner 7.33.0.Final onward.

Answer 2

I solved the problem using ConstraintCollectors.toList() as follows:
factory.from(Period.class).groupBy(Period::getCourse, ConstraintCollectors.toList())
.penalize(id, score, (course,list)->dayDistributionPenalize(course,list));
and
public int dayDistributionPenalize(Course course, List<Period> list) {
var penalize = 0;
var dayCodes = dayCodesFromPeriodList(list);
for (var dayCode : dayCodes)
if (!getAllowedDayCodes(course).contains(dayCode))
penalize++;
return penalize;
}
Where getAllowedDayCodes() returns for example 0111110000, 0230000000 or 0005000000 etc. from a hash-map if a course has to have 5 consecutive periods.