I wanted to expand the job shop problem for the CP-Sat Solver by adding optional tasks,that don’t have to be executed. But my problem is that I don’t really know how “remove” a task from the model if a BoolVar is true.

I added a boolean optional to the class Task and a BoolVar active to the class TaskType

public class Task {
    int machine;
    int[] duration;
    String name;
    boolean optional;
    Task(int machine, int[] duration, String name, boolean optional) {
        this.machine = machine;
        this.duration = duration;
        this.name = name;
        this.optional = optional;
    }
}

public class TaskType {
    IntVar start;
    IntVar end;
    IntervalVar interval;
    BoolVar active;
}

My first idea was that if taskType.active == false, then I don’t add the taskType to the allTasks list, so it isn’t considered by the model as a task that needs to be executed. But to my understanding, there is no way to compare a BoolVar because it’s state is technically undefined (if you know what I mean?)

In the part where we create the taskTypes in the link above, (a part of) my code looks as follows:

if(task.optional) {
    taskType.active = model.newBoolVar(task.name + "_activeStatus");
}

taskType.interval = model.newIntervalVar(
      taskType.start,
      model.newIntVar(task.duration[0], task.duration[1], task.name + "_duration"),
      taskType.end,
      "interval" + suffix);

task.duration is an int array, which has the minimum duration in duration[0] and the maximum duration in duration[1].

At this point I honestly don’t know how to proceed. I thought about setting the duration of taskType.duration to zero if taskType.active == true, maybe by using onlyEnforceIf() , so that it doesn’t effect the final duration of all tasks, and then filter the tasks out in the output. But then again, I haven’t found a way to use onlyEnforceIf() this way.

My problem essentially is that I want to make the taskType “irrelevant” if its BoolVar active is true, maybe by changing an existing IntVars bounds (but I also haven’t found out if that is even possible).

Maybe some of you have a hint for me, thanks in advance.