Advice for Planning Groups of "All or Nothing" Planning Entities

[crispzendisc]

Hello!

We are working on a scheduling problem where activities are allowed to be unassigned (unassigning an activity incurs a medium penalty). We are introducing a new type of constraint where some sets of activities must either all be assigned a timeslot, or none of them should be assigned a timeslot. Planning one or multiple of these activities but not all of them incurs a hard penalty.

We are seeing that if we send in more than ~4 activities that all require each other, the solver never finds the best solution of scheduling all of them (which would be 0hard/0medium/0soft), and instead unassigns all of them (getting instead 0hard/medium/0soft). We think it's because every intermediate move between having everything unassigned and everything assigned breaks hard constraints, and nothing is "guiding" the solver to the best solution.

Does this seem like a good use case for implementing a custom move which assigns (or unassigns) all of these dependent activities at once? Or are there other approaches we could consider? Note that each individual activity could have their own set of possible timeslots that are not shared with any other activities.

Thanks in advance for any thoughts!

[triceo]

Hello @crispzendisc!
You are absolutely correct in your root cause analysis, and in the solution - this is a prime use case to introduce a custom move. The solver can't dig itself out of this hole on its own.