CP-SAT Implement breaks with cumulative constraint

[ajouzali]

We have a complex job-shop problem in which we have a lot of machine breaks with different sizes. With the large number of tasks, the spliting of the tasks using optional interval cause a very big number of variables in our CP-SAT model. So, we are trying to find an alternative implementation. So, the idea is as follows:

• to create a second time dimension X which only increases in the usefull production time and 0 when there is a break

• So, the constraint should be at the end as follows
  1- start(Task) and end(Task) in usefull production interval
  2- X(end(Task)) - X(start(Task)) == Duration(Task)

The problem is our intervals and durations are in seconds and the mapping form and to X would also cause a lot of variables.
Is there any recommendation on how to deal with this case? reference, or an Example?

[lperron]

Hi, have you looked at https://github.com/google/or-tools/blob/stable/ortools/sat/doc/scheduling.md#intervals-spanning-over-breaks-in-the-calendar ?

[ajouzali]

We tried a similar implementation with multi-spanning intervals but we are not happy with the performance. So, we are thinking about a similar concept to what is implemented in routing package (cumulative dimension with map evaluator ). But the seconds grid we use does not help also.

[gregy4]

Can you give us some example ? It is not very helpful to talk generally about large number of tasks or that you are not happy with the performance.

[Hakunari]

Hello! Did you get any solution? I got the same problem.