Hi everyone,

In the example of flexible job shop scheduling of OPL Cplex, some operations of a job can be processed on a subset of different machines.

Suppose now that we have some groups within which jobs are grouped.  We have an additional constraint requiring that the jobs belonging to a specified group must be performed on the same machines.

In other terms, we define 

tuple Groups{
  int jobId;
  int grp;
}

{Groups} Grp=...;

Where Grp contains pairs of jobs and groups within which they are grouped.

I would like to add a constraint specifying this constraint by constraint programming, but I do not see how to achieve this.

Thanks in advance

------------------------------
Ali Balma
------------------------------

In the code you used, two jobs will not be able to be processed on the same machine because the machines that can execute the operations of a job are disjoints. So I assume that you have such a constraint at operation level. 

Considering a group of operations, if we want to force them to be executed on the same machine, you have to gather  

1. the common set of machines that these operations can be processed on, say M
2. the set of corresponding modes intervals for each machine say A(m, id), where m is the machine and id the mode id

then for each machine m in M, state the following constraints :

        presenceOf(A(m,0)) = presenceOf(A(m, id)) for each id  > 0  

This will force the operations of a same groupr to be processed on the same machine.