Originally posted by: MatthGond

Hello,

I have a problem in which some tasks have to be scheduled and where the tasks have setup times depending of the previous task. (case 1 of this example: https://www.ibm.com/support/knowledgecenter/SSSA5P_12.7.0/ilog.odms.cpo.help/CP_Optimizer/User_manual/topics/designsched_setup.html )

The objective function is to minimize the setup times (and not the makespan).

How can I get the sum of the setup times of the solution given by IloNoOverLap and use it into the objective function ?

Thank you very much for your help.

Matth

Originally posted by: Petr Vilím

Hello,

there is an example how to model setup cost (setup times and setup costs are considered independently as they may differ), see section "Sequence-dependent setup costs" here:

https://www.ibm.com/support/knowledgecenter/SSSA5P_12.8.0/ilog.odms.cpo.help/CP_Optimizer/User_manual/topics/designsched_costs.html

If in your case setup times and setup costs are the same then you may use the same matrix for setup times and for computation of setup cost (although for cost you have to use type IloIntervalArray2 and for transition times type IloTransitionDistance). Or you may use expression startOfNext, but I think that that the approach described in the documentation propagates more. You man also try to experiment with parameter ElementInferenceLevel (indexing an array by decision expression is called an element expression).

Best regards, Petr

Originally posted by: MatthGond

Thank you very much for your help, it is very helpfull.

Best regards,

Matt

Originally posted by: MatthGond

Dear Petr,

I try your suggestion and it works with

IloIntExpr totalCost(env);  
for (IloInt i=0; i<n; ++i)  
  totalCost += M[type[i]][IloTypeOfNext(machine, act[i], last, abs)];    
model.add(IloMinimize(env, totalCost));   

Is it possible to have a totalCost which are floats?

When I try IloNumExpr totalCost(env), with IloArray<IloNumVarArray >M I have the following error message

---------------------------
Error: Invalid parameters for function element. Candidates are:
   intExpr element(intExprArray array, intExpr subscript)
   intExpr element(intExpr subscript, intExprArray array)

-------------------------------


Thank you very much for your help
 

Originally posted by: ChrisBr

Hello,
Indeed element expression on IloNumVarArray is not defined. But element expression on IloNumArray exists.
In this case, you can have a float totalCost.
Are you sure you need an IloNumVarArray?
Regards,
Chris.

Originally posted by: MatthGond

Thank you very much Chris,

you are right, I do not  need an IloNumVarArray and it works with IloNumArray.

Matth