Originally posted by: trebron

Dear all,

OPL offers the possibility to set the objective-coeeficients by OPL-Script

 for( i in model.idx){
//     model.getObjective().setCoef(model.x[i],5);
     myCplex.setObjCoef(model.x[i],20);
  }

Is there as well a getter-method for the coefficient, like, e.g.

    model.getObjective().getCoef(model.x[i]);
     myCplex.getObjCoef(model.x[i]);

Cheers,

   Norbert

Hi,

I do not have any nice way in mind but two workaround:

1)

Use IloLinearNumExprIterator linearIterator() after an external java call

2)

Do a white solve in order to know the coef as in

dvar float+ Gas;
dvar float+ Chloride;


maximize
  40 * Gas + 50 * Chloride;
subject to {
  ctMaxTotal:     
    Gas + Chloride <= 50;
  ctMaxTotal2:    
    3 * Gas + 4 * Chloride <= 180;
  ctMaxChloride:  
    Chloride <= 40;
}

main
{
 thisOplModel.Gas.UB=1;
 thisOplModel.Chloride.UB=0;
 thisOplModel.Gas.LB=1;
 thisOplModel.Chloride.LB=0;
 thisOplModel.generate();
 cplex.solve();
 writeln(cplex.getObjValue());
 
}  
 

which gives 40

regards

Originally posted by: trebron

Dear Alex,

many thanks for your reply.

To me it is surprising that there are setter-Methodsbut no getter-Methods. Changing the coeff can do more harm than just having a look at it ...  Can you put it on the "wish-list"?

Concerning your workarounds:

(1)  Seems to fail as well, as the hasNext() method always returns null in that setting, i.e. you can not iterate over the variables.

(2) Seems to me like 'overkill' in order to obtain the objective coeeficients. That works well for your small example. For more compex problems it is out of scope to wait several hours for the problem to be solved in order to access the objective coefficients.

Best regards

    Norbert

Hi,

do not hesitate to log a wish at

http://www.ibm.com/developerworks/rfe/execute?use_case=changeRequestLanding

regards

Now, the wish is logged at

https://www.ibm.com/developerworks/rfe/execute?use_case=viewRfe&CR_ID=53791

anyone can vote ...

And now we have

getObjCoef

{number} getObjCoef(dvar)

Returns the coefficient of a decision variable in the objective expression

and

getCoef

{number} getCoef(ct, dvar)

returns the coefficient of the variable in the constraint; returns 0 if not mentioned

regards