Modeling the Objective Function in the CPLEX Java API

Question

I#m trying to model the objective function sum(i in Sites,j in Sites, k in Routings)(c[i][j] * x[i][j][k]*TruckKmCost) in Cplex using java.

IloLinearNumExpr expr = cplex.linearNumExpr();
            for (int i = 1; i <= nbFarmer; i++) {
                for (int j = 1; j <= nbFarmer; j++) {
                    for (int k = 1; k <= nbRouting; k++) {
                  expr.addTerm(truckKmCost, c[i][j],x[i][j][k]);   
               }
            }
}

This was my attempt, but the method addTerm only accepts (double, IloNumVar), and I can't convert c[i][j] to IloNumVar, because I need it as an int so i can add my int values to it.

There must be a pretty easy solution, maybe somebody can help me, I'm a little stumped right now.

Thanks a lot!

Daniel Junglas · Accepted Answer · 2020-01-13 10:05:19Z

1

You did not specify whether c[i][j] is a variable or a number. Depending on this there are two different solutions to your issue:

In case c[i][j] is a number then just write expr.addTerm(truckKmCost * c[i][j], x[i][j][k]), that is, merge the two numbers into one single argument to addTerm.
In case c[i][j] is a variable then your objective is not linear but quadratic. In that case you cannot use IloLinearNumExpr but have to use IloQuadNumExpr. The addTerm() of this class takes two variables as arguments.

answered Jan 13, 2020 at 10:05

Daniel Junglas

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