Problem with automating testing of multiple scenarios in IBM ILOG CPLEX Optimization Studio

Question

I am having trouble automating the testing of several scenarios with CPLEX.

I want to test several scenarios where I play around with the weight of the weighted sum of my objective function and the ratio.

Example: W1=0.2, W2 = 0.7, and W3=0.1 with ratio[1]=0, ratio[2]=0, and ratio[3]= to start with. Then, I want my code to increment only ratio[3] from 0.1 to 0.7.

The problem is that when the tool writes my results to my Excel file, I get the following results for my variables IloNumExp and IloNumVar in my Excel file.

Here are my variables:

COUTTOTAL: Total cost to complete the project.
Cmax: Time to complete the project.
QTEREMP: Quantity reused. Compared to the other two, we want to maximize this variable.

Parameter:

W1, W2, and W3 are the weights assigned by the user.
S1, S2, and S3 are correction factors to ensure that each variable has the same degree of importance.
esti***: Maximum and minimum values depending on whether I maximize or minimize just one variable.

FYI : I tried using Gemini to help me execute the automation portion. I can change that part without any problems.

minimize W1 *S1*((TOTALCOST-estiMinCost)/(estiMaxCost-estiMinCost)) +     W2*S2*((Cmax-estiMinTime)/(estiMaxTime-estiMinTime)) - W3*S3*((QTEREMP-estiMinQTEM)/(estiMaxQTEM-estiMinQTEM));

//Constrait....
subject to {
...
}


main {
    var ofile = new IloOplOutputFile("resultats_scenarios_ratio2_varie.csv");
    ofile.writeln("W1;W2;W3;ratio[1];ratio[2];ratio[3];Objectif;COUTTOTAL;Cmax;QTEREMP");

    var r2_start = 0.0;
    var r2_end = 0.2;
    var r2_step = 0.1;

    for (var r2_val = r2_start; r2_val <= r2_end + 0.0001; r2_val += r2_step) { 
        for (var w_index = 1; w_index <= 3; w_index++) { 
            
            var currentW = thisOplModel.W_combinaisons[w_index]; 
            
            W1 = currentW[1];
            W2 = currentW[2];
            W3 = currentW[3];

            for (var r3 = 0.0; r3 <= 0.7 + 0.0001; r3 += 0.1) {
                
             
                var tempRatio = new Array(4); // Taille 4 pour supporter les index 1, 2, 3

                tempRatio[1] = 0.0;     
                tempRatio[2] = r2_val;  
                tempRatio[3] = r3;     
                
                writeln("--- Résolution : R2=", ratio_script[2], ", W=(", W1, ", ", W2, ", ", W3, ") et R3=", ratio_script[3], " ---");

        if (cplex.solve()) {
    
            ofile.writeln(W1, ";", W2, ";", W3, ";", 
                    //CORRECTION : Utiliser ratio_script au lieu de ratio
                                ratio_script[1], ";", ratio_script[2],    ";",ratio_script[3], ";",cplex.getObjValue(), ";", thisOplModel.TestCOU, ";", thisOplModel.Cmax, ";", thisOplModel.QTEREMP);

} 
                else {
                     ofile.writeln(W1, ";", W2, ";", W3, ";", 
                    ratio_script[1], ";", ratio_script[2], ";", ratio_script[3], ";",
                    "No Solution", ";", "N/A", ";", "N/A", ";", "N/A");
                    }
                 }
        }
    }

enter image description here

Any solution ?

Alex Fleischer · Accepted Answer · 2025-11-18 09:13:37Z

1

In your model, I guess you have not solved yet when you do the display or write into a file.

For example,

dvar int x;
dexpr int obj=2*x;

subject to
{
  x==1;
  obj==2*x;
}

main
{
  thisOplModel.generate();
  //cplex.solve();
  writeln(thisOplModel.x);
  writeln(thisOplModel.obj);
}

gives

[a IloNumVar]
[a IloNumExpr]

But as soon as you uncomment

cplex.Solve();

You get

1
2

answered Nov 18 at 9:13

Alex Fleischer

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4 Comments

Félix Veillette Nov 18 at 19:28

Thank you ! I have another problem now, but this one is gone. Thank you again !

Félix Veillette Nov 19 at 2:32

Perhaps you could also help me with another error in this code. When I added your solution “thisOplModel.generate();”, my Excel file finally had some entries. However, I noticed that my parameters W1, W2, W3, ratio[1], ratio[2], and ratio[3] are never modified. Do you have any idea how I can modify the parameter values in my code? I tried adding thisOplModel.W1, but I got the error message: Scripting runtime error: Element “W1” cannot be modified from main scripting. I am using version 22.1.1. I tried creating a scenarios.ops file, but that didn't work either. Thanks in advance.

Alex Fleischer Nov 19 at 8:17

Can you log a new question in stackoverflow ?

Félix Veillette Nov 19 at 16:57

Done. Thank you !

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