Originally posted by: GuilhermeSantos6

Hi there,

I am new to this forum, so I apologize if I make any mistake. I have searched for similar problems but have not managed to find a solution.

I have a model in which a decision variable is indexed by a tuple set, which I define in a .mod file:

//Define tuple
tuple fvts {
 string F;
 string V;
 int T;
 string S; 
 }

//Declare tuple set
{fvts} fvts_ = ...;

//Declare decision variable
dvar int+ sh[<f,v,t,s> in fvts_];

In a separate .mod file, I have a flow control script in which I iteratively changes the upper bounds of N of these variables to 1. To select which variables are updated, a sub-problem (defined in yet another .mod file) is solved, and the decision variables are ranked according to a user-defined function which compares the results of the main model and the sub-model. To do so, I'm using the following script:

main {
    ...

    //main_model is the main model, m3 is the sub-model

    // Generate array of tuples from tuple set
    var list = new Array();
    var j = 1;
    for (var i in main_model.fvts_) {
      list[j] = i;
      j++;
    }
    
    // Order array of tuples according to the value a user-defined function
    list.sort(compareFactor);
    
    //Update the upper-bound of the top N variables
    for (var l = 1; l <= N; l++) {
      var s = main_model.fvts_.find(list[l]);
      main_model.sh[s].UB = 1; 
    }
    
  ...

}

The list is successfully ordered as expected. However, the problem is that at the second iteration of the second loop, I get the error "OPL cannot extract expression: sh#231.". I have isolated this error to the "main_model.sh[s].UB" part, since the "main_model.fvts_.find(list[l])" behaves as expected. However, I know that the decision-variable with that tuple as index exists, and I am not able to access it.

Any ideas on what may causing this error and how to fix it?

Thanks in advance for any help!

Cheers,

Guilherme

Hi,

what happens if you remove

main_model.sh[s].UB = 1;

?

And if you turn that to

writeln(main_model.sh[s].UB);

?

Last, can you post a minimal example so that other users could try ?

regards