In the model I'm trying to build, I have a variable defined as:
Variables
x(i,j) number of motors produced in month i to be delivered in month j ;
In that variable, j must always be equal or greater than i for it to make sense (you can't produce something in this month to be delivered in the previous month). However, I have no clue as to how I can properly model this. I've searched and couldn't find an easy solution to this.
Any ideas?
You should use "variables with limited domains" for this, look here for more details, it is a rather new GAMS feature: https://www.gams.com/latest/docs/UG_ModelSolve.html#UG_ModelSolve_LimitedDomain
So, in your example, it would look like this:
Set limX(i,j) limiting domain of x;
limX(i,j) = ord(j) >= ord(i);
Model m /all, x(limX)/;
...
Edit: Corrected syntax of model statement.
So, I add this, right after declaring the variable:
x.fx(i,j)$(ord(i)>ord(j))=0;
It is fixing the values of the variables you are not using to zero. In your model:
And the results are:
I believe that should do it :)