Domain of variable

[samuel-casasdray]

I'm using HiGHs with python and I have some issues about the domain of the variable. Can we specify that we only want a solution with natural number or even binary number ?

[jajhall]

Yes, the type of a variable can be set to highspy.HighsVarType.kInteger and then its bounds used to define the range of integer values that it may take. How you do this in practice depends on how you are defining your model.

• If you are populating an instance of the HighsLp class, then set the entries of the integrality_ vector to the value highspy.HighsVarType.kInteger, and the values of the colLower_ and colUpper_ vectors to the desired bounds.

• If you have built the model by defining variables and constraints, you call the following highspy method, where n is the number of variables that you want to be integer-valued, indices is the list of length n of the indices of variables to be integer-valued, and integrality is a list of length n, all of whose entries have the value highspy.HighsVarType.kInteger. The definition might be cumbersome if you want all your variables to be integer valued, but it allows for simplicity in terms of number of highspy methods and generality of use

  changeColsIntegrality(n, indices, integrality)

Bounds on variables can be changed using the following highspy method, lower and upper are lists of bound values of length n

changeColsBounds(n, indices, lower, upper)

Feel free to ask further questions

[samuel-casasdray]

That's perfect, thanks a lot!
And so I have another question, non-related. Do you know if it's possible to print my model in LP format, in the terminal or in a file, I don't care, I just want to see if I create it well?

[jajhall]

Yes, call h.writeModel("foo.lp"). If you call h.writeModel("") you'll get the model to the screen in a human-readable format

[samuel-casasdray]

That's perfect again, thanks!