Forum Discussion
Bug report: problem.loadproblem not correct
Hi,
In Python, I want to give an MIQP to Xpress directly [i.e. in matrix form], as it saves me the time to construct the model. To do so, I am using the problem.loadproblem functionality explained in the manual (page 260-261). I am also using the examples on FICO's website, e.g. https://examples.xpress.fico.com/example.pl?id=LoadLP_python_4
In that specific example, the qptype = ['I','B'] and mgcols = [0,1], which means that the first variable is an integer variable, while the second variable is a binary variable. However, when I run that example, and I check the solution of that example, it gives the following result:
p.getSolution()
>> [-0.6150098373886015, -0.7725461529183737, -0.9974341677681422]
i.e. neither the first nor the second variable values are integer/binary.
Any ideas why this is and how I can circumvent this?
1 Reply
Hi Richard,
it seems to be a bug of loadproblem(): for some reason it expects either integer/binary variables AND special-ordered sets (SOS) or it doesn't read any. To overcome this temporary bug (to be fixed asap) I suggest using, before solve(),
p.chgcoltype([0,1], ['I', 'B'])
Thanks,
Pietro
