Marika Karbstein

For the variables  a = model.addVars(m, vtype=gp.GRB.CONTINUOUS, name='a') no lower bound is defined. The default lower bound is 0. Hence, the solution you mention is not feasible. a = model.addVar...

Did you check the model you created? You could write the LP file with model.write("model.lp"). What are the values for p and v/w? Can you post the lp file here? 

In order to improve the feasible solution finding process you could start by setting the MIPFocus parameter to 1. You could also try one of the following three: ImproveStartNodes, ImproveStartGap, ...

At least one of the entries of  \(\texttt{c_C_profit_margin[c] }\) seems to be not a number but "Nan". Please make sure that you provide real numbers as objective values for variables.

If you set BestObjStop, the solution process is stopped as soon as a feasible solution whose objective value is at least as good as the specified value is found. So with this parameter setting, it ...

Please check this article How do I resolve the error "Model is infeasible or unbounded"? – Gurobi Help Center To get a continuous relaxation of your MIP model you can use model.relax() (or appropri...

The line flow = m.addVars ( commodities , arcs , obj = cost , name =" flow ") defines a variable for each combination of commodities and arcs. Each such variable is added to the objective with coe...

Hi Tomas, You can add an objective via the setObjective method. This is then the primary objective. You can add multiple objectives using the setObjectiveN method. If an objective was already set w...

I think you need to call a model update before printing the attribute.  Model modifications (bound changes, right-hand side changes, objective changes, etc.) are placed in a queue and are applied t...

Hi Marco, Your example is not reproducible, so I cannot see where exactly your problem is. So far there are only continuous variables defined. But you mentioned binary variables in your first post ...