Mario Ruthmair

Since I do not know the exact definition of your optimization problem and the corresponding model formulation, it is hard to say where there is an issue. If you could give a textual and mathematica...

Hi Jordi, In the flow conservation constraints (last set of constraints above), you do not consider the arcs from and to the depot. You need to include them here. If this results in infeasible solu...

Hi, The Gurobi C++ interface can be used with the precompiled libraries gurobi_c++*2017.lib with Visual Studio 2017 but in some cases (and usually with different IDEs), we recommend compiling the C...

Hi Jordi, I could not resist diving deeper into your case (I am VRP-addicted). After relating your IIS with your model formulation, I found no flaw in your code and model.The only explanation I hav...

Hi Jordi, First, I would recommend to assign names to your variables via x = mdl.addVars( ..., name="x")u = mdl.addVars( ..., name="u") Usually, this helps a lot for debugging. Michel already argue...

Hi Sajjad, I am not sure if I understand your request correctly. If you only relax the general integer variables and keep the binary variables, you indeed obtain a relaxation. However, it cannot be...

Yes, exactly. If the variable names are the same, you can use MIP starts to hand over an initial solution.

Handing over multiple infeasible (or partial) solutions to the solver via MIP starts is possible. The solver then tries to repair (or complete) the solutions, but there is no guarantee that this wo...

With implementing your own branch-and-bound, you would not use Gurobi at all or use Gurobi only to solve node LP relaxations. You would do your own branching, etc. If you want to use Gurobi's bran...

Hi Koen, I quickly scanned through your message and try to answer at least some of your questions: In general, VRPs are notoriously difficult to solve. State-of-the-art algorithms involve some of ...