Mario Ruthmair

Hi Marcus, Your 2 parameter settings sound reasonable for quickly finding a feasible solution. SolutionLimit=1 actually changes some behavior in the solution process (apart from stopping after 1 so...

Hi Nicolas, Flow problems formulated as (integer) linear programs are not solved via classical max-flow algorithms (like Ford-Fulkerson, Preflow-Push, etc.) by Gurobi. The solver uses LP and MIP te...

Hi Mads, The Big-M model is known to provide only weak dual bounds. There are a few things that can be improved in this formulation, e.g., to avoid the vehicle index k if the fleet is homogeneous. ...

Hi Samuel, It seems that the LP file that Pyomo wrote out does not have the right format, it seems to have "nan" included.You might check whether you have some issues with your input data. Best reg...

It seems you could use the gurobipy Matrix API to handle your vars and constraints. Here is some material: Tutorial video Small example Basically, you can add a matrix variable like this: x = mod...

Hi, As you defined the names of your variables, I would suggest to use two variable dicts, e.g., x = model.addVars(n, vtype=GRB.CONTINUOUS, name="x")y = model.addVars(n, vtype=GRB.CONTINUOUS, name=...

Hi Thuy Anh Pham, Vehicle routing problems are in general very difficult combinatorial optimization problems. State-of-the-art solution approaches involve a highly-tuned and sophisticated branch-pr...

Hi Jake, (1) There are only solution quality attributes related to the model, not to particular variables or constraints. They give you the maximal violations over the whole solution: BoundVio, Co...

Hi Hussein, A quadratic constraint consists of quadratic expressions, i.e., a quadratic expression is only a term involving products of variables, not a complete constraint. In your first case, whe...

Hi,  Modeling and solving VRPs (with TW) is far from being trivial. State-of-the-art models require to implement a branch-and-price or a branch-and-cut algorithm. Compact models (with a polynomial ...