Ronald van der Velden

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Activity overview

Latest activity by Ronald van der Velden
  • Ronald van der Velden commented,

    Hi Johnpaul, We don't have a full example available. However, once you have the code for constructing and solving the full model, the changes are relatively small. Here are the tricks you need: Af...

  • Ronald van der Velden commented,

    Hi Sergei, Have you looked into indicator constraints already? You could create a single binary variable. Then you create one indicator constraint saying if my binary is 0 then constraint 1 must ho...

  • Ronald van der Velden commented,

    Hi Quin! These are interesting, but also broad questions :-) I'll just share the first that comes to mind, but others may have additional ideas and you may want to add details to guide us in the ri...

  • Ronald van der Velden commented,

    In addition to the above - to answer your last question explicitly: No, that approach won't work since both parts of the objective use the same index 0. If they would use a different index (0, 1) f...

  • Ronald van der Velden commented,

    Hi Lorenz, You mentioned "Since my whole model is very complex for large model". Does this mean the model formulation is as above, but runtime increases as you add workers/shifts/days? Can you give...

  • Ronald van der Velden commented,

    Does the error occur at the last line of your code (model.update) or in a different place? It would typically occur when you try referencing a constraint later, but I notice you don't store the res...

  • Ronald van der Velden commented,

    Hi, What I meant was - have you implemented the approach I suggested and/or tested the model that is discussed in Gurobi Finance? If that leads to errors, could you share a reproducible piece of co...

  • Ronald van der Velden commented,

    What is the problem you're observing? 

  • Ronald van der Velden commented,

    Hi, Because of your question and you mentioning "risk", I suspect you may be interested in the Gurobi Finance project. The linked page includes a nice and clean way to express this risk formula usi...

  • Ronald van der Velden commented,

    Hi, I suspect the part "<= 21" should move after the for-loops: m.addConstr(sum(p[n,s] for n in range (N) for s in range(S)) <= 21, "jadwal")