Silke Horn

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Latest activity by Silke Horn
  • Silke Horn commented,

    There are a few things I notice from your log: First of all, the error message from the scheduler says TIMEOUT. So I guess more time would help. :-) Why does it time out? Is there a hard limit on ...

  • Silke Horn commented,

    You could model the expression \(\lfloor x\rfloor\) for a decision variable \(x\) by introducing a new integer variable \(y\) and adding the constraints $$y <= x$$ $$y + 1 >= x + \epsilon$$ where \...

  • Silke Horn commented,

    Hi Buddi, Welcome to Gurobi! To define sets, you can use anything that Python offers. E.g. you could define your sets using starting_city = {"City1", "City2", "City3"} and ending_city = starting_ci...

  • Silke Horn commented,

    Hi Yutaka, Do I understand correctly that you want to add a constraint containing a term like the following? $$\sum_{i=0}^m \frac 1{\sqrt{V_i}}$$ What are the \(V_i\)? Are those decision variables?...

  • Silke Horn commented,

    The solver tries to apply all kinds of cuts when solving a model and chooses automatically how aggressively each kind of cut is applied. In the final overview, you only see the ones that were not d...

  • Silke Horn commented,

    Hi Henrik, When using the barrier algorithm, the random seed affects mostly the ordering (and maybe the cleanup). For some models it has a bigger influence on running time than for others. I am not...

  • Silke Horn commented,

    You're right. I hadn't paid attention to the objectives and iteration numbers before. Maybe the differences are due to chance? Have you tried running the same settings multiple times with different...

  • Silke Horn commented,

    Hi Henrik, If you look at the logs, you can see that the barrier was a bit faster with the bigger tolerance: 424.06 seconds for 1e-7 versus 428.05 seconds for 1e-9. However, the crossover took a lo...

  • Silke Horn commented,

    I am glad you could figure it out. From what I have seen, your code looks all right now. The last screenshot shows a Gurobi log, which means that the solver is running and optimizing your model. De...

  • Silke Horn commented,

    You create a (and b) variables with indices from 1 to 24. In the problematic constraint, however, you are trying to access a['Delta', 25] (which does not exist). Where you create the problematic co...