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Why do I encounter numerical issues when solving the model?

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3 comments

  • Marika Karbstein
    Gurobi Staff Gurobi Staff

    What Gurobi version did you use? Do you use any non-default parameter settings (apart from NumericFocus and BarHomogeneous)?
    I tested the model with Version 10 and 11 and default settings and get:

    Model is infeasible or unbounded

    Setting DualReductions=0, the result is infeasible. 
    Gurobi also computes an IIS with 9 constraints. See How do I use 'compute IIS' to find a subset of constraints that are causing model infeasibility?

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  • Jie Zhu
    First Comment
    First Question

    Thank you very much for your reply. Since the model can be solved after slightly relaxing the right-hand side of the constraints, does this indicate that the reason for the "Numerical trouble encountered" message is likely due to the model being infeasible?

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  • Marika Karbstein
    Gurobi Staff Gurobi Staff

    I'm not sure what you mean. As I mentioned, I cannot reproduce the numerical error with the model you shared. If you see a numerical error but can solve your model without any problems if you change some right-hand sides, it could be that the model before was infeasible. At least, it was not possible to find a feasible solution.

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