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Why is Gurobi taking so much time to find the optimal solution to objective 2?

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  • Mario Ruthmair
    Gurobi Staff Gurobi Staff


    Only because some objective function "looks" easier than another one does not mean that it is easier to solve.

    For the first objective, the dual bound obtained by the root relaxation is already very near to the optimal value, and an optimal solution has been quickly found by a heuristic (line starting with "H"). So there is no need to start the branching phase.

    For the second objective, it is not clear whether the dual bound is weak (far away from the optimal value), or the built-in heuristics cannot easily find better solutions. Therefore, the resulting gap is still large and potentially needs a large branch-and-bound tree to close the gap. Is there some additional output where you currently only have "......"?

    Best regards,


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