What happens after root relaxation has been solved? Long time before exploring further nodes according to log

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  • Matthias Miltenberger

    Hi Hendrik,

    Yes, Gurobi is processing the root node while printing those "0   0" lines. Here's an excerpt from our MIP Logging documentation:

    Note that the explored node count often stays at 0 for an extended period. This means that the Gurobi MIP solver is processing the root node. The Gurobi solver can often expend a significant amount of effort on the root node, generating cutting planes and trying various heuristics in order to reduce the size of the subsequent branch-and-cut tree.

    I hope that answers your question. To reduce the time spent in the root node and start with the branch-and-bound process earlier, you can try reducing the number of cuts being added to the problem via parameters Cuts and CutPasses.

    Cheers,
    Matthias

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  • Hendrik Weber

    Ah yes, thank you so much for the quick response. I probably should have read the documentation first :)
    Thanks!
    Hendrik

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