Crossover Takes Long
AnsweredHello,
I have a large size MIP model and I could come up with a decent feasible solution (have set it as the MIP start value). In the current Gurobi solution process, the root crossover subprocess takes most of the solution time. Are there anything /parameters I should try to reduce the solution time?
Thanks.

Hi,
One way of reducing the time spent in Crossover is to improve the numerical quality of the final Barrier solution point. For this you can try experimenting with the BarConvTol parameter. The tighter this parameter is set, the better (usually) the final numerical quality of the Barrier solution point becomes.
You could try experimenting with the Crossover parameter and/or the CrossoverBasis parameter.
If your model solves in the root node, you could try setting
 Method=2
 Crossover=0
 NodeMethod=2
to turn off Crossover for MIPs by using Barrier in all B&B nodes. Note that if your problem requires many B&B iterations, then this will very likely result in a way slower optimization progress, because the Barrier algorithm will be applied in every B&B node.
Other than the above, improve the numerics of the problem usually improves Barrier and Crossover performance. For more details, see our Guidelines for Numerical Issues.
Best regards,
Jaromił
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