Improved NoRel heuristic logging
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I find in general the NoRel heuristic a very good method for finding feasible solutions on very large MILP problems. However, the output log about the progress is not very user friendly/hard to interpret. It would be very nice to have a more detailed output about the search progress (e.g remaining time, gap wrt best bound, ...)
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Dear Pablo,We're glad to read that NoRel helps on your models, and would be interested in looking at them, if you can share them.Some details about the NoRel heuristic appear at https://support.gurobi.com/hc/en-us/community/posts/9282521673745-What-is-phase-1-solution-. I know that you were already aware of this post, as you commented in it. But I mention it here for others who may not have come across it.Let me add other information. In phase 2, when it has a feasible solution, NoRel tries to improve it. But that improvement process is incomplete, and NoRel may not find better solutions that exist, even if given more time. This is the reason why the time (or number of work units, to keep a deterministic behaviour) to spend on NoRel has to be specified by the user. Given that the time is specified by the user, it wouldn't really add much information if Gurobi would display the remaining time.The NoRel heuristic runs before the root node is computed, and Gurobi may not know a lower bound to compute a gap. But, indeed, even when it does, the gap is not displayed and this is something we could change.
Note that if a lower bound is known, and NoRel finds a solution that's close enough to satisfy the MIPGap, Gurobi will stop. So the gap is computed and checked, even if that is not displayed.Thanks for your input. We'll try to improve the NoRel log in future versions. Let us know if you have other questions.Xavier1
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