MIP bound is greater than reported incumbent solution and reported solution is suboptimal

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Adrian Lipow

2022年07月22日 10:57

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Hi,

when solving a MIP using ConcurrentMIP (as well as some other non-default parameter settings, see linked log-file), Gurobi reports multiple weird things:

1. The reported bound is greater than the incumbent.
2. The log shows that for several iterations before termination, the best bound was already greater than the incumbent (yet this is a different bound than that reported at the end).
3. The reported best objective does not match the one given in the log in the line "No other solutions better than ..."
4. The solution in the log line "No other solutions better than ..." is clearly suboptimal.

The MPS file and log are here: https://rwth-aachen.sciebo.de/s/kGG6AqUeYAz2ZVv

I am running Gurobi 9.5.0 (upgrading to 9.5.2 is not easy because I am not in control of software updates on the machine), so I'm not 100% sure if this may be a bug fixed in one of the two releases since then.

Cheers,

Adrian

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2025年11月16日 23:32

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.
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  Gwyneth Butera

  • Gurobi Staff

  2022年07月22日 11:23

  Related to Number of Threads affects MIP Solution

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  Eli Towle

  • Gurobi Staff

  2022年07月26日 22:24

  Thanks for reporting the issue! This appears to be the same bug that you reported in the post Gwyneth linked. Upgrading to Gurobi 9.5.2 should resolve the issue, though I understand that's not necessarily easy for you.

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