Find redundant constraint in MILP

回答済み

Mohammadreza Chamanbaz

2021年08月03日 04:52

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Hi

I understand that there are some sophisticated methods used in presolve to reduce the size of a model. To the best of my knowledge, the algorithm in presolve comes up with a reduced model and a mapping to recover the solution to the original problem.

My question is whether or not there is a method in Gurobi that can just identify redundant constraints (only constraints). It would be useful (for my case) even if I can identify redundant constraints "after" solving the problem.

Cheers,

Mohammadreza

 

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  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 02:50 編集済み

  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 why not try our AI Gurobot?.
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  Jaromił Najman

  • Gurobi Staff

  2021年08月03日 15:19

  Hi Mohammadreza,

  If by getting redundant constraints you mean to get a set of constraints removed by Gurobi during the presolving step, then this is not possible.

  If however, you mean that you are interested in getting constraints which are redundant in the optimality sense, i.e., are not active at the optimal solution point, then you can use the Slack attribute to check whether a linear constraint is active at the solution point. Note that it is always recommended to work with a small tolerance, i.e., if the Slack of a constraint is < 1e-6 then the constraint is very likely actually active and the small offset is due to numerical accuracy.

  Best regards,
  Jaromił

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