Are there any specific settings one should use when no solutions to a MIP are expected?

Answered

Jonah Klein

August 10, 2025 04:25

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I am currently working out a variety of MIP problems using Gurobi. I am trying to use Gurobi to show that these models have no solutions. Are there any settings that I can and should be using to help in this process? 

Related to

• MIP
• Solutions
• Infeasible

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  Riley Clement

  • Gurobi Staff

  August 11, 2025 00:24

  Hi Jonah,

  If you're confident no solutions exist and your simply using Gurobi to confirm this then I'd start with turning heuristics off - they will be a waste of time.  My hunch is that MIPFocus=3 and Presolve=2 would also help, but this is just a guess.

  - Riley

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  Jonah Klein

  August 13, 2025 17:14

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  Hi Riley,

  Thank you for your answer! Turning heuristics off did indeed help, and saved about a third of the computation time in the benchmarks I did. Presolve=2 changed nothing to the number of variables and constraints after presolve, so I am assuming the regular presolve was doing fine. I imagine this might help with other problems where the presolve is more complex. MIPFocus=3 actually slowed down the computations. I should mention that I am optimizing without a function to optimize, i.e. I am optimizing for the 0 function, so there is no gap to take into account. 

  -Jonah

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