NoRel and integer infeasible models

Answered

Sean Stewart

April 19, 2024 01:22

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If a model is integer infeasible, what happens if you run NoRel on it?  Does Gurobi run forever or does it discover that the problem is infeasible at some point and return an error?

Related to

• Heuristics

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  Riley Clement

  • Gurobi Staff

  April 19, 2024 01:36

  Hi Sean,

  Ignoring NoRel for the moment, when a model is infeasible we may detect it is infeasible during presolve, or we head into branch and cut phase where proving infeasibility can be quite expensive.

  Since NoRel runs after presolve it won't run at all if presolve deduces infeasibility.  If presolve doesn't deduce infeasibility then NoRel will run until it reaches the termination criteria (NoRelHeurTime or NoRelHeurWork).  I don't expect infeasibility could be deduced during NoRel.

  - Riley

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