Retrieve removed variables after presolve

Answered

Xinshuo Yang

• March 11, 2023 18:46

Is there a way to retrieve the removed variables (especially the binary variables) after presolve for MIP? I assume the values of those variables have been determined by the presovle and should be stored somewhere.

 

Thanks,

Xinshuo

0

• 

  Jaromił Najman

  Gurobi Staff

  • March 13, 2023 15:08

  Is there a way to retrieve the removed variables (especially the binary variables) after presolve for MIP?

  No, it is currently not possible to get particular variables which have been removed in presolve. You could generate the presolved model via the presolve method, compare it to the original model, and try to find which variables might have been deleted or aggregated in the presolve step. Please note that some presolve reduction are non-trivial and there is no necessarily a simple mapping from presolved variables to original variables. You can find more information in the Knowledge Base article How does presolve work?

  Best regards, 
  Jaromił

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