Getting Number of Non-zero Entries in the Constraints After Presolve in Julia

Answered

Henry Mao

• August 05, 2024 04:45
• Edited

Hello Team,

I am a researcher working in economics and I have a question about obtaining specific model information under the Julia JuMP framework. Say that I have set up a generic linear program in Julia and the model has been optimized. I know that I can obtain the number of non-zero entries in the constraint before presolve using 

MOI.get(model, Gurobi.ModelAttribute("NumNZs"))

 

I want to know if there is a way to obtain the number of non-zero entries in the constraint after presolve. I know the information can be retrieved from the log file, but I was wondering if there is a way to obtain the information programmatically without parsing the log file. This would really help with my research. Thanks!

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• 

  Jaromił Najman

  Gurobi Staff

  • August 05, 2024 12:28

  Hi Henry,

  I want to know if there is a way to obtain the number of non-zero entries in the constraint after presolve. I know the information can be retrieved from the log file, but I was wondering if there is a way to obtain the information programmatically without parsing the log file. This would really help with my research. Thanks!

  There is currently no way to obtain the number of non-zeros after presolve has been performed. Currently, the only way to obtain this information is to parse the log output. This can be done via a MESSAGE callback.

  Please note that the NumNZ attribute reports the number of all non-zeros in linear constraints and not the number of non-zeros in a specific constraint.

  Best regards, 
  Jaromił

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• 

  Henry Mao

  • August 05, 2024 20:17

  

  

  Thanks for the answer!

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