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

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Henry Mao

2024年08月05日 04:45 編集済み

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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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• Attribute
• Julia

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  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:21

  This post is more than two 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 try Gurobot, our chatbot interface offering instant, expert-level support.
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  Jaromił Najman

  • Gurobi Staff

  2024年08月05日 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

  2024年08月05日 20:17

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  Thanks for the answer!

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