FarkasDual and Barrier method

回答済み

Dong Han

2024年03月18日 23:12

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Hello team,

I am trying to use barrier method to solve a LP model. In some cases, my model will be infeasible and I would like to get the FarkasDual. The thing is I cannot access the FarkasDual since there is always an error code 10005. But I am able to obtain FarkasDual when using simplex method. I am wondering if  there is something wrong with my code or gurobi would not provide FarkasDual when using barrier method(which seems inconsistent with user manual.)

Thank you very much.

関連

• Barrier

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:28

  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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  Riley Clement

  • Gurobi Staff

  2024年03月18日 23:34

  Hi Dong Han,

  In order to provide a Farkas dual there needs to be a basis.  When wanting the Farkas dual users need to set InfUnbdInfo=1 which:

  Determines whether simplex (and crossover) will compute additional information when a model is determined to be infeasible or unbounded

  Perhaps this would be better phrased as

  Determines whether additional information is computed when a simplex basis is available (from simplex or crossover)

  Farkas duals can sometimes be obtained with barrier, but if your model is being declared infeasible mid-barrier then there will be no basis, and a Farkas dual will not be available.

  Currently there is no workaround for this, so either primal or dual simplex will be needed in your case.

  - Riley

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  Dong Han

  2024年03月18日 23:49

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  Hi Riley,

  Thank you very much for your quick reply. It helps a lot !

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