about the constraints changed with variables

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Hu Zhenghao

2022年07月17日 03:03

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Eexcuse me, in my problem, I have several constraints changed with variables. For example I need to achieve the model has following logic:

if p[0]>=4:

   model.addConstr(p[1]<=1.5)

else:

   model.addQConstr((p[1]-2.5)**2+(p[0]-4)**2<=16)

the logic of the problem is like this where p is my variable. How can I code this nonlinear constraint.

Thanks

 

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2025年11月16日 23:32

  This post is more than three 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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  Jonasz Staszek

  • Community Moderator

  2022年07月18日 06:19

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  You can do it via indicator constraints. Perhaps this post will give you an idea of how to go about this.

  Additionally, I would suggest that you have a look at this entry concerning the creation of quadratic constraints, and make sure that your Python syntax is correct.

  Best regards
  Jonasz 

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  Hu Zhenghao

  2022年07月18日 12:07

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  Thanks for your suggestion, I tried to use a binary variable and use indicator constraints, but the constraint is quadratic. So I added a new variable to define the quadratic equation, it works. I really appreciate your help!  

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  Hu Zhenghao

  2022年07月18日 12:45

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  Actually, my objective is also changed with variables, like :

  if p[9,0]>=4:

     objective=max p[9,1]

  else:

     objective=max p[9,0]

  the expression is simplified.The objective function is segmented and nonlinear. Here the indicator constraints don't work, I also wonder how could I settle this.

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  Jonasz Staszek

  • Community Moderator

  2022年07月18日 13:45

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  I am afraid you can't change the objective this way. But perhaps you can find a way to reformulate your objective in such a way that the change is not required?

  Best regards,
  Jonasz

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