Changing coefficients in the constraint

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Nazmi Sener

2021年08月15日 13:44

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Dear all,

I try to change coefficients of decision variable z for each scenario s. However z is used with two different coefficients. The constraint is given below. How can I do it?

Thanks in advance,

Have a nice day,

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  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 02:50 編集済み

  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 why not try our AI Gurobot?.
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  Jaromił Najman

  • Gurobi Staff

  2021年08月16日 07:50 編集済み

  Hi Nazmi,

  Gurobi reformulates the model such that every variable has exactly 1 coefficient. This means that the sum of your \(z\) variables actually looks like this

  \[\sum_{j \in \mathcal{N}, j \neq k} \left (d_{ij}(s)z_{jk}(s)\right) + (d_{ik}(s) - O_i(s))z_{kk}(s)\]

  Thus, you have to change the coefficient given by \((d_{ik}(s) - O_i(s))\).

  Best regards,
  Jaromił

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  Nazmi Sener

  2021年08月16日 09:31

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  Hi Jaromil,

  Thank you for your quick response. i is not equal to k also. I will try to rewrite this constraint. Another question: How can I change coefficient of any parameter in python? I cannot fully understand.

  Thank you,

  Kind regards,

   

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  Jaromił Najman

  • Gurobi Staff

  2021年08月16日 11:27

  Hi Nazmi,

  You can use the chgCoeff function. To use it, you have to provide the constraint, variable, and the new coefficient value.

  Best regards,
  Jaromił

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