How to properly write a constraint with the right hand side needs to choose among three possible numbers

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Sabrin Rashwan

2020年07月04日 16:45 編集済み

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I have a constraint with the right-hand side that needs to choose among three possible numbers. Regardless the left handside, my focus now is on the right-hand side. The constraint is shown in the next image. I set the f parameter as follows

f = 1 if i in P else -1 if i in D else 0

Note: Cr contains P and D

By the way, this is my trial for the left- hand side.

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  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 03:10 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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  Eli Towle

  • Gurobi Staff

  2020年07月06日 19:53 編集済み

  Hi Sabrin,

  Since \( f_i^r \) is indexed by both \( i \) and \( r \), you will need something like a dictionary or a function that maps the different values of \( i \) and \( r \) to their respective \( f \) values. E.g.:

  f = {(r, i) : 1 if i in P else -1 if i in D else 0 for r in R for i in Cr[r]}

  Then, you can use \( \texttt{f[r, i]} \) on the right-hand sides of the constraints.

  I see that \( y_{ij}^r \) is dependent on \( r \) in your mathematical formulation. However, in your code, you use \( \texttt{yr[i, j]} \), which has no dependency on \( \texttt{r} \). Is there a reason why the \( \texttt{y} \) variables in your code have no dependency on \( \texttt{r} \)?

  Thanks,

  Eli

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  Sabrin Rashwan

  2020年08月06日 13:52

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  Thanks a lot I was searching for something like that. 

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  Sabrin Rashwan

  2020年08月06日 13:57

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  With regard to the yr[i,j] I have corrected to yr[r,i,j]

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