Retrieve a specific subset value of variables

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Sander Mertens

2023年01月31日 15:56

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Hello,

Is there a way to retrieve the value of a subset from a specific variable within Gurobi?

For instance, allot of X variables are created in the form of X[a,b,c,t]. After optimization, I want to retrieve for a variable with a specific a,b,c combination (lets say 'X[1,0,0'), the largest value of t of all the instances where this X[1,0,0,t] = 1. 

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• Python

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• 正式なコメント

  

  Simranjit Kaur

  • Gurobi Staff

  2026年11月13日 01:49

  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

  2023年01月31日 22:30 編集済み

  Hi Sander,
  
  There are several ways you could do this in python (or our interactive interface).  Here is one approach:

  ind = (1,0,0)  # the a,b,c values you want to match
  eps = 1e-6  # tolerance to use for comparison in case values are not exactly 1

  largest_t = sorted([t for (a,b,c,t),v in X.items() if (a,b,c) == ind and abs(v.X - 1) < eps])[-1]

  In this approach we loop through the X dictionary (whose values are variables) with a list comprehension, finding those t values for which the a,b,c indices match and whose variable value is 1 (or close enough to 1).  The list of t values is then sorted from smallest to largest and we take the last one using the -1 index.
  
  Note this approach will result in a list index out of range error if there are no t values which satisfy the condition.

  - Riley

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  Sander Mertens

  2023年02月01日 08:48

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  Thank you, works perfect!

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