Different upper bound and lower bound for a list of variables

Answered

Ruoyun Chen

February 23, 2021 01:33

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Hi, 

I'm using m.addVars(Candidate, name="load") where Candidate is a tuple list, looks like:

( 1 , 1 )

( 1 , 2 )

( 1 , 3 )

( 2  , 1  )

( 2  , 2  )

( 2  , 3  )

( 3  , 1  )

...

However, I want to add different lb and ub to the variable based on what's in the tuple.  

Such as:

if first_number_tuple > 2:

     if second_number_tuple <2:

          add.Var(lb=x,ub=y,"load")

However, if I add a single variable each time like this, my variable will loose it structure. 

I want to keep the structure in the way of: m.addVars(Candidate, name="load").

How should I do that?

Thanks a lot!

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  June 23, 2025 02:59 Edited

  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?.
• 

  Ruoyun Chen

  February 23, 2021 01:47

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  I guess a more easier way is to change the upper bound and lower bound for the existing variables. How should I do that?

  0
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  Jaromił Najman

  • Gurobi Staff

  February 23, 2021 08:55 Edited

  Hi Ruoyun,

  You can use variable attributes to set the lower and upper bounds after you added the variables to your model.

  An example would be

  import gurobipy 
  from gurobipy import *
  
  m = Model('test')
  Candidate = [(1,1), (1,2), (1,3), (2,1), (2,2), (2,3)]
  load = m.addVars(Candidate, name="load")
  
  for c in Candidate:
      if c[0] > 1: # if first number of the tuple is > 1
      	load[c].lb = -2 # some lower bound
      if c[1] < 2: # if second number of the tuple is <2
          load[c].ub = 3 # some upper bound   
  
  m.write("myLP.lp") # write LP file to check whether it worked

  Best regards,
  Jaromił

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