Different upper bound and lower bound for a list of variables

Answered

Ruoyun Chen

• February 23, 2021 01:33

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

• 

  Ruoyun Chen

  • February 23, 2021 01:47

  

  

  

  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
• 

  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

  2

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