How to code an index which is defined as for each and in the same time to sum over its variable range?

Answered

Ibrahim Fikry

October 03, 2020 22:17

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I would appreciate your help in the below constraint, where we are using for loop for defining for each and at the same time inside the constraint. This means that If t=3, I will be I[j,3] and it should be summed from 1 to 3 inside the constraint itself.

 

  

Any help?

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  December 06, 2024 00:41

  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

  October 05, 2020 09:09 Edited

  Hi Ibrahim,

  You did not specify which terms are variables and which are scalar values so I just assumed that \(I,q,\) and \(d\) are all variables.
  I think what you need can be achieved via the function addVars() and quicksum() with two \(\texttt{for}\)-loops

  import gurobipy
  from gurobipy import *
  
  model = Model("test")
  
  Nc = [0,1,2,3,4]
  T = [0,1,2,3]
  
  I = model.addVars(Nc, T, name="I")
  q = model.addVars(Nc, T, name="q")
  d = model.addVars(Nc, T, name="d")
  
  for t in T:
      for j in Nc:
          model.addConstr( - I[j,t] + I[j,0] + quicksum((q[j,l]-d[j,l]) for l in range(0,t+1)) == 0, "myConstr_"+str(t)+"_"+str(j))
                         
  model.write("test.lp")                        
  
  model.dispose()

  Note that I used the write() function to write a human readable LP file and with that check whether the constructed constraints are indeed correct.

  Best regards,
  Jaromił

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  Ibrahim Fikry

  October 05, 2020 09:31

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  Hi Dr.Jaromil

   

  I got it, Thanks for your time and effort. I really appreciate it 

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