gurobi.QConstr Not Yet Added

Answered

Parijat Mitra

• April 29, 2021 10:34

Hello members,

While modeling my workforce scheduling problem, I have encountered "gurobi.QConstr Not Yet Added" with one of my constraints used in the model. I have many constraints in my model where other constraints are saying 

gurobi.Constr *Awaiting Model Update

Could anyone explain why is this happening so? If it is a case-specific, then I would reply to you back with my specific problem I trying to solve

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• 

  Jaromił Najman

  Gurobi Staff

  • April 29, 2021 11:35

  Hi Parijat,

  You encounter this error due to Gurobi's lazy update approach. You can find more information in the documentation of the UpdateMode. To avoid this error, you have to execute the Model.update() function before using any added constraints and/or variables.

  Best regards,
  Jaromił

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  Parijat Mitra

  • April 29, 2021 13:18

  

  

  

  Thanks for your response, Can you please show a small piece of an example of how to use the Model.update()

  function. 

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• 

  Jaromił Najman

  Gurobi Staff

  • April 29, 2021 14:24

  An example would be

  import gurobipy as gp
  from gurobipy import GRB
  
  # Create a new model
  m = gp.Model("test")
  # Create variables
  x = m.addVar(name="x")
  y = m.addVar(name="y")
  
  m.addConstr(x*y <= 2)
  m.update()

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  Parijat Mitra

  • April 29, 2021 14:27

  

  

  

  thank you Juromil Najman

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