Extracting Runtime for Root Node

Answered

Elina Joksch

• May 19, 2022 12:36

Dear Gurobi Team,

I am trying to retrieve and print the runtime for solving the root node. Unfortunately my model does not print any value in the end. Is there any mistake in my code? I already checked older posts, but cannot find my mistake.

Thank you very much!

Best,

Elina

def mycallback(model, where):
    if where == GRB.Callback.MIPNODE:
        depth = model.cbGet(GRB.Callback.MIPNODE_NODCNT)

        if depth == 0:
            if model.cbGet(GRB.Callback.MIPNODE_STATUS) == GRB.Status.OPTIMAL:
                print("Root relaxation runtime is", model.Runtime)


m.optimize(mycallback)

Output: 

And I would like to print out this value:

0

• 

  David Torres Sanchez

  Gurobi Staff

  • May 19, 2022 12:48
  • Edited

  Hi Elina,
  
  The correct syntax to obtain the runtime in a callback is:

  runtime = model.cbGet(GRB.Callback.RUNTIME)

  As shown in the Callback Codes page, this attribute is available everywhere except when \(\texttt{where}=\texttt{GRB.Callback.POLLING}\).
  
  Cheers, 
  David

  0
• 

  Elina Joksch

  • May 19, 2022 15:05

  

  

  Hey David,

  thank you very much! This worked perfectly. Is it now possible to print those numbers also "in the end" to extract those numbers and compare it with different optimizations?

  Best,

  Elina

  0
• 

  David Torres Sanchez

  Gurobi Staff

  • May 20, 2022 14:20
  • Edited

  Hi Elina,
  
  Glad it worked.
  Of course, from the Python Callbacks section:

  If you would like to pass data to your callback function, you can do so through the Model object. For example, if your program includes the statement model._value = 1 before the optimization begins, then your callback function can query the value of model._value. Note that the name of the user data field must begin with an underscore.

  So, in your case, you can set \(\texttt{model._runtime}=0\) at the beginning, update that attribute in the callback, then finally query it at the end of the optimisation.

  Cheers, 
  David

  0

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