Cut loop at root node of MIP

Answered

Fan YANG

• August 23, 2019 15:23
• Edited

Dear，

I try to learn the operations of Gurobi at root node for MIP.

I have a MIP by C++, and I set

 

model.set(GRB_IntParam_Cuts, 0);

Meanwhile, I write call back function as:

if (where == GRB_CB_MIPNODE) {
 
	if (getDoubleInfo(GRB_CB_MIPNODE_NODCNT) == 0) 
         { cout << "Root node~~" << endl; }
}






When I run the program, Gurobi still prints "Root node" two times in the log.

I would like to know what's the reason of this?

Many thanks,
Fan

1

• 

  Eli Towle

  Gurobi Staff

  • August 23, 2019 16:20

  Hi Fan,

  The MIPNODE callback is called once for each cut pass that occurs at the root node. This is described in more detail in the callback codes documentation.

  I hope this helps. Thanks!

  Eli

  0
• 

  Fan YANG

  • August 23, 2019 16:25
  • Edited

  

  

  

  Hi Eli,

  Thanks for your reply. I set 

  model.set(GRB_IntParam_Cuts, 0);

  which means to shut off cuts.

  Then why Gurobi still inserts cuts?

  Best regards,

  Fan

   

  0
• 

  Sonja Mars

  Gurobi Staff

  • August 27, 2019 06:59

  Hi Fan,

   

  Gurobi is not inserting cuts if you turn off cuts. However, there are also other things going on in the root node, like for examples heuristics and this can also cause a log line to be printed.

  Also can you share a log file?

  Best regards,

  Sonja

  0
• 

  Fan YANG

  • August 27, 2019 13:13
  • Edited

  

  

  

  Hi Sonja,

  Thanks for your reply. I got your point. I attached a picture. 

  0
• 

  Sonja Mars

  Gurobi Staff

  • August 27, 2019 12:55

  OK, cool. This confirms that no cuts are generated and these are more or less heuristics that generate these lines.

   

  Sonja

  0
• 

  Fan YANG

  • August 27, 2019 12:57

  

  

  

  Hi Sonja, thanks for your reply. I understand!

  0

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