Get the iterations and ObjVal, while "model.optimize(mycallback)" is running

Answered

Gerrit Burmester

November 28, 2019 17:47

• 
• 

Hello together, I build a model to solve an Mixed integer LP. Now I want to output every iteration (or every 100th or so) in the optimizing process (or store the values somewhere.) I tried it with a callback function, but the "where"-value is only 0,1,3 or 6. Therefore it does not go into SIMPLEX, but into MIP. It goes 3 times into MIP and outputs the following: MIP_ITRCNT 0.0 MIP_OBJBND 20539.41417610684 MIP_ITRCNT 0.0 MIP_OBJBND 20539.41417610684 MIP_ITRCNT 7607.0 MIP_OBJBND 1276010.241269448 The last number (7607) is equal to the number of iterations in total, or in other words: when calling model.IterCount after the optimization-process, it has the same number. (also 1276010... is the right objective value) the total number of iterations is right, but how can i get the informations about iteration 1-7606? Even when outputflag is True, there are more information about the iterations, than I can get in the callback. (there every 5 sec the iterations with actual objVal are listet, I want to have every x iterations and not every 5 sec) Thanks for your help and best wishes Gerrit

Related to

• Callbacks
• Multiple Objectives

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  December 06, 2024 00:51

  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?.
• 

  Matthias Miltenberger

  • Gurobi Staff

  November 29, 2019 11:18

  Hi Gerrit,

  If you want to query simplex information you need to use the SIMPLEX callback, i.e. use where=2. Please have a look at the callback documentation and also at the callback examples in your Gurobi installation.

  Cheers,
  Matthias

  0
• 

  Tanmoy Das

  February 28, 2023 16:40

  • 
  • 
  • 

  I also want to get the objective values (two objectives in my moo problem) in each iteration.
   Callback function gives me some ideas. I know my model went through 19 simplex iterations. I need the values of obj1 & obj2 for each iteration. How can I get it in Python API (MIP problem)?
  
  

   

   

  0
• 

  Matthias Miltenberger

  • Gurobi Staff

  March 02, 2023 17:10

  Hi Tanmoy,

  In that case, you would need to use ObjNumber to specify the objective you want to query.

  Best regards,
  Matthias

  0

Post is closed for comments.