How to use callback to save the objvalue output of each iteration of gurobi to an array or txt file

Answered

Bin Du

March 20, 2023 08:41

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Hello sir, I am a scientific researcher. I have designed a warm_up algorithm for a certain type of problem. I want to get the value and time of each iteration of gurobi. I know that I can output them to the console or log file. But there is too much redundant information, can we just save the objective function value and iteration time of each iteration directly?

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• Callbacks

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 13, 2026 01:46

  This post is more than two 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 try Gurobot, our chatbot interface offering instant, expert-level support.
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  Elisabeth Rodríguez Heck

  • Gurobi Staff

  March 20, 2023 14:13 Edited

  Hi Bin,

  You can query the current best objective, current best bound, and runtime using the OBJBST, OBJBND and RUNTIME Callback Codes.

  Here is an example Python code of how to query these attributes and save them into an array.

  import gurobipy as gp
  from gurobipy import GRB
  
  def data_cb(model, where):
      if where == gp.GRB.Callback.MIP:
          cur_time = model.cbGet(gp.GRB.Callback.RUNTIME)
          cur_obj = model.cbGet(gp.GRB.Callback.MIP_OBJBST)
          cur_bd = model.cbGet(gp.GRB.Callback.MIP_OBJBND)
          model._data.append([cur_time, cur_obj, cur_bd])
  
      if where == gp.GRB.Callback.MIPSOL:
          cur_time = model.cbGet(gp.GRB.Callback.RUNTIME)
          cur_obj = model.cbGet(gp.GRB.Callback.MIPSOL_OBJBST)
          cur_bd = model.cbGet(gp.GRB.Callback.MIPSOL_OBJBND)
          model._data.append([cur_time, cur_obj, cur_bd])
  
      if where == gp.GRB.Callback.MIPNODE:
          cur_time = model.cbGet(gp.GRB.Callback.RUNTIME)
          cur_obj = model.cbGet(gp.GRB.Callback.MIPNODE_OBJBST)
          cur_bd = model.cbGet(gp.GRB.Callback.MIPNODE_OBJBND)
          model._data.append([cur_time, cur_obj, cur_bd])
  
  model = gp.read("/Library/gurobi1000/macos_universal2/examples/data/glass4.mps")
  model._data = []
  model.optimize(data_cb)

  Best regards,

  Elisabeth

  1

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