Save optimizer state and resume.

Answered

Milin Kodnongbua

July 16, 2023 16:47

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Is it possible for the state of the optimizer to be saved? I want to run Gurobi on an preemptible node and want to resume from the saved state.

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 13, 2026 01:40

  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.
• 

  Simranjit Kaur

  • Gurobi Staff

  July 17, 2023 03:32 Edited

  Hi Milin,

  Calling the optimize() method again on a model will continue the optimisation process from the last state where the optimizer had stopped. Please see a sample code below.

  import gurobipy as gp
  
  #construct your model
  ...
  
  # your custom terminating criteria
  model.params.MipGap=0.05
  ...
  
  # optimize
  model.optimize()
  
  # do something with the solution/s
  ...
  
  #redefine termination criteria
  model.params.MipGap=0.02
  ...
  
  #resume optimisation
  model.optimize()

  Best regards,
  Simran

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  Milin Kodnongbua

  July 17, 2023 04:00

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  Thanks for the response.

  However, I mean load the state to a new instance of solver in a new process. The same solver is not in memory anymore. Is there a way to save/load from disk?

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  Simranjit Kaur

  • Gurobi Staff

  July 17, 2023 04:36

  Hi Milin, 

  It is not possible to save a snapshot of the optimizer state to a disk. One cannot store the branch-and-bound tree or the presolve transformations. However, you can store the solution at the end of a solve by writing the SOL file and use it to warm-start the next solve.  

  Best regards,
  Simran

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