Proper way to access LP relaxation?

Answered

Tobias Völk

July 06, 2022 14:59

• 
• 
• 

When Gurobi has solved a relaxation during it's Branch & Bound - Algorithm, I would like to look at the solution of the relaxation in order to add a type of cut which we found in a paper. What is the proper way to ask for the relaxation solution in the callback? Right now I have this, but apparently it does not always work, sometimes it throws an error which I have to catch:

def my_callback(model, where):
    if where == GRB.Callback.MIPNODE:
        try:
            r = model.cbGetNodeRel(model.getVars())
            # ... add cut
        except gp.GurobiError:
            pass

0

• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  November 16, 2025 23:33

  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 try Gurobot, our chatbot interface offering instant, expert-level support.
• 

  Mario Ruthmair

  • Gurobi Staff

  July 08, 2022 12:04

  Hi Tobias,

  You have to additionally check the current state as it is mentioned in the description of cbGetNodeRel().

  Best regards,
  Mario

  0

Post is closed for comments.