Variables fixing in Gurobi's B&B

Answered

Federico D'Onofrio

January 29, 2024 20:20

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Hello,

I am working on a MIQP, let's call its binary variables 'u'. I have a method to compute very good heuristic solutions at each node of Gurobi's B&B and I want to use callbacks to do so. The only thing is that I need to know which components of u are fixed (to 0 or 1) in that node. Is it possible to retrieve this information?

Thanks,

Federico

Related to

• Callbacks
• Heuristics
• Branch-and-Cut
• MIP

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  Simranjit Kaur

  • Gurobi Staff

  January 30, 2024 04:57 Edited

  Hi Federico,

  You can use the Model.cbGetNodeRel() method in a MIPNODE callback to get the node relaxation solution at a node. If your heuristic needs a feasible solution as a starting point, you can use the  Model.cbGetSolution() method in an MIPSOL callback to get a solution.

  Best regards,
  Simran

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