Ordering of binary variables in branch and bound tree

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Richard Li

• June 26, 2023 05:01

How does Gurobi order the binary variables? I.e., how does it decide which binary variable is the root node, which ones are the children, etc.

 

I believe for my problem I have a more optimal ordering than random ordering - I want to force Gurobi to use that information.

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  Mario Ruthmair

  Gurobi Staff

  • June 26, 2023 10:41

  Hi Richard,

  The branching on binary variables in Gurobi's branch-and-bound algorithm follows a set of complicated rules that depend on many criteria, i.e., set of fractional variables, current bounds, branching strategy, etc.

  You can control the branching strategy via parameters VarBranch and BranchDir.

  But what you probably need in your case is to define branching priorities via variable attribute BranchPriority. Variables with a higher branching priority have a higher chance to be selected during branching.

  Best regards,
  Mario

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