Is the root node included in the nodeCount attribute?

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Jørgen Skålnes

2021年04月22日 14:56

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Hello,
From the documentation of nodeCount it says: "Number of branch-and-cut nodes explored in the most recent optimization." Moreover, under MIP Logging it says that nodeCount is zero whenever the MIP solver is processing the root node. However, it is not clear to me whether or not the root node is included as one of the branch-and-cut nodes. When I am solving a set of MILP instances to optimality some of them reported that nodeCount is 0 and others reported 1. What is the difference between these? Are both solved to optimality in the root node, but one at an earlier point than the other? Or has the MIP solver branched on a variable, but found the optimal solution after just processing one child node?

Best regards,

Jørgen

 

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  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 02:56 編集済み

  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 why not try our AI Gurobot?.
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  Jaromił Najman

  • Gurobi Staff

  2021年06月29日 10:34

  Hi Jørgen,

  Please excuse not getting to you for so long. Currently, it is possible that the NodeCount attribute reports 0 although a B&B line has been printed, i.e., the root node has been solved. This will no longer be the case in a future release and the root node will be properly included in the node count. The NodeCount attribute will only show 0 when the problem has been solved in presolve, i.e., no nodes have been opened. Thank you for reporting this.

  Best regards,
  Jaromił

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