root node with integer variables, then relax some for branching phase

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Leandro Coelho

2019年06月07日 08:13

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I have some very large MIPs to solve. I can relax integrality conditions on some variables but realized that doing so makes the root node solve time explode. I guess Gurobi applied cuts and strengthens bounds/coefficients based on the integrality conditions, making the LP relaxation easier to solve at first (with integrality conditions).

Can I solve the root node with integer variables, and after that change the type of some variables, continuing the branching phase with fewer integers, but still benefiting from new cuts/bounds?

Many thanks

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  Simranjit Kaur

  • Gurobi Staff

  2025年06月23日 03:26 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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  Daniel Espinoza

  2019年06月12日 17:08

  Hi Leonardo,

  No, you can not change variable types once optimizatoin has started, you could try using branch priorities so the solver focus more on those you think are more important.

  I Hope it helps,

  Daniel

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