About using 'LazyConstraints' Parameter

Answered

Junseo Park

August 19, 2025 08:14

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I am currently using user cut with custom Cut.

Which means, I am using model.cbGet, not model.cbLazy in the callback.

However, I am getting objective solutions much more faster when I set the LazyConstraint parameter to 1.

I want to know the reason why this is happening.

Related to

• Branch-and-Cut
• User Cuts

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  Ryuta Tamura

  • Gurobi Staff

  August 23, 2025 11:44

  Hi Junseo,

  Which means, I am using model.cbGet, not model.cbLazy in the callback.

  I think you are talking about model.cbCut, not model.cbGet.  Are you enabling PreCrush=1 when using model.cbCut? PreCrush parameter shuts off a few reductions to apply user cuts. If this is not set, some user cuts may be ignored. LazyConstraint=1 also disables some dual reductions. If PreCrush was not enabled in your code, the user cuts may have been recognized by setting LazyConstraint=1.

  Thanks,
  Ryuta

   

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