How do Precrush and AggFill/Aggregate affect variables

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liu heng

2023年12月05日 06:59

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How do Precrush and  AggFill/Aggregate affect variables?(introduce new vars or remove vars)

関連

• Presolve

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  Michel Soares

  2023年12月05日 14:00

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  As far as I understand, Aggregate and AggFill will mostly remove variables. These are sometimes referred to as "Substitute implied free variables". Disabling Aggregate increases your model solve time on average by more than 40%, but it may be necessary to disable it or make it "less strong" in some cases for numerical errors. (See more on: Achterberg, Tobias & Bixby, Robert & Gu, Zonghao & Rothberg, Edward & Weninger, Dieter. (2019). Presolve Reductions in Mixed Integer Programming. INFORMS Journal on Computing. 32. 10.1287/ijoc.2018.0857. )

  Precrush seems to affect more the constraints numbers, but it may lead to reducing/adding variables as well, as "a side effect" of reducing constraints.

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