NoRel heuristics: is this adding valid inequalities?

Answered

Fabio Schoen

September 23, 2022 13:13

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We are quite puzzled on what happens during the NoRel heuristics. Apparently it is devoted to quickly find good feasible solutions to a MIP problem before solving the LP relaxation.

In our model, however, when using this heuristics, not only a feasible solution is found, but also the LP relaxation value changes. Might it be the case that the heuristics also adds some valid inequalities to the problem? 

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  Jaromił Najman

  • Gurobi Staff

  September 29, 2022 07:45 Edited

  Hi Fabio,

  Might it be the case that the heuristics also adds some valid inequalities to the problem? 

  The No Relaxation heuristic does not add any valid inequalities or cuts. The relaxation bound is computed through feasible solution and model information without having to compute the root relaxation. The idea used to compute the bound is quite simple and does not consider all model constraints. Thus, the lower bound is most often very loose.

  Best regards, 
  Jaromił

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