[SCIP] Disjunction constraints question

[Levinson, Richard J. (ARC-TI)[SGT, INC]]

Hello SCIP team,


I am using disjunction constraints a lot and performance variability which may go beyond the issue of simply reordering the decision variables and constraints. Performance varies significantly with other seemingly minor model reformulations.


Some people have suggested this might be because they hypothesize that the disjunction constraints use Big M which has weak linear relaxations.


But I don't think it uses Big M. My understanding is that the way disjuncts work is that each disjunct is added to the local search problem which seems like a totally different approach than using Big M, and also didn't see anything about Big M in my brief review of the disjunct constraint source code.


My questions are:

  *   Does disjunction constraint handler rely in Big-M reformulation?
  *   Are there any particular search control options which are particularly well (or poorly) suited for disjunction constraints?


Thanks,

    Rich Levinson

    NASA Ames Research Center.
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