Thanks for the information. Do you think that recomputation in this case could pay off? Furthmore, to turn it into a constraint problem, how could i configure my search in a way that the reified constraint xb==x becomes true/false, without labeling xb. I can not set xb to true/false, because i want the propagation of the other constraints to be the cause that xb comes true/false.
My first idea was double reification. Consider the reified constraint set B=C are the set to minimize so that they still propagate x. I do know the values of B. I could post the constraints D=C with fresh boolean variables D. Adding then boolean reified constraints (val(B)==D)==F. So that F_i indicates that the constraint c_i has the predifined value(or not). I could then minimize on the number of true F's(branching on F). But i do not know how to ensure that x==xb will be decided. Any ideas? Best, Max -------- Original-Nachricht -------- > Datum: Mon, 18 Jul 2011 10:30:35 +0200 > Von: Guido Tack <[email protected]> > An: Max Ostrowski <[email protected]> > CC: [email protected] > Betreff: Re: [gecode-users] IIS using undoing > Hello Max, > > you may be able to turn this into a constraint problem that you can solve > using the Gecode search engines, but they are also copying the spaces under > the hood. The only thing they may do different from plain copying is > recomputation (see Sect. 7.2 in Modeling and Programming with Gecode). There > is no mechanism in Gecode to undo any changes to a variable domain. > > Cheers, > Guido > > On 18 Jul 2011, at 10:05, Max Ostrowski wrote: > > > Hello, > > > > i want to compute an "Irreducible Infeasible Set" (IIS) and some > derivatives. > > This means, given a set of contraints C that are infeasible i want to > find the source of infeasibility. > > I'm satisfied with a rather small (but not necessarily optimal) and fast > approach. > > A simple way of doing this would now be, trying to remove all single > constraints from the set C and see if it is still infeasible. If yes, we can > remove the constraint from the set. > > In Gecode i could do this using a lot of copies of the Space, always > posting the constraints again. > > Instead of posting them again i could also use reified constraints and > set all but one to true. > > But here i also have to copy the space, as i can not ? undo the setting > of a variable. > > So is there a clever way of doing this abusing the Gecode SearchEngine ? > (what i understood from the manual there is undoing instead of copying at > some points). > > > > > > > > The same thing i wanna do with a similar set C and a reified constraint > x. > > I wanna find the minimal (small) subset of C that the reified constraint > x is still decided (true or false does not matter). > > > > > > Thanks in advance for your proposals. > > > > Best, > > Max > > > > -- > > NEU: FreePhone - kostenlos mobil telefonieren! > > Jetzt informieren: http://www.gmx.net/de/go/freephone > > > > _______________________________________________ > > Gecode users mailing list > > [email protected] > > https://www.gecode.org/mailman/listinfo/gecode-users > > -- > Guido Tack, http://people.cs.kuleuven.be/~guido.tack/ > > > > > -- NEU: FreePhone - kostenlos mobil telefonieren! Jetzt informieren: http://www.gmx.net/de/go/freephone _______________________________________________ Gecode users mailing list [email protected] https://www.gecode.org/mailman/listinfo/gecode-users
