[gecode-users] LDSB : value symmetry on subset of branching variables ?

[Guido Tack]

On 23/04/2013, at 0:59 , Martin Mann <mmann at informatik.uni-freiburg.de> wrote:

> 
> Hi Gecoders,
> 
> a question concerning LDSB search breaking value symmetry.
> 
> I have a CSP where the branching is done on a set of variables X = X_1 + X_2 composed from two other sets X_1 and X_2.
> 
> I have different value symmetries for X_1 and X_2 that I want to impose.
> 
> As far as I see, I can only post the symmtries for a "full" branching.

Yes.

> Thus, if I want to enforce different symmetry breakings for X_1 and X_2, I have to split my branching into two successive branchings right? If so, this might weaken the search compared to branching on whole X (which is hopefully compensated by the symmetry breaking).
> 
> Or is there another way around it to specify for which variables what symmetry object is to be applied?

Just a workaround, but if you can "shift" the variables in one array, say X2,  so that their domains are disjoint from X1, then you could express this as one single symmetry.

Cheers,
Guido

-- 
Guido Tack,
http://www.csse.monash.edu/~guidot/



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