[gecode-users] Reification of the extensional constraint

[Guido Tack]

Hi,

you're right that you'd have to implement your own propagator for that.  Before you do that you should check if you actually need full reification (i.e. b <-> c) or if an implication would be enough (b -> c).  In the latter case, you don't need to implement the negation of c (where c is your extensional constraint).

If you implement the full version, negating a DFA is (in principle) easy, just make all accepting states rejecting and all rejecting states accepting.  In the Gecode representation the rejecting states aren't represented directly so you'll have to work around that a bit.

Cheers,
Guido

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



On 14 Jun 2014, at 8:35 pm, Amina Kemmar <kemmar.amina at gmail.com> wrote:

> Hi all,
> 
> I want to use a reification version of the extensional constraint, but I think that it is not implemented in Gecode.
> The chapter 24 explains how to implement a reification version of a constraint, I understand that we need the negation of the automata DFA. So, I want to know if there is an easy way to do this with extensional constraint? If you have any details about this, it will be very helpful for me.
> 
> Thanks.
> 
> Best regards,
> ---
> Amina
> 
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