[Gecode] Announcement: FS constraints prototype

[duchier at ps.uni-sb.de]

Guido Tack <tack at ps.uni-sb.de> writes:

>    - S_1\supseteq S_2\cap S_3
>    - S_1\subseteq S_2\cup S_3

er... isn't that backwards? it should be:

      S_1\subseteq S_2\cap S_3
      S_1\supseteq S_2\cup S_3

> The model that we think of for cardinality at the moment is the following: We 
> want to introduce an FD variable together with every FS variable and post a 
> propagator that is subscribed to both and implements the cardinality 
> constraints.

That's essentially the way it is done in Mozart: each FS variable
keeps track of min/max for cardinality. FS.card simply posts a
propagator between the FS variable and a FD variable that propagates
these bounds both ways.

Please, keep a similar design.  We certainly don't want to introduce
cardinality variables and propagators for _all_ sets.

> The reason for separating the cardinality and the set variable 
> is the limited number of modification events: We just could not signal a 
> change of cardinality in addition to the MEs for lower and upper
> bound.

Could you elaborate on this paragraph?  I am not as familiar with
gecode internals as you are :-(

Cheers,

-- 
Denys Duchier - Équipe Calligramme - LORIA, Nancy, France