[gecode-users] Gecode/J: nary contraints + propagator modification event

[Guido Tack]

Hi.

Guillaume Richaud wrote:
> I am looking for information about nary constraints and propagator  
> modification event in Gecode/J.
> Is there any example or tutorial about a propagator using  
> modification event and propagation condition to make specific  
> filtering?
>
> For example: if I implement a constraint with three variables and I  
> want to know why propagator requires to be re-executed. How to  
> detect which kind of event happened on the variables' domain  
> involve in the constraint ?

This information is not available in Gecode/J. We only provide a  
limited interface for propagators through the Java binding. Even in  
the C++ version, the only information you can always get is the  
combined modification event for all variables. So you don't know  
which variable was changed, and in which way.
However, you can find that out in the propagator in linear time by  
scanning all the variables. You only need to store the old domain (or  
enough of it, depending on what events you're interested in).

Cheers,
	Guido

-- 
Guido Tack
Programming Systems Lab, Saarland University, Germany
http://www.ps.uni-sb.de/~tack



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