[gecode-users] different nr of solutions with and without GIST

Guido Tack tack at ps.uni-sb.de
Fri Jan 9 10:42:05 CET 2009

Gustavo Gutierrez wrote:
> I am experiencing almost the same problem. There is a difference in  
> the number of solutions when i run my problem instance with or  
> without gist. The difference with the case reported is that for me  
> the number of solutions reported by gist is really large compared to  
> the number of solutions of the command line search. In my case the  
> search without gist reports the right number of solutions.
> As i am working with a new constraint system i think this is caused  
> by some bug in my implementation, but the question is: if it is a  
> bug then both search strategies should exhibit it, am i right?

Not necessarily.  If it's due to non-monotonicity of a propagator,  
anything can happen - the shape and size of the tree might even depend  
on memory layout and other influences that are impossible to control.   
If the propagator is in addition not correct, also the number of  
solutions can differ substantially.
In your case, does Gist return solutions that shouldn't be accepted as  
solutions, or does it return solutions more than once?


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