[gecode-users] Consecutive instances of Gecode produce different results

[Christian Schulte]

Oh, I see. That means that there is most likely a bug (could also be ok) in
your own propagator.

Normally, a propagator must be monotonic: it never propagates more when it
is run on bigger variables domains. Or with other words: the smaller the
domains the more it propagates.

Some propagation algorithms do not follow this which might lead to
indeterminstic behavior as you observed. Check 22.9 in MPG.

But most likely it is a bug in your propagator.

Or do you use parallel search with several threads? This can also lead to
non-deterministic behavior.

Cheers
Christian

--
Christian Schulte, www.ict.kth.se/~cschulte/


> -----Original Message-----
> From: Pascal Francq (Mailing lists) [mailto:mailing-list at francq.info]
> Sent: Thursday, May 23, 2013 5:43 PM
> To: cschulte at kth.se
> Subject: Re: [gecode-users] Consecutive instances of Gecode produce
different
> results
> 
> I use two Gecode::IntVarArray variables I and v. The code for the
constraints and
> the branching is the following one :
> 
> // Maximal value <= 1
> rel(*this,1>=sum(v));
> 
> // Sum_(i)(2*v[i]-Sum_(j,j<>i)(I[i,j])>=0
> for(size_t i=0;i<4;i++)
> {
>    IntVar tmp[3];
>    size_t idx(0);
>    for(size_t j=0;j<4;j++)
>    {
>       if(i==j)
>          continue;
>       if(idx)
>          tmp[idx]=expr(*this,tmp[idx-1]-abs(I[i,j]));
>       else
>          tmp[idx]=expr(*this,-abs(I[i,j]));
>       idx++;
>     }
>     rel(*this, 0<=2*v[i]+tmp[idx-1]);
> }
> 
> // Call my own propagator
> choquetPropagator(*this,Test,v,I,Cost);
> 
> // Make the branch
> branch(*this,v,INT_VAR_SIZE_MIN(),INT_VAL_MIN());
> branch(*this,I,INT_VAR_SIZE_MIN(),INT_VAL_MIN());
> 
> 
> Le 23/05/13 17:23, Christian Schulte a écrit :
> > Could you tell us which constraints and which branchings you are using?
> >
> > Best
> > Christian
> >
> > --
> > Christian Schulte, Professor of Computer Science, KTH,
> > www.ict.kth.se/~cschulte/
> >
> >
> > -----Original Message-----
> > From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On
> > Behalf Of Pascal Francq (Mailing lists)
> > Sent: Thursday, May 23, 2013 4:59 PM
> > To: users at gecode.org
> > Subject: [gecode-users] Consecutive instances of Gecode produce
> > different results
> >
> > Hi,
> > I have a strange problem : I have a function that runs a Gecode
> > instance for a particular problem. When I call the function several
> > times, the result of the first run sometimes differs from those of the
other
> ones.
> > I have make some runs with valgrind, but I see nothing. Has anyone an
> > idea where to search ?
> > --
> > Dr. Pascal Francq
> > Belgium
> >
> > _______________________________________________
> > Gecode users mailing list
> > users at gecode.org
> > https://www.gecode.org/mailman/listinfo/gecode-users
> >
> 
> 
> --
> Dr. Pascal Francq
> Belgium