[gecode-users] propagator - gist problem

Alberto Delgado trosky99 at gmail.com
Wed Nov 19 16:36:07 CET 2008

I tried ES_NOFIXED and it didn't work either but i'd like to be sure that
what i understand about each ExecStatus of a propagator is correct:

ES_SUBSUMED = The propagator can be entailed from the store so it is not
necessary any more.
ES_FAILED = The propagator failed.  A variable has an empty domain or some
specific condition is fulfilled and according to me it is not possible to
reach a feasible solution from here and i want the space to fail.
ES_FIX = The propagator can't prune any more  values from the domains (has
reached a fix point) but it is not entailed yet.
ES_NOFIX = The propagator hasn't reached a fix point yet so I want it to be
enqueued and run again before the space reaches a fix point.
ES_OK = No clue.

The problem i have with Gist occurs when the propagator fails,  it seems
like i return fail but the space somehow doesn't fail at all.



On Wed, Nov 19, 2008 at 3:41 PM, Guido Tack <tack at ps.uni-sb.de> wrote:

> Alberto Delgado wrote:
> I'm  implementing a propagator and it works OK when i search for a solution
> with Search  but when it comes to Gist an exception is thrown:
> Space::clone: Attempt to invoke operation on failed space.
> This is what i do to modify the domain of the variable and check whether
> the modification is valid:
>   ModEvent me =  x1.gq(home,constantValue);
>   if (me_failed(me)){
>    return ES_FAILED;
>    }
>   return ES_FIX;
> I can assure  that the propagator returns ES_FAILED (a std::cout before the
> return ES_FAILED line) when it has to and doing some extra tests i found out
> that if instead of modifying the domain of x1 i just check whether the
> variable's domain is empty  the exception disappears.
> Are you sure that your propagator computes a fixed point?  If not, try
> returning ES_NOFIX and see if the problem goes away.
> Cheers,
> Guido
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