[gecode-users] ExecStatus : what to return in case of no propagation

[Christian Schulte]

Hi Martin,

It doesn't matter, both works: ES_FIX means that the propagator is at
fixpoint wrt the current domain of the variables. ES_NOFIX differs only if
the propagator performs some domain changes which it does not in your case:
it means that the propagator is at fixpoint when it did not do any variable
domain modifications otherwise it is not and will be re-executed at some
point in time.

And yes, you should use advisors as they are more efficient: you save that
the propagator is actually scheduled and executed.

Cheers
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 Martin Mann
Sent: Thursday, April 04, 2013 2:11 PM
To: gecode user list
Subject: [gecode-users] ExecStatus : what to return in case of no
propagation


Hi Gecoders,

I have written a computationally expensive binary propagator that should be
triggered only if one of the two constrained domains is smaller a certain
threshold.

Currently, I am enforcing this behaviour by subclassing the propagator from

Gecode::BinaryPropagator<Gecode::Int::IntView,Gecode::Int::PC_INT_DOM>

and doing the following in my propagate function

//////////////////////////////////////////////////////////////////
propagate(Gecode::Space& home, const Gecode::ModEventDelta&) {
  // check if domain size limits are exceeded if (x0.size() > maxDomainSize
&& x1.size() > maxDomainSize)  {
  // domains are too large, dont propagate for now
  return Gecode::ES_FIX;
}
... normal propagation starts here
}
//////////////////////////////////////////////////////////////////

First question I have: do I have to return Gecode::ES_NOFIX or as I do
ES_FIX in case of no propagation?
Since I dont wont the propagator not to be called again until the domains
are shrinked, I assume this to be a virtual fix point, right?

Second question that came to me: is there a better way to get this domain
size specific call behaviour e.g. via Advisor implementation etc?


Thanks for your help,
Martin


-- 
Dr. Martin Mann, Postdoc assistant
Bioinformatics - Inst. of Computer Science
Albert-Ludwigs-University Freiburg
Tel: ++49-761-203-8254
Fax: ++49-761-203-7462
http://www.bioinf.uni-freiburg.de/~mmann/


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