[gecode-users] Getting domain values after posting

[Christian Schulte]

Hi,

propagation in Gecode is not automatic (some simple cases are done
immediately as you report, others are not). This is not a bug but an
essential feature (this is what enables batch recomputation). In order to
actually perform constraint propagation one has to invoke the
status(unsigned int&) member function of a space. Not only will that perform
constraint propagation but it also reports about the status of a space: is
it failed, solved, does it require branching. So in your case just add
something along the lines:
	unsigned int alt;
	(void) status(alt); // Discard status result

After that you will be able to observe the result of constraint propagation.

Christian


--
Christian Schulte, http://web.imit.kth.se/~schulte/



-----Original Message-----
From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf
Of Efstratios Kalogirou
Sent: Tuesday, March 28, 2006 5:35 PM
To: users at gecode.org
Subject: [gecode-users] Getting domain values after posting


Hi all, 

I am trying to get the remaining (valid) values and the size of the domain
of a variable after posting some constraints (assuming that due to the
constraints some values inside the domain are no longer valid). It seems
that everything is fine when I don't use any BoolVar to wrap the contraint.
For example: 

IntVarArray q(this,1,0,10);
post(this,q[0]==3);
cout<<"The size of the domain is now "<<q[0].size()<<endl;

In the above case the size of the domain is indeed 1 and the solution is
correctly the value 3. 

But things are different when I try to wrap the equality constraint in a
BoolVar:

IntVarArray q(this,1,0,10);
BoolVar wrapper(this,0,1);
rel(this,q[0],IRT_EQ,3,wrapper,ICL_BND);
post(this, wrapper==1);
cout<<"The size of the domain is now "<<q[0].size()<<endl;

In the latter example I get again the corrent solution 3 but after posting
the constraint the size of the domain remains 11 and doesn't shrink to 1 as
I would expect. 

Since I am solving problems using the second way I am wondering if there is
a way to shrink the domain of the variable after posting as showed in the
second example. Also how can I get all the valid values of the domain of a
variable after posting? I assume this can be done by using iterators but I
am not certain how exactly to relate the iterator with the IntVar or the
IntSet that represents the variable, so any enlightening on that, would be
highly appreciated. 

Best, 
Stratos Kalogirou