[gecode-users] Computing Variable Domains

[Guido Tack]

Sorry but I'm not sure I understand what you're trying to do.  Are you trying to precompute bounds on the domains of a and b given that there is a constraint a+b=c in your model?  We don't have specialised iterators for that kind of computation, and just running propagation (i.e. calling status once) will give you the same result.  You should only restrict the variables to reasonable initial domains (i.e., use some easy to compute upper and lower bounds). But you don't have to do the propagators' job.

Cheers,
Guido

On 13/08/2012, at 8:57 PM, Max Ostrowski <ostrowsk at cs.uni-potsdam.de> wrote:

> Thank you very much for the fast answer.
> I tried to play around with them but still face a lot of problems.
> 
> In the documentation http://www.gecode.org/doc-latest/reference/group__FuncIterRangesVirt.html it is written that
> "Iterators with virtual member functions have to be used when they are combined dynamically ..."
> The only base class i found is MinMax.
> 
> So how can i use the iterator dynamically.
> In the given example i have to know the type of the iterator used before.
> (To build the intersection of two Singletons for example)
> But if i want to build the intersection of two "domains" which could have been constructed in various ways (for example recursively),
> i need to have a general Base Type, right ?
> Is the Iter::Ranges thing still the right thing to use or is there something else.
> 
> Also i found only iterators for union/intersection etc...
> Given that you want to add two variables a and b with known domain (stored in a RangeList?), how do you compute the domain of the result.
> Is there any functionality for this or do i have to iterate through both lists of ranges and add them together to form a new list.
> 
> 
> I hope i made things clear, if not please ask.
> 
> 
> Best,
> Max
> 
> 
> On 08/10/2012 06:44 AM, Guido Tack wrote:
>> 
>> Hi,
>> 
>> here's some code that will do what you want:
>> 
>>       Iter::Ranges::Singleton si00(6,Int::Limits::max);
>>       Iter::Ranges::Singleton si10(Int::Limits::min,9);
>>       Iter::Ranges::Inter<Iter::Ranges::Singleton,Iter::Ranges::Singleton> 
>>         inter0(si00,si10);
>> 
>>       Iter::Ranges::Singleton si01(101,Int::Limits::max);
>>       Iter::Ranges::Singleton si11(Int::Limits::min,104);
>>       Iter::Ranges::Inter<Iter::Ranges::Singleton,Iter::Ranges::Singleton> 
>>         inter1(si01,si11);
>> 
>>       Iter::Ranges::Union<
>>         Iter::Ranges::Inter<Iter::Ranges::Singleton,Iter::Ranges::Singleton>,
>>         Iter::Ranges::Inter<Iter::Ranges::Singleton,Iter::Ranges::Singleton> > 
>>         u(inter0,inter1);
>> 
>>       IntVar a(*this,IntSet(u));
>> 
>> You can also use the n-ary variants of the iterators if you need to compute a union or intersection of more than two sets.
>> 
>> Cheers,
>> Guido
>> 
>> On 08/08/2012, at 9:41 PM, Max Ostrowski <ostrowsk at cs.uni-potsdam.de> wrote:
>> 
>>> Sorry for reposting an old question. I'm just cleaning up my code and noticed that i still not managed to use gecode's functionality to precompute domains of IntVar.
>>> So, given a constraint "(a>5 /\ a<10) \/ (a>100 /\ a<105)"
>>> I want to precompute the domain of "a".
>>> I'm simply not able to find out how the Ranges iterators are used.
>>> How to i create a range "5..inf" and a range "-inf..10"
>>> How do i create the intersection of both.
>>> And finally how to set the domain of IntVar x to this range then.
>>> 
>>> 
>>> I tried to grep the gecode code and the examples but was not able to find any.
>>> 
>>> Sorry again for reposting this, i'm ashamed.
>>> 
>>> Best,
>>> Max
>>> 
>>> 
>>> 
>>> 
>>> 
>>> The best is to look for examples in the code ;-) Just grep for it.
>>> 
>>> MinMax is nothing but a base-class for other classes and cannot be used 
>>> directly. Look for the iterators that take arrays as input, they will do what 
>>> you want.
>>> 
>>> Best
>>> Christian
>>> 
>>> --
>>> Christian Schulte, KTH, web.it.kth.se/~cschulte/
>>> 
>>> -----Original Message-----
>>> From: users-boun... at gecode.org [mailto:users-boun... at gecode.org] On Behalf Of 
>>> Max Ostrowski
>>> Sent: Thursday, July 21, 2011 10:49 AM
>>> To: users at gecode.org
>>> Subject: [gecode-users] Computing Variable Domains (Integer)
>>> 
>>> Hello everybody,
>>> 
>>> as variables in gecode need to have a domain, i want to compute the domain of 
>>> the variables automatically, given the constraints.
>>> I could also let the constraints restrict the domains of my variables, but as i 
>>> understood, this is similar to propagation and could take some time.
>>> There i want to restrict the domain manually for all unary constraints.
>>> So, given a constraint "(a>5 /\ a<10) \/ (a>100 /\ a<105)"
>>> the domain should be {6..9,101..104}.
>>> Therefore i wanted to use some Gecode classes to compute the 
>>> intersection/union/complement etc.. of the sets.
>>> Am i right that i can use the Int::Iter::Ranges classes for this?
>>> And second, how do they work?
>>> So in this case, i would create a 
>>> 
>>> IntSet a1(Gecode::Iter::Ranges::MinMax(5+1,Int::Limits::max));
>>> IntSet a2(Gecode::Iter::Ranges::MinMax(Int::Limits::min, 10-1));
>>> 
>>> And them somehow the intersection of this.
>>> But i was neither able to initialize a set with a Range, nor to combine Ranges 
>>> recursively.
>>> 
>>> So, how do i do this using the helping classes of gecode.
>>> 
>>> Best,
>>> Max
>>> _______________________________________________
>>> Gecode users mailing list
>>> users at gecode.org
>>> https://www.gecode.org/mailman/listinfo/gecode-users
>> 
> 
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