[gecode-users] Problem with constraint

[Ujhelyi Zoltan]

Hello,

thank you for your reply.

I understand the problem stated here, but I would like to ask whether  
there is a solution to add a constraint like that to a Boolean  
Expression with the domain consistent propagation (ICL_DOM).

I did not found any possibilities for that looking in the Gecode/J  
API, but it would help a lot for our project.

Thank you,
Ujhelyi Zoltán
On 2008.08.11., at 11:34, Guido Tack wrote:

> Could you please post to the mailing list? Thanks. Guido
>
> Am 11.08.2008 um 11:22 schrieb Ujhelyi Zoltan:
>
>> Hello,
>>
>> thank you for your reply.
>>
>> I understand the problem stated here, but I would like to ask  
>> whether there is a solution to add a constraint like that to a  
>> Boolen Expression with the domain consistent propagation (ICL_DOM).
>>
>> I did not found any possibilities for that looking in the Gecode/J  
>> API, but it would help a lot for our project.
>> Thank you,
>> Zoltán Ujhelyi
>> On 2008.08.11., at 9:03, Guido Tack wrote:
>>
>>> Hi.
>>>
>>> As you've already found out, you have to use domain consistent  
>>> propagation (ICL_DOM) to get the result you want.  You should be  
>>> able to use post(space, new Expr(space.variable1), IRT_EQ, new  
>>> Expr(space.variable2), ICL_DOM) to get the desired result.  I'm  
>>> not 100% sure, but I think your solution that uses e=variable1- 
>>> variable2, e=0 doesn't work because only the e=0 is propagated to  
>>> domain consistency, while e=variable1-variable2 still only  
>>> achieves bounds consistency.
>>>
>>> Cheers,
>>> 	Guido
>>>
>>> Ujhelyi Zoltan wrote:
>>>
>>>> Hello again,
>>>>
>>>> I have been experimenting with the questions raised in my  
>>>> previous mail.
>>>>
>>>> I created a small Gecode space to be able to test the problem in a
>>>> smaller scale, where I did use two variables (variable1, variable2,
>>>> both IntVars with the domain {0,5}) and three constraints:  
>>>> variable1
>>>> equals variable2, and variable2 cannot have the values 2 and 4.
>>>>
>>>> In all of my tests the latter two constraints are described like  
>>>> that:
>>>>
>>>> post(space, new BExpr(space.variable1, IRT_NQ, 2));
>>>> post(space, new BExpr(space.variable1, IRT_NQ, 4));
>>>>
>>>> For the third constraint I had several tries. When I was using the
>>>> rel() clause to write the constraint, I got the expected result:
>>>>
>>>> Variable #1: {0..1,3,5}
>>>> Variable #2: {0..1,3,5}
>>>>
>>>> But when using a similar construct I would like to use in the  
>>>> static
>>>> verifier, I got no result for the second variable, it can has all
>>>> values from it's domain.
>>>>
>>>> post(space, new BExpr(space.variable1, IRT_EQ, space.variable2));
>>>>
>>>> Reading about different propagators, I have been able to get the
>>>> expected result with the use of the ICL_DOM propagator, but only  
>>>> if I
>>>> was posting the constraint directly, like that:
>>>>
>>>> post(space, new Expr(space.variable1), IRT_EQ, new
>>>> Expr(space.variable2),org.gecode.GecodeEnumConstants.ICL_DOM);
>>>>
>>>> But if I tried to translate the a BExprs to that form, I did not
>>>> succeed:
>>>>
>>>> 	    Expr expression = new Expr(new
>>>> Expr(space.variable2).minus(space.variable1));
>>>> 	    post(space, new Expr(expression), IRT_EQ, 0,
>>>> org.gecode.GecodeEnumConstants.ICL_DOM);
>>>>
>>>> Can you tell me a way how to enable this strong ICL_DOM propagators
>>>> meanwhile using the BExpr form, if it is possible? It would help  
>>>> our
>>>> project a lot, it would simplify it's code.
>>>>
>>>> Thank you for your help,
>>>> Zoltán Ujhelyi
>>>> On 2008.08.09., at 18:30, Ujhelyi Zoltan wrote:
>>>>
>>>>> Hello all,
>>>>>
>>>>> we are currently trying to build a static checker system on top of
>>>>> Gecode/J 2.1.1. (in an Eclipse environment), and we have found an
>>>>> interesting case.
>>>>>
>>>>> In order to allow us greater flexibility we try to use the  
>>>>> Expression
>>>>> API (it allows us to build constraints in a hierarchical manner).
>>>>>
>>>>> I was testing the implementation, and found an interesting final
>>>>> result: there were to IntVars, which were supposed to be the  
>>>>> same, did
>>>>> not have the same final ranges: one of them had {2,4}, but the  
>>>>> other
>>>>> had {2,3,4}. I tried to trace back the code to look whether the
>>>>> constraints were wrong or not, and found the following expression
>>>>> building term:
>>>>>
>>>>> BExpr expression = new BExpr(new Expr(variable1),relation, new
>>>>> Expr(variable2));
>>>>>
>>>>> Tracing the variables variable1 was a new variable, it hadn't been
>>>>> constrained yet, while variable2's domain had been limited to the
>>>>> values 2 and 4 (and they were the variables mentioned before in  
>>>>> this
>>>>> letter), while the relation had the value IRT_EQ.
>>>>>
>>>>> I tried a post of the expression right after it's construction  
>>>>> to see
>>>>> whether it helps or not:
>>>>> org.gecode.Gecode.post(space, expression);
>>>>>
>>>>> It did not solve the problem, but when I replaced the post  
>>>>> method to
>>>>> the following rel call, the constraint handling was working as I
>>>>> expected it before.
>>>>>
>>>>> rel(space, variable1, IntRelType.IRT_EQ, variable2);
>>>>>
>>>>> I would like to know, whether this phenomenon is the intentional
>>>>> (maybe I do not understand something under the hood), or not.  
>>>>> And if
>>>>> you could tell me a way to avoid it, I would be very glad.
>>>>>
>>>>> Thank you very much in advance for your help,
>>>>> Zoltán Ujhelyi
>>>>> _______________________________________________
>>>>> Gecode users mailing list
>>>>> users at gecode.org
>>>>> https://www.gecode.org/mailman/listinfo/gecode-users
>>>>
>>>>
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>