[gecode-users] Reified Constraints do not propagate

[Guido Tack]

Hi,

I just added a fix to the svn trunk for the case of a reified equality between an IntVar and an int.  The default ICL for that case is now ICL_DOM (consistent with just using rel directly).

Other cases (e.g. equality between two variables) may still ignore the ICL, but we'll have a look at that, too.

Cheers,
Guido

-- 
Guido Tack
http://www.csse.monash.edu/~guidot/



On 13/04/2012, at 9:17 PM, Max Ostrowski wrote:

> Thanks and sorry for bugging you again.
> 
> I tried to analyze the minimodel code.
> I think that posting LinExpr instead of LinRel won't change the problem, right?
> So is there any interface so that one can still use the very handy LinExpr class?
> I do parse some quite complicated formulas and want to post a linear() constraint.
> LinExpr as far as I understood, optimizes this formula and reformulates it to fit into the form that is needed for the linear constraint.
> Is there a way to get this linear constraint out of it again to post it manually and preserve the ICL?
> 
> Or do i have to generate the linear constraint (array of variables and numbers) myself to get the full propagation power. Is there a logical reason why the ICL is lost during this "translation"?
> 
> Best,
> Max
> 
> On 04/10/2012 01:19 PM, Christian Schulte wrote:
>> 
>> Maybe, not so clear yet. We will change reification for the next major release and might at that time also think how to fix passing the consistency level.
>>  
>> For the time being you should stick to what Guido has suggested.
>>  
>> Christian
>>  
>> --
>> Christian Schulte, www.ict.kth.se/~cschulte/
>>  
>> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On Behalf Of Max Ostrowski
>> Sent: Tuesday, April 10, 2012 12:42 PM
>> To: Guido Tack
>> Cc: users at gecode.org
>> Subject: Re: [gecode-users] Reified Constraints do not propagate
>>  
>> Thank you very much for the insight.
>> Unfortunately this could be a problem,
>> as i have to change my data structures.
>> 
>> Will this be fixed in future versions?
>> 
>> Best,
>> Max
>> 
>> On 04/10/2012 12:32 PM, Guido Tack wrote:
>> This is a current shortcoming of the minimodel library.  For some linear constraints (such as x==5 in this case) the IntConLevel is ignored.  To get the full propagation, you have to post the constraint directly, like this:
>>  
>> Gecode::rel(*test, test->x_[1], IRT_EQ, 5, test->b_[1], ICL_DOM);
>>  
>> Cheers,
>> Guido
>>  
>> On 10 Apr 2012, at 19:20, Max Ostrowski wrote:
>> 
>> 
>> I have a small example where i do not understand why no propagation takes place.
>> 
>> test is a pointer to the space instance
>> x_ is an array of 10 IntVars(0,10)
>> b_ is an array of 2 BoolVars(0,1)
>> 
>> 
>>     LinRel rel1(test->x_[0],IRT_EQ,5);
>>     rel1.post(*test,true,ICL_DEF);
>> 
>>     Gecode::distinct(*test,test->x_,ICL_DEF);
>> 
>>     LinRel rel2(test->x_[1],IRT_EQ,5);
>>     Gecode::rel(*test, rel2 == test->b_[1],ICL_DEF);
>> 
>>     test->status();
>>     if (test->failed())
>>         std::cout << "Failed" << std::endl;
>>     std::cout << test->x_ << std::endl;
>>     std::cout << test->b_ << std::endl;
>> 
>> 
>> So i post das one of my elements x_[0] is 5, and all elements are distinct.
>> Now i have a reified constraint that x_[1] == 5.
>> The distinct constraint removes 5 from he domain of x_[1],
>>  but the propagator does not fire.
>> The result is:
>> {5, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}, {0..4,6..10}}
>> {[0..1], [0..1]}
>> 
>> Even with ICL_DOM the boolean variable is not touched if values are removed from the domain.
>> Also i think this could be easily done with "Advisors" ?
>> I have no experience with this, so my question:
>> Is this behavior the desired one?
>> Can this be changed if i have reifications like mine where i compare to constants?
>> 
>> Thanks a lot,
>> 
>> Max
>> _______________________________________________
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>>  
>> -- 
>> Guido Tack,
>> http://www.csse.monash.edu/~guidot/
>>  
>>  
>>  
>>  
> 
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