[gecode-users] Reified Constraints do not propagate

[Guido Tack]

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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