[gecode-users] Symbolic Constraints - fd_relation contraint in Gecode?

[Denys Duchier]

Pedro Salgueiro <pds at di.uevora.pt> writes:

> Translating the large domain to a smaller one is a good idea, the
> problem is that besides I need to use the extensional constraint to make
> sure that the values belong to some matrix,

use extensional on the translated domains

> I also have to apply
> constraints to some of the values individual values of the tuple, based
> on the values of the large domain. So, if I translate the domain to a
> smaller one, then I have no way to apply such constraints.

yes you do: apply the constraint on de-translated versions of the vars

> For instance, let's suppose I have the following matrix:
>
> matrix={{9900, 1234, 2349} 
>         {9901, 2345, 5678}}
>
> wich will be translated to:
>
> translated_matrix={{0,1,2,3}
> 	           {4,5,6,7}}

let's say:

translated_matrix={{0,1,2}
 	           {3,4,5}}

so that the number of values actually correspond ;-)

> Then I will apply an extensional constraint to make sure that the
> variables C={X1,X2,X3} and C1={Y1,Y2,Y3} belongs to translated_matrix.

you use extensional on the translated matrix.

> Then I need to apply constraints that relate individual values on each
> of the tuple, such as
>
> Y1 - X1 < 10

I write A=<B1,B2,...,Bn>[I] for the element constraint.
Constrain 2 new variables XX1 and YY1 as follows:

XX1 = <9900,1234,2349,9901,2345,5678>[X1]
YY1 = <9900,1234,2349,9901,2345,5678>[Y1]

XX1 and YY1 are the de-translated versions of X1 and Y1, and you can
pose the constraint:

YY1 - XX1 < 10

> About the element constraint, I didn't got that one.

I hope the above example clears it up for you.

Cheers,

--Denys