On 21 Feb 2012, at 19:20, Wajid Hassan wrote: > Hi Guido, > > Thank you for the reply. > > // That is what the element constraint is used for (you'll find it in the > documentation). It works directly on variables, so you don't have to solve > the sub-problem on x first. > > I am not sure I follow your point. Let me clarify the question, there are two > integer variable arrays Array1[] and Array2[]. Both the arrays are > constrained in different ways individually. Then, as a last constraint > Array1[] needs to be constrained using the values assigned to Array2[]. So, > do u think the following constraint would work or not? > >> rel(*this, Array2[Array1[some_index].val()] + (something) <= >> Array2[another_index]); > > > It doesn't give any errors on compilation but I haven't finished the rest of > the model yet to be 100% sure if it works correctly or not.
No, that's not how it works, because when you model your problem, the value of Array1[some_index].val() is not yet known (an exception will be thrown at runtime). It also depends a lot on whether some_index and another_index are IntVars or simple int constants. If they are simple ints, the following may work: rel(*this, element(Array2, Array1[some_index]+(something)) <= Array2[another_index])); If they are IntVars, you need to decompose some more using element. Please read the documentation on element constraints, that should clarify things. Cheers, Guido > > Thank you in advance. > > Best regards, > Wajid > > On Mon, Feb 20, 2012 at 11:04 PM, Guido Tack <[email protected]> wrote: > On 21 Feb 2012, at 08:33, Wajid Hassan wrote: > >> Hi Christian, >> >> The problem in a nut shell is: >> >> I have two arrays of integer variables, Array1[x] and Array2[x]. I want to >> use the value assigned to the variables in Array1[] as an index of Array2[], >> something like this: >> >> rel(*this, Array2[Array1[x].val()] + (something) <= Array2[x+1]); >> >> Is there anything wrong with the above constraint or should this work? > > That is what the element constraint is used for (you'll find it in the > documentation). It works directly on variables, so you don't have to solve > the sub-problem on x first. > > Cheers, > Guido > > -- > Guido Tack, > http://www.csse.monash.edu/~guidot/ > > > _______________________________________________ > Gecode users mailing list > [email protected] > https://www.gecode.org/mailman/listinfo/gecode-users -- Guido Tack, http://www.csse.monash.edu/~guidot/
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