[gecode-users] Conditional constraints ?

[Wajid Hassan]

Thank you for sparing the time Guido, I will read the documentation.

BR/ Wajid



On Wed, Feb 22, 2012 at 1:07 AM, Guido Tack <tack at gecode.org> wrote:

> 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 <tack at gecode.org> 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/
>>
>>
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>
> --
> Guido Tack,
> http://www.csse.monash.edu/~guidot/
>
>
>
>
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