[gecode-users] Advisor on a ViewArray and index of assigned variable

[Valentin Lemière]

Hi,

Oh right a view is shared and could also be somewhere else than in my 
view array.

I get it now, thanks for taking the time to answer my questions.

Regards,
Valentin

On 11/10/2015 09:03 PM, Christian Schulte wrote:
>
> Hi,
>
> No, this is not at all feasible as I tried to explain: the view has 
> (and hence the advisor) has no idea that the view is stored in a view 
> array. Think of it as follows: the view might be stored in different 
> arrays by different propagators. So how could the view and hence the 
> advisor know which array we talk about?
>
> Cheers
>
> Christian
>
> --
>
> Christian Schulte, www.gecode.org/~schulte 
> <http://www.gecode.org/%7Eschulte>
>
> Professor of Computer Science, KTH, cschulte at kth.se 
> <mailto:cschulte at kth.se>
>
> Expert Researcher, SICS, cschulte at sics.se <mailto:cschulte at sics.se>
>
> *From:*users-bounces at gecode.org [mailto:users-bounces at gecode.org] *On 
> Behalf Of *Valentin Lemière
> *Sent:* Tuesday, November 10, 2015 05:20 PM
> *To:* cschulte at kth.se
> *Cc:* users at gecode.org
> *Subject:* Re: [gecode-users] Advisor on a ViewArray and index of 
> assigned variable
>
> Hi,
>
> I see, thanks for your answer.
>
> When an Advisor is used on a BoolView it stores the type of assignment 
> in the delta, which can be accessed with BoolView::one and ::zero.
>
> But couldn't an Advisor, when applied to a ViewArray, store the index 
> in the delta and then access it with ViewArray::index?
>
> With the index I can get the assigned value but not the other way around.
>
> It's not the case right now I understand, but do you think this is 
> something feasible?
>
> Regards,
>
> Valentin
>
> ------------------------------------------------------------------------
>
> *De: *"Christian Schulte" <cschulte at kth.se <mailto:cschulte at kth.se>>
> *À: *"Valentin Lemière" <valentin.lemiere at unicaen.fr 
> <mailto:valentin.lemiere at unicaen.fr>>, users at gecode.org 
> <mailto:users at gecode.org>
> *Envoyé: *Lundi 9 Novembre 2015 20:20:51
> *Objet: *RE: [gecode-users] Advisor on a ViewArray and index of 
> assigned variable
>
> Hi,
>
> An advisor subscribes to a particular variable implementation through 
> a view hence, the only information that is available by default is 
> which advisor is executed and what is the delta.
>
> Additional information – such as the position of an advisor in a view 
> array – must be explicitly stored in the advisor, there is no way 
> around it.
>
> Cheers
>
> Christian
>
> --
>
> Christian Schulte, www.gecode.org/~schulte 
> <http://www.gecode.org/%7Eschulte>
>
> Professor of Computer Science, KTH, cschulte at kth.se 
> <mailto:cschulte at kth.se>
>
> Expert Researcher, SICS, cschulte at sics.se <mailto:cschulte at sics.se>
>
> *From:*users-bounces at gecode.org <mailto:users-bounces at gecode.org> 
> [mailto:users-bounces at gecode.org] *On Behalf Of *Valentin Lemière
> *Sent:* Monday, November 9, 2015 04:56 PM
> *To:* users at gecode.org <mailto:users at gecode.org>
> *Subject:* [gecode-users] Advisor on a ViewArray and index of assigned 
> variable
>
> Hello everyone,
>
> I am a PhD. student and I am currently looking at Gecode to see if 
> it'll fit my needs.
>
> I need to implement a global constraint on a large number of boolean 
> variables. So I have extended from NaryPropagator with a view of type 
> BoolView.
>
> When a variable is assigned, the propagator infers some knowledge and 
> may assign other variable(s).
>
> To get the required information, I added an Advisor to each variable, 
> storing its index; so I can get it in the advise method and provide it 
> to the propagator.
>
> But this technique is too slow and creates too much advisors.
>
> So I tried adding an Advisor directly to the ViewArray; the advise 
> function is correctly called and I can still get whether the variable 
> was assigned a zero or a one with the delta.
>
> But I don't get the index information to find the actual assigned 
> variable.
>
> I looked for a static method of ViewArray to convert the delta to this 
> information but couldn't find one.
>
> Can an Advisor on a ViewArray get the index of the assigned variable?
>
> Or is there another way to deal with a large number of variables other 
> than an Advisor per variable?
>
> Regards,
>
> Valentin
>

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