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 

----- Mail original -----

De: "Christian Schulte" <cschu...@kth.se> 
À: "Valentin Lemière" <valentin.lemi...@unicaen.fr>, users@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 

Professor of Computer Science, KTH, cschu...@kth.se 

Expert Researcher, SICS, cschu...@sics.se 





From: users-boun...@gecode.org [mailto:users-boun...@gecode.org] On Behalf Of 
Valentin Lemière 
Sent: Monday, November 9, 2015 04:56 PM 
To: users@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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