[gecode-users] Remapping of BoolVar propagation conditions

[Christian Schulte]

Actually, what Guido and me tried to say is the following: conceptually,
Gecode should have two Boolean views, say BoolView and BoolAsAnIntView. The
former does not need rewriting and most propagators using Boolean views
should use this one. The latter must use rewriting to map integer
propagation conditions to the single supported Boolean propagation
condition.

Then there are integer propagators which we also want to use on Boolean
views (these are few: the extensional ones, including element and sequence).
These propagators should use BoolAsAnIntView including rewriting. All other
- true Boolean propagators should use the real BoolView.

So what you might want to do is to have these two different views, one with
and one without rewriting! Everything will work just fine.

Christian

-----Original Message-----
From: Vincent Barichard [mailto:Vincent.Barichard at univ-angers.fr] 
Sent: Tuesday, December 01, 2009 6:22 PM
To: Guido Tack
Cc: Christian Schulte; 'gecode list'
Subject: Re: [gecode-users] Remapping of BoolVar propagation conditions

Hi Guido,

That was my first thought. But I didn't understand why this remapping  
was there. Christian said in a previous mail that removing the mapping  
will break all propagators that are used for integer as well as for  
boolean variables! If I pass the pc unchanged, will it break something  
in Gecode ? I don't want to break something, I would like to add  
safely my piece of code.

If removing it doesn't break anything, will this mapping be still  
there in the future versions ?

Thank you again, I really appreciate the time you spent to answer my  
questions :)

Cheers,
Vincent

Le 1 déc. 09 à 16:30, Guido Tack a écrit :

> Hi Vincent,
>
> the rewriting is currently done in int/var-imp/bool.hpp.  Just  
> remove the rewriting there and pass the pc unchanged, add rewriting  
> to all the normal Gecode BoolView classes, and then add your own  
> BoolView class that doesn't rewrite.
>
> Cheers,
> 	Guido
>
> Vincent Barichard wrote:
>
>> Dear Christian,
>>
>> Thank you very much for your mail. I'm sorry, I don't understand  
>> your answer. Why having other BoolView classes will
>> help me ? I added member functions in the BoolViews classes. I  
>> didn't change the existing ones,
>> I only added member functions which notify the ME_BOOL_SAME event.
>>
>> In my own propagator (let's call it M) I call the recently added  
>> functions in the BoolViews. So the ME_BOOL_SAME
>> event is sent.
>>
>> I also modified one propagator of Gecode (let's call it P') and  
>> make it subscribe to the PC_BOOL_SAME propagation condition (I only  
>> added "x1.subscribe(home, *this, PC_BOOL_SAME)" in constructor).
>> In the "propagate" function of P' I added instructions which are  
>> only relevant if a ME_BOOL_SAME event has been sent before.
>>
>> So when M is woke up (because it subscribe to PC_BOOL_VAL  
>> propagation condition) it may call the new member functions in the  
>> BoolViews classes which sent the ME_BOOL_SAME event. I would like  
>> that propagators which subscribe to the PC_BOOL_SAME propagation  
>> condition and only these ones, be scheduled to wake up (for example  
>> P' will be scheduled if it shares a variable with M). As no  
>> assignment has been made by the M propagator, I don't want that  
>> other propagators wake up except if a ME_BOOL_VAL event has been  
>> sent from elsewhere.
>>
>> Unfortunately, as all propagation condition subscribings for  
>> Boleans variables are remapped to PC_BOOL_VAL, P' will not awake if  
>> a ME_BOOL_SAME event is sent.
>>
>> May have I another choice but to use the ME_BOOL_VAL event instead  
>> of ME_BOOL_SAME in my new member functions of the BoolView  
>> classes ? As a result, all propagators will be awaken even if they  
>> can't propagate removal, indeed no assignment has been made.
>>
>> Don't hesitate to ask me if I'm not clear enough.
>>
>> Cheers,
>> Vincent
>>
>> Le 30 nov. 09 à 16:35, Christian Schulte a écrit :
>>
>>> Actually what you have to do is the following: you define two  
>>> classes for
>>> Boolean views, one that rewrites its propagation conditions and  
>>> the other
>>> one that does not. Then your propagators can use the views without  
>>> rewriting
>>> while the other propagators can use the variables with rewriting.
>>>
>>> Christian
>>>
>>> --
>>> Christian Schulte, www.ict.kth.se/~cschulte/
>>>
>>>
>>> -----Original Message-----
>>> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org]  
>>> On Behalf
>>> Of Vincent Barichard
>>> Sent: Monday, November 30, 2009 9:33 AM
>>> To: Christian Schulte
>>> Cc: 'Guido Tack'; 'gecode list'
>>> Subject: Re: [gecode-users] Remapping of BoolVar propagation  
>>> conditions
>>>
>>> Hi,
>>>
>>> Thank you both for your answers. As I don't want to break all  
>>> propagators
>>> that are used for integer as well as boolean variables, I see no  
>>> choice but
>>> to use PC_BOOL_VAL.
>>>
>>> Maybe one of you may see another way ? I make new functions on  
>>> Boolean
>>> variables (and associated views) which don't set domain to 1 or 0  
>>> (I copied
>>> "ModEvent  BoolVarImp::one_none(Space& home)" and removed the  
>>> unwanted
>>> instructions). These functions notify new events (called  
>>> ME_BOOL_SAME in
>>> bool.vis file (see attached file)). I mapped this new event to the
>>> PC_BOOL_SAME propagation condition.
>>>
>>> Now I change an existing propagator (like the "Or" propagator),  
>>> and I want
>>> it to be awaken when ME_BOOL_SAME is emitted. As the variable is  
>>> not yet
>>> assigned, I didn't want to emit the ME_BOOL_VAL event because I  
>>> didn't want
>>> to wake up propagators which only subscribed to the PC_BOOL_VAL  
>>> condition.
>>>
>>> So during propagation, I call my new functions on Boolean  
>>> variables, the
>>> ME_BOOL_SAME event is sent and propagators which subscribe to the
>>> PC_BOOL_SAME condition are wake up. Other propagators are not  
>>> awaken (except
>>> if a ME_BOOL_VAL event has also been sent). Is it possible ?
>>> Should I use ME_BOOL_VAL ? If I use ME_BOOL_VAL other propagators  
>>> will be
>>> awaken for nothing.
>>>
>>> Thanks for your help.
>>>
>>> Cheers,
>>> Vincent
>>
>> Vincent Barichard         Université d'Angers (LERIA)
>> Tel: 02 41 73 52 06      Département Informatique
>> Fax: 02 41 73 50 73     H203
>>

Vincent Barichard         Université d'Angers (LERIA)
Tel: 02 41 73 52 06      Département Informatique
Fax: 02 41 73 50 73     H203