[gecode-users] Remapping of BoolVar propagation conditions

[Vincent Barichard]

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
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Le 29 nov. 09 ? 17:34, Christian Schulte a ?crit :

> Hi,
>
> I am sorry but I do not understand Guido's answer. The reason why  
> Boolean
> propagation conditions are remapped is simple: we have many  
> propagators that
> are used both for Boolean as well integer views. Hence, both Boolean  
> as well
> as integer views need to have the same propagation conditions. As  
> there is
> no need to have anything but assigned as a condition for Boolean  
> variables,
> the integer conditions are mapped to assigned.
>
> Changing this will break all propagators that are used for integer  
> as well
> as Boolean variables.
>
> However, if you want to add a propagation condition to Boolean  
> variables
> that's fine. You only have to make sure that integer conditions are  
> mapped
> appropriately.
>
> If you really want to know whether a Boolean variable is assigned  
> 0/1 don't
> use propagation conditions but use advisors. See the Boolean  
> propagators
> such as NaryOr or Clause for an example.
>
> Christian
>
> -----Original Message-----
> From: users-bounces at gecode.org [mailto:users-bounces at gecode.org] On  
> Behalf
> Of Guido Tack
> Sent: Sunday, November 29, 2009 2:45 PM
> To: Vincent Barichard
> Cc: gecode list
> Subject: Re: [gecode-users] Remapping of BoolVar propagation  
> conditions
>
> Hi Vincent,
>
> for BoolVars, there are only two possible events, "assigned 0" and  
> "assigned
> 1", so I assume you wanted to add those so that your propagator is  
> only
> scheduled for particular assignments, not for the general PC_BOOL_VAL.
> The reason why we don't support these events is that we require  
> propagators
> to report when they are subsumed at the latest when all their  
> variables are
> assigned.  If a propagator only subscribed to the hypothetical  
> PC_BOOL_ONE,
> but the variable was assigned 0, the propagator would not be able to  
> report
> subsumption, and would remain in the system although it could be  
> removed.
> Note that this is an optimization, so if you want to change the  
> behavior,
> the system would still work as expected, it would just need more  
> memory in
> certain situations.  You should however check first if the  
> additional calls
> of the propagators are really a performance problem.
>
> Cheers,
> 	Guido
>
> Vincent Barichard wrote:
>
>> Hi,
>>
>> I would like to add a propagation condition to the BoolVar  
>> variables. I
> succeeded
>> to add this new propagation condition but when I tried to subscribe
> variables to
>> this new propagation condition, I discovered that all propagation
> conditions
>> for BoolVar are remapped to PC_BOOL_VAL.
>>
>> Why are they remapped ? Can I safely removed this mapping ?
>>
>> I found the remapping of the propagation condition in the file
> gecode/int/var-imp/bool.hpp.
>>
>> forceinline void
>> BoolVarImp::subscribe(Space& home, Propagator& p, PropCond,
>>                       bool process) {
>>   // Subscription can be used with integer propagation conditions,
>>   // which must be remapped to the single Boolean propagation  
>> condition.
>>   BoolVarImpBase::subscribe(home,p,PC_BOOL_VAL,assigned(),process);
>> }
>> forceinline void
>> BoolVarImp::cancel(Space& home, Propagator& p, PropCond) {
>>   BoolVarImpBase::cancel(home,p,PC_BOOL_VAL,assigned());
>> }
>>
>> Thank you for your help.
>>
>> Cheers,
>> Vincent
>>
>> Vincent Barichard         Universit? d'Angers (LERIA)
>> Tel: 02 41 73 52 06      D?partement Informatique
>> Fax: 02 41 73 50 73     H203
>>
>>
>> _______________________________________________
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>
>
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Vincent Barichard         Universit? d'Angers (LERIA)
Tel: 02 41 73 52 06      D?partement Informatique
Fax: 02 41 73 50 73     H203