[gecode-users] Propagating to Fixpoint

[Guido Tack]

Without looking at the details: Do you check the return value of IntView::lq?  The view functions are not meant to be used in models. If lq returns failure, you have to check that yourself, or the space won't be failed.

Cheers,
Guido

-- 
Guido Tack


On 23/08/2012, at 13:20, Max Ostrowski <ostrowsk at cs.uni-potsdam.de> wrote:

> Actually its quite complicated.
> I'm currently debugging and have 60 constraints written on paper that have this effect.
> Two of them are actually not reified constraints but directly using IntView::lq(constant)
> 
> I can give you a description where it happens in my system, but it will be a mess for you to write simplified code that reproduces this.
> 
> Actually given two spaces original1 and original2 that are equal,
> variables are constraint like this:
> posx(6)=[0..185]
> posx(5)=[0..190] posx(4)=[0..142] posx(3)=[0..158] posx(2)=[0..113]
> posx(1)=[0..157]
> 
> 
> 
> all
> reified constraints are posted with free boolean variables, using
> 
> 
> 
> linear(*this, intArgs, intVarArgs, r,0,b_[boolvar],ICL_DEF);
> 
> Now i set the boolean variables accordingly, always doing propagation (calling status()) after each single posting
> 
> To
> original1 false ((-1 $* posx(3))+posx(1))$<=0
> To original1 false ( 10+(-1 $* posx(6))+posx(5))$>0
> To original1 false ( 58+(-1 $* posx(5))+posx(4))$>0
> To original1 true posx(6)<=69                            // this is no reified constraint, but just posted IntView(posx(6)).lq(69)
> To original1 false ( 43+(-1 $* posx(6))+posx(1))$>0
> To original1 false ((-1 $* posx(5))+posx(2))$<=0
> To original1 true ((-1 $* posx(1))+posx(3))$<=0
> To original1 true ((-1 $* posx(4))+posx(3))$<=0
> To original1 false ( 42+(-1 $* posx(5))+posx(3))$>0
> To original1 false ( 42+(-1 $* posx(6))+posx(3))$>0
> To original1 true ( -42+(-1 $* posx(3))+posx(1))$<0
> To original1 true ( -15+(-1 $* posx(6))+posx(1))$<0
> To original1 true ( 58+(-1 $* posx(1))+posx(4))$>0
> To original1 true ( 42+(-1 $* posx(1))+posx(3))$>0
> To original1 false ((-1 $* posx(1))+posx(2))$<=0
> To original1 true ((-1 $* posx(6))+posx(1))$<=0
> To original1 true ((-1 $* posx(5))+posx(1))$<=0
> To original1 true ( -10+(-1 $* posx(5))+posx(1))$<0
> To original1 true ((-1 $* posx(2))+posx(1))$<=0
> To original1 false ( 43+(-1 $* posx(2))+posx(1))$>0
> To original1 true ( -28+(-1 $* posx(1))+posx(6))$>0
> To original1 false ( 28+(-1 $* posx(6))+posx(1))$>0
> To original1 false ( -43+(-1 $* posx(1))+posx(2))$<0
> To original1 true ( -58+(-1 $* posx(4))+posx(1))$<0
> To original1 true posx(1)<=29                          // this is no reified constraint, but just posted IntView(posx(1)).lq(29)
> To original1 false ((-1 $* posx(1))+posx(4))$<=0       // lets call this constraint X
> 
> Now this space is failed.
> 
> Something similar with the second space, but posting nr. 5 is different.
> 
> To original2 false ((-1 $* posx(3))+posx(1))$<=0
> To original2 false ( 10+(-1 $* posx(6))+posx(5))$>0
> To original2 false ( 58+(-1 $* posx(5))+posx(4))$>0
> To original2 false ((-1 $* posx(1))+posx(4))$<=0       // this is constraint X, it is now posted on this position, no longer as the last constraint anymore
> To original2 true posx(6)<=69                          // this is no reified constraint, but just posted IntView(posx(6)).lq(69)
> To original2 false ( 43+(-1 $* posx(6))+posx(1))$>0
> To original2 false ((-1 $* posx(5))+posx(2))$<=0
> To original2 true ((-1 $* posx(1))+posx(3))$<=0
> To original2 true ((-1 $* posx(4))+posx(3))$<=0
> To original2 false ( 42+(-1 $* posx(5))+posx(3))$>0
> To original2 false ( 42+(-1 $* posx(6))+posx(3))$>0
> To original2 true ( -42+(-1 $* posx(3))+posx(1))$<0
> To original2 true ( -15+(-1 $* posx(6))+posx(1))$<0
> To original2 true ( 58+(-1 $* posx(1))+posx(4))$>0
> To original2 true ( 42+(-1 $* posx(1))+posx(3))$>0
> To original2 false ((-1 $* posx(1))+posx(2))$<=0
> To original2 true ((-1 $* posx(6))+posx(1))$<=0
> To original2 true ((-1 $* posx(5))+posx(1))$<=0
> To original2 true ( -10+(-1 $* posx(5))+posx(1))$<0
> To original2 true ((-1 $* posx(2))+posx(1))$<=0
> To original2 false ( 43+(-1 $* posx(2))+posx(1))$>0
> To original2 true ( -28+(-1 $* posx(1))+posx(6))$>0
> To original2 false ( 28+(-1 $* posx(6))+posx(1))$>0
> To original2 false ( -43+(-1 $* posx(1))+posx(2))$<0
> To original2 true ( -58+(-1 $* posx(4))+posx(1))$<0
> To original2 true posx(1)<=29                                        // this is no reified constraint, but just posted IntView(posx(1)).lq(29)
> 
> This Space is not failed
> 
> 
> 
> 
> I know this is quite a huge blob of data and you probably wont have the time to reconstruct it.
> I will just have to adjust my code that this can happen.
> BTW: Can you confirm that this is due to the use of IntView::lq ?
> I never experienced this without them.
> 
> Best,
> Max
> 
> 
> 
> 
> On 08/23/2012 12:40 PM, Guido Tack wrote:
>> 
>> I guess under certain conditions the code that posts the constraints (not the actual propagator) can be stronger than ICL_DEF, in which case this can happen.
>> If it's not too complicated, could you send us a concrete example?
>> 
>> Cheers,
>> Guido
>> 
>>   
> 
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