[gecode-users] Propagating to Fixpoint
Max Ostrowski
ostrowsk at cs.uni-potsdam.de
Fri Aug 24 09:57:02 CEST 2012
I was not modeling but writing a propagator.
Thanks for solving my problem.
Best,
Max
On 08/24/2012 09:54 AM, Christian Schulte wrote:
>
> There are in fact several big fat warnings in MPG saying that views
> are not for modeling! They are there for a reason!
>
>
>
> Christian
>
>
>
> --
>
> Christian Schulte, www.ict.kth.se/~cschulte/
>
>
>
> *From:* users-bounces at gecode.org [mailto:users-bounces at gecode.org] *On
> Behalf Of *Max Ostrowski
> *Sent:* Thursday, August 23, 2012 2:05 PM
> *To:* Guido Tack
> *Cc:* users at gecode.org
> *Subject:* Re: [gecode-users] Propagating to Fixpoint
>
>
>
> Great, this really solves the problem.
> Have not thought of this.
> Thank you very very much.
> In my example everything works as expected and the fixpoint is always
> the same.
> Are you sure that it can still happen that the fixpoint of the same
> set of constraints is different,
> if i use a different order?
> Then i have to stick to my fallback method.
>
>
> Nevertheless,
> big thanks for solving my problem. Everything works now and is a
> hundred times faster :)
>
> Best,
> Max
>
> On 08/23/2012 01:44 PM, Guido Tack wrote:
>
> 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
> <mailto: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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