From: Kish Shen <kisshen_at_cisco.com>

Date: Wed, 14 Mar 2012 18:23:31 +0000

Date: Wed, 14 Mar 2012 18:23:31 +0000

Hi Sergey (and others), Several comments: ic does not handle large integers, i.e. it does not use the bignum representation of integers that ECLiPSe supports (implemented with GNU's GMP). I don't think any integer finite domain solver will handle a large finite domain well, both because reasoning and propagating over large domains is expensive (e.g. many constraints have a very heavy dependency on the domain size(s) of its variabes (particularly if they are domain consistent); and also labelling variables with large domain is expensive (unless propagation is able to very significantly reduce the domain size). In the case of ic, where a finite domain is represented as a bitmap (1 bit per domain value) as soon as a hole appears in the domain, this is particularly inefficient if you have a large domain. Sergrey, you used labeling/1 in the code you showed, but I assume you must have given a finite integer interval to the variables, because you get an error when you try to label IC variables that do not have a finite integer range. The running of the example with lib(fd) is not "correct" in the sense that fd correctly handles large integers in the constraint, as fd variables are given a default range (-10,000,000 to 10,000,000), and the constraint limits the range of integer range for A,B,C,D accordingly, and it is only these values that will be tried. If you try to give a variable in a constraint a value that will result in a value that is outside this default range, the constraint will fail, e.g.: :- lib(fd). :- A*A #= B*B + C*C, A = 50000. fails. [this is incorrect in the sense that with large enough range, the above does have a solution] Thorsten: I think gfd is much slower in this example because for the constraint A*A*A*A + B*B*B*B +C*C*C*C #= D*D*D*D does not seem to take into account the default interval given to the variable, and seem to be reasoning assuming the variables have the full (32 bit) range (it assigns a domain of 1..46340 to the variables after posting of this constraint, compared to 1..3162 for lib(fd)). [lib(gfd) does give a default interval (currently -1,000,000..1,000,000) to variables whose domain are not explicitly specified] Cheers, Kish On 14/03/2012 07:33, Matteo Bellotto wrote: > Dear Sergey, > the way numbers are managed depend on the particular solver used. > In your email there's a generic reference to ECLiPSe and this isn't sufficient. The only clue you gave is the use of integer constraints. So I supposed you're talking about the "IC" solver. > > In this case you could read the documentation below: > > http://eclipseclp.org/doc/libman/libman017.html > > and > > http://eclipseclp.org/doc/libman/libman019.html > > In general, despite the particular solver you are referring to, I think that RTFM it's a good starting point. > > Have a nice reading, > Matteo. > > > ________________________________ > Da: Sergey Dymchenko<kit1980_at_gmail.com> > A: Matteo Bellotto<matteob8_at_yahoo.it> > Cc: "eclipse-clp-users_at_lists.sf.net"<eclipse-clp-users_at_lists.sf.net> > Inviato: Marted́ 13 Marzo 2012 14:03 > Oggetto: Re: [eclipse-clp-users] Large integers and delayed goals > > Hi Matteo, > > My question was more about how ECLiPSe works with large integers, not > about this particular problem. > And it's clear that if we constrain our variables to be at most 100 we > will not get rounding errors. > > Sergey. > > On Tue, Mar 13, 2012 at 2:31 PM, Matteo Bellotto<matteob8_at_yahoo.it> wrote: >> Hi Sergey, >> using your code I obtained the same, wrong, result. >> I've sligtly modified your code, defining explicitly the domain of the >> variables, and this update has improved the search, i.e. I didn't get any >> "wrong answer". >> Here there the modified code: >> >> :-lib(ic). >> test(Result):- >> Result=[A,B,C,D], >> Result:: 1..100, >> >> A #> 0, B #> 0, C #> 0, D #> 0, >> A #=< B, B #=< C, C #=< D, >> A*A*A*A + B*B*B*B + C*C*C*C #= D*D*D*D, >> labeling([A, B, C, D]). >> >> ?- test(R). >> No (22.43s cpu) >> >> Please note that, increasing the domains bounds, the search will take a >> (really) longer time. >> >> Bye, >> Matteo. >> >> Da: Sergey Dymchenko<kit1980_at_gmail.com> >> A: eclipse-clp-users_at_lists.sourceforge.net >> Inviato: Venerd́ 9 Marzo 2012 18:24 >> Oggetto: [eclipse-clp-users] Large integers and delayed goals >> >> Hi, >> >> I want to find positive natural numbers A, B, C, D, such that A^4 + >> B^4 + C^4 = D^4. >> My program do this: >> >> A #> 0, B #> 0, C #> 0, D #> 0, >> A #=< B, B #=< C, C #=< D, >> A*A*A*A + B*B*B*B + C*C*C*C #= D*D*D*D, >> labeling([A, B, C, D]) >> >> But I get incorrect result [1, 1, 9742, 9742] with 10 delayed goals. >> As far as I understand, the system finds that the result is imprecise, >> but correct enough because 9742^4 is a large number. >> Probably floating arithmetic is used, not big integers... >> Is there a way to force precise arithmetic for large integers? >> >> Sergey. >> >> ------------------------------------------------------------------------------ >> Virtualization& Cloud Management Using Capacity Planning >> Cloud computing makes use of virtualization - but cloud computing >> also focuses on allowing computing to be delivered as a service. >> http://www.accelacomm.com/jaw/sfnl/114/51521223/ >> _______________________________________________ >> ECLiPSe-CLP-Users mailing list >> ECLiPSe-CLP-Users_at_lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/eclipse-clp-users >> >> >> >> ------------------------------------------------------------------------------ >> Keep Your Developer Skills Current with LearnDevNow! >> The most comprehensive online learning library for Microsoft developers >> is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, >> Metro Style Apps, more. Free future releases when you subscribe now! >> http://p.sf.net/sfu/learndevnow-d2d >> _______________________________________________ >> ECLiPSe-CLP-Users mailing list >> ECLiPSe-CLP-Users_at_lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/eclipse-clp-users >> > > ------------------------------------------------------------------------------ > Virtualization& Cloud Management Using Capacity Planning > Cloud computing makes use of virtualization - but cloud computing > also focuses on allowing computing to be delivered as a service. > http://www.accelacomm.com/jaw/sfnl/114/51521223/ > _______________________________________________ > ECLiPSe-CLP-Users mailing list > ECLiPSe-CLP-Users_at_lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/eclipse-clp-users -- This e-mail may contain confidential and privileged material for the sole use of the intended recipient. 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