Re: [eclipse-clp-users] Large integers and delayed goals

From: Sergey Dymchenko <kit1980_at_gmail.com>
Date: Tue, 13 Mar 2012 15:03:58 +0200
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.
>
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Received on Tue Mar 13 2012 - 13:04:08 CET

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