From: Stefan.Lucks@uni-weimar.de
Subject: Re: Lotto simulation
Date: Mon, 16 Jun 2014 07:25:10 +0200
Date: 2014-06-16T07:25:10+02:00 [thread overview]
Message-ID: <alpine.DEB.2.10.1406160715490.4637@debian> (raw)
In-Reply-To: <lnktj7$gp$1@dont-email.me>
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On Sun, 15 Jun 2014, J-P. Rosen wrote:
> Le 15/06/2014 20:54, Stefan.Lucks@uni-weimar.de a écrit :
>> The alternative is to (2n) instantiate a single random generator (I've
>> forgotten the package name, but it is not A.N.Discrete_Random), which
>> just generates a Float F_Rand between 0 and 1. Then set R_I :=
>> Truncate(1 + F_Rand * (50-I)).
> This is not equivalent. I don't remember the details, but in the making
> of Ada 95 there was a furious discussion between numericists about
> whether it was possible to make a discrete random generator given a
> floating point random generator.
>
> After megabytes of E-mail discussion, they concluded that NO, it was not
> possible, and therefore that Ada should have both.
I am not aware of that discussion, but mathematically, given a uniformly
distributed real number F between 0.0 and 1.0, one can get a uniformly
distributed discrete D between Low and high: D := Truncate(Low + F *
(High-Low + 1)).
I guess, the issue that has been raised in that discussion that if F is of
type float or even double-float, it has a mantissa of limited size, and
then the distribution of D would significantly deviate from the uniform
distribution if High-Low happens to be large. In the current case,
however, High-Low < 50, so the solution using the uniformly distributed
float should work properly. If D would significantly deviate from the
uniform distribution, then so would F.
------ I love the taste of Cryptanalysis in the morning! ------
<http://www.uni-weimar.de/cms/medien/mediensicherheit/home.html>
--Stefan.Lucks (at) uni-weimar.de, Bauhaus-Universität Weimar, Germany--
next prev parent reply other threads:[~2014-06-16 5:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-15 17:07 Lotto simulation montgrimpulo
2014-06-15 18:54 ` Stefan.Lucks
2014-06-15 19:53 ` J-P. Rosen
2014-06-16 5:25 ` Stefan.Lucks [this message]
2014-06-16 7:49 ` J-P. Rosen
2014-06-16 11:15 ` Stefan.Lucks
2014-06-16 13:40 ` J-P. Rosen
2014-06-16 14:13 ` Natasha Kerensikova
2014-06-16 17:51 ` Randy Brukardt
2014-06-15 19:56 ` Denis McMahon
2014-06-15 20:10 ` Dirk Heinrichs
2014-06-15 20:43 ` Simon Wright
2014-06-16 20:22 ` Dirk Heinrichs
2014-06-15 20:54 ` Simon Wright
2014-06-15 22:09 ` Jeffrey Carter
2014-06-16 11:40 ` Markus Schöpflin
2014-06-16 14:25 ` Jacob Sparre Andersen
2014-06-16 12:02 ` Dmitry A. Kazakov
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