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Re: [xquery-talk] Re: Random number generation : requ

Subject: Re: [xquery-talk] Re: Random number generation : requirements
From: "Wolfgang Laun wolfgang.laun@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 8 May 2014 09:17:42 -0000
Re: [xquery-talk]  Re: Random number generation :  requ
On 07/05/2014, Dimitre Novatchev dnovatchev@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, May 6, 2014 at 11:31 PM, Wolfgang Laun wolfgang.laun@xxxxxxxxx
> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>> For instance: In Dimitre's example: values returned alternate between
>> even and odd,
>
>
> Not true:
>
> From the 2002 article:
>
> 100 Randoms in (1, 10): 3, 10, 2, 9, 7, 2, 3, 10, 9, 4, 4, 3, 1, 5, 4,
> 10, 3, 6, 7, 1, 1, 10, 8, 3, 9, 3, 4, 1, 1, 5, 8, 6, 2, 5, 10, 1, 3,
> 8, 8, 10, 5, 1, 9, 10, 3, 10, 3, 2, 2, 8, 3, 8, 3, 8, 5, 2, 7, 6, 7,
> 2, 8, 1, 9, 8, 2, 4, 5, 2, 10, 8, 9, 9, 3, 10, 9, 6, 5, 8, 7, 3, 3, 3,
> 5, 3, 5, 9, 9, 10, 5, 2, 5, 1, 5, 1, 6, 8, 3, 6, 4, 1,

But it *is* true. Any formula of the pattern

   rand*multiplier + increment

exhibits this property:

   odd*odd + odd -> even
   even*odd + odd -> odd

But: The higher the bits you take out of the basically generated
random number (as you obtain them by dividing by some range) the more
"random" they are.

>
> Also, there is absolutely no obstacle in using as many random
> generators (sequences) as needed -- one just needs a different seed
> for each of them.
>
> Please, read the article carefully.

I didn't say anything about your implementation. I just wanted to
state that the planned function should have this feature. - Please
don't read anything I haven't written ;-)

-W

>
>
> --
> Cheers,
> Dimitre Novatchev
> ---------------------------------------
> Truly great madness cannot be achieved without significant intelligence.
> ---------------------------------------
> To invent, you need a good imagination and a pile of junk
> -------------------------------------
> Never fight an inanimate object
> -------------------------------------
> To avoid situations in which you might make mistakes may be the
> biggest mistake of all
> ------------------------------------
> Quality means doing it right when no one is looking.
> -------------------------------------
> You've achieved success in your field when you don't know whether what
> you're doing is work or play
> -------------------------------------
> To achieve the impossible dream, try going to sleep.
> -------------------------------------
> Facts do not cease to exist because they are ignored.
> -------------------------------------
> Typing monkeys will write all Shakespeare's works in 200yrs.Will they
> write all patents, too? :)
> -------------------------------------
> I finally figured out the only reason to be alive is to enjoy it.

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