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Re: [xquery-talk] [xsl] Re: Random number generation : requirements

2014-05-08 04:17:54
On 07/05/2014, Dimitre Novatchev dnovatchev(_at_)gmail(_dot_)com
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
On Tue, May 6, 2014 at 11:31 PM, Wolfgang Laun 
wolfgang(_dot_)laun(_at_)gmail(_dot_)com
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> 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
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