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MathGroup Archive 2004

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Re: random numbers?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46122] Re: [mg46110] random numbers?
  • From: "Sseziwa Mukasa,,(978) 536-2359" <mukasa at jeol.com>
  • Date: Sat, 7 Feb 2004 04:02:03 -0500 (EST)
  • References: <200402060915.EAA19284@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On Feb 6, 2004, at 4:15 AM, sean kim wrote:

> hello group.
>
> this is gonna sound silly.
>
> How do ppl make random number generators?   is a random number
> generator like a routine that picks a given set of different number
> then goes back to the beginning and starts over?

There are a variety of ways, Chapter 7 of Numerical Recipes describes 
some of the most common methods, it's available online at 
http://www.library.cornell.edu/nr/bookcpdf/c7-0.pdf.

I believe Mathematica uses a sequence based on the evolution of a 
cellular automaton, at least in some cases.  Further description can be 
found on page 317 of A New Kind of Science which is available here 
http://wolframscience.com/nksonline/page-317?firstview=1.

> How does mathematica determine if a numbder is random?  or is that
> even a right question to ask?

Randomness is a property of a sequence not an individual number.  There 
are a variety of tests of increasing sophistication used to test a 
sequence for randomness, a quick Google search will provide you with 
more than enough starting points for further research.

> I just wanted to know what the random generator is.

There isn't a single one.

>  and how it's used
> in Mathematica.

The link to A New Kind of Science will tell you how the expression 
Random[Integer] is evaluated, at least in the case of large integers.  
If you are really curious perhaps you should ask Wolfram Technical 
Support.

Regards,

Ssezi


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