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Re: IDL random number generator [message #35027 is a reply to message #35026]

Sat, 10 May 2003 15:17

tandp
Messages: 8
Registered: November 2000

Junior Member

In article <3EBBB786.9C52F5F3@saicmodis.com>, James Kuyper
<kuyper@saicmodis.com> wrote:

> krijger@astro.uu.nl wrote:
>>
>> Hi,
>> I know that randomn is pseudo-random, how many numbers can you
>> generate before the non-randomness kicks in?
>>
>> Thijs Krijger
>
> None. The non-randomness is there from the very beginning. You could
> make a true random number generator by running it off of the radioactive
> decay of atoms, or some similar hardware-based approach. However,
> software random number generators are absolutely deterministic, once
> you've set up the seed. You can set the seed form a clock setting, which
> means that the precise sequence of random numbers generated depends upon
> the precise time at which the program reads the clock. But even the very
^
| and the seed

> first number can be absolutely predicted from the seed value.
>
> Every random number generator has a period, after which it starts
> repeating the same exact sequence. How long that period is depends upon
> the quality of the algorithm used. Commonly used algorithms have periods
> in the range of 100,000 numbers or better. Very sophisticated generators

The best pseudorandom number generator (congruence method and seed chosen
to be the largest prime ineteger representable in a word) will have a
period equal to the seed value.

> can have periods that are so long that your computer will become
> obsolete before the sequence repeats.

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[Message index]

		Re: IDL random number generator By: James Kuyper on Mon, 12 May 2003 08:15
		Re: IDL random number generator By: krijger on Mon, 12 May 2003 02:29
		Re: IDL random number generator By: James Kuyper on Sat, 10 May 2003 23:30
		Re: IDL random number generator By: tandp on Sat, 10 May 2003 15:17
		Re: IDL random number generator By: James Kuyper on Fri, 09 May 2003 07:13
		Re: IDL random number generator By: tandp on Mon, 12 May 2003 10:12
		Re: IDL random number generator By: Matt Feinstein on Mon, 12 May 2003 11:06

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