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Re: IDL random number generator [message #35038 is a reply to message #35027]

Fri, 09 May 2003 07:13

James Kuyper
Messages: 425
Registered: March 2000

Senior Member

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
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
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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