[vcf-midatlantic] Random numbers

Dave McGuire mcguire at neurotica.com
Sat Apr 8 13:06:21 EDT 2017

On 04/08/2017 12:10 PM, Dan Roganti via vcf-midatlantic wrote:
>> ​Remember,
>> that step to seed the rnd generator is not perfect either​
>>>> ​, eg. RND(-32768) or whichever value​
>> ​if you use the same seed, guess what,
>> you get the same random numbers :)
> ​This is why you like to use something "random" to seed the rnd generator​
> Usually every computer has a free running counter,
> meaning it's constantly being updated in the background

   If some of my dustiest neurons are working, in the Atari at least 
there's a scan line counter from the video subsystem available for 
reading.  At least I think it was something like that.  That was great 
for seeding random number generators.  The Apple ][ must have something 
like that.

   Random number generation itself is a fascinating topic and a very 
difficult nut to crack.  There are multiple large books published about 
it.  There are financial-industry-quality high-speed hardware random 
number generators on the market, used for generating crypto keys.  Some 
are quite elaborate, using very fancy algorithms to de-bias the number 
stream.  Some use reverse-biased P-N junctions as their initial source, 
and some even use tiny bits of radioactive materials coupled to 
scintillation crystals and photodiodes.  It's a fascinating field. 
Generating true randomness is actually very, very hard.


Dave McGuire, AK4HZ
New Kensington, PA

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