Re: A83: Help (Random)

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Re: A83: Help (Random)


On 22-May-98, John Kugelman wrote:

>Linus Akesson wrote:
>> 
>> First of all, deterministically speaking, there are NO random numbers. If I
>> asked you to give me a number, any number, then you are forced to come up
>with
>> a certain number, depending on what electrons are where in your brains.
This
>> also means that computers cannot produce random numbers either. However
>> cryptic an algorithm you use to convert a seed number (f.ex. a timer) into
a
>> pseudo-random number, there will always be a mathematical formula (that
>> probably can be simplified too).

>Of course quantum physics says that nothing can be predicted completely
>accurately since particle motion is random.

Define random. Besides, I never said anything about predicting anything...

>> What I am trying to say is that there's no use in writing complex
>> random-number-generating routines, as the numbers they generate wouldn't be
>> _really_ random anyway. Actually, adding 1 to the last "random" number is
>> often sufficient! But then the user would spot the algorithm too easy. I'd
>> recommend rotating the previous "random" number with some constant, and
then
>> adding another constant. For an 8 bit number:
>> 
>> random:      ld   a,(prevrand)
>>              rla
>>              rla
>>              rla
>>              add  a,31h
>>              ld   (prevrand),a
>>              ret
>> 
>> Want a 16-bit number? Call the function twice!

>Just because truly random numbers can't be generated doesn't mean you
>can't try.  I would hate to see you write a gambling program, or perhaps
>some kind of Monte Carlo simulation.  The randomness of a particular
>generator can in fact be determined by many factors, including its
>period, or the time it takes to repeat itself.  I would expect this type
>of algorithm to have a very short period, probably less than 1000.  The
>numbers won't be very "random" either.

Yeah, you're probably right. But in most situations it really IS enough just
to add 1 to the previous random number.

>Here's a web site on one of the newest and best random number
>generators, and its quite speedy, too.

>http://www.math.keio.ac.jp/~matumoto/emt.html

Regards, I'll check it.

>-- 
>John Kugelman.  kugelman@mnsinc.com

>I believe we can change anything.
>I believe in my dream.
>    - Joe Satriani

Linus.
I believe we can't change anything. (Just changed your quote =).)
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