NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/programmer/4484

Internet Message Format | 1996-08-05 | 3.4 KB

Path: informatik.tu-muenchen.de!fischerj
From: [e-mail] (Juergen "Rally" Fischer)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Random Number Generation
Date: 29 Feb 1996 13:12:12 GMT
Organization: Technische Universitaet Muenchen, Germany
Distribution: world
Message-ID: <4h48nc$[e-mail]>
References: <[e-mail]> <[e-mail]>   <[e-mail]> <[e-mail]>  <[e-mail]> <4g2bi9$[e-mail]> <[e-mail]> <[e-mail]>
NNTP-Posting-Host: hphalle2i.informatik.tu-muenchen.de
Originator: [e-mail]


In article <[e-mail]>, [e-mail] (Wessel Dankers) writes:
|> >> #include <stdlib.h>
|> >> ....
|> >>    num = ( (float) rand() / 32767E0 ) * ( high - low ) + low;
|>
|> >In theory, this is a very good suggestion.  In practice, rand() is a
|> >very poor RNG.  Run any common statistical tests on rand()'s output
|> >to see.
|>
|> What's wrong with FastRand()?
|>
|> From a totally unexpected corner I got this article, which, amongst a lot of
|> stuff about why god doesn't exist, contained the following algorithm as an
|> *example*, so I don't know how good it is. (layout slightly changed by me).

AFAIK very good. I have tested such a "shift and eor" years ago, and
it was good enough to generate .... what's the word for the thing a
TV does if there's no channel ? :)
Well, the function does it both for gfx and sound.

float. naaaaah.

|>
|> --
|> From: PAGAN <[e-mail]>
|> Subject: Re: Atheism; the perfect antidote to poetry and style.
|> Date: Sat, 10 Feb 96 04:15:01
|> Newsgroups: alt.atheism.moderated
|>
|> /*********************************************************************
|>  RANDOM number generator
|>      returns a random number from one to the value passed
|>      repeat rate OTO 1e6
|> *********************************************************************/
|> int random(int val)
|> { int num;                        /* this is what will be returned */
|>   int bit0, bit1, bit14;
|>   static int rndval=2;            /* seed value */
|>
|>   if(val<0)                       /* if a negative value passed */
|>       rndval=-val;                /* reseed */
|>
|>   bit0 = rndval & 1;
|>   bit1 = (rndval & 2) >> 1;
|>   bit14 = bit0 ^ bit1;
|>   rndval >>= 1;
|>   rndval  |= bit14 << 14;
|>
|>   num = rndval % val;

huh ? a div ? I sugesst to get it run without div.

|>   return num ? num : val;
|> }
|>
|> /*********************************************************************
|>  SEED the RANDOM number generator
|>      random number seed for the above
|> *********************************************************************/
|> seedrandom()               /* negative value to seed the generator */
|> { random(-systemticks());  /* seed with system tick count */
|> }
|> --
|>
|>
|> --
|> Wessel Dankers                 _\\|//_            <[e-mail]>
|>                                ///|\\\
|> ----------------------------oOO--(_)---OOo----------------------------
|> `Never imagine yourself not to be otherwise than what it might appear
|> to others that what you were or might have been was not otherwise than
|> what you had been would have appeared to them to be otherwise.'
|>