Ron Parker <ron### [at] povrayorg> wrote:
: next_rand[stream] = next_rand[stream] * 1812433253L + 12345L;

: which doesn't look particularly well-chosen to me.

  It depends on what you want to do, but basically you are right, it's not
excellent.
  There are better methods which give more randomness and much large periods.
  For example the C library function (not standard but found in most unix
compilers and perhaps others as well) for random() is described in the
following way:

     The random() function uses  a  nonlinear  additive  feedback
     random-number generator employing a default state array size
     of 31  long  integers  to  return  successive  pseudo-random
     numbers  in  the range from 0 to 2**31-1. The period of this
     random-number generator is approximately 16 x (2**31-1). The
     size  of  the  state  array  determines  the  period  of the
     random-number generator. Increasing  the  state  array  size
     increases the period.

  If I understand this correctly, it uses a whole array as seed value instead
of one integer. I suppose that this way more randomness is achieved and
a much larger period (16*(2^31-1) is pretty large).

-- 
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););}    /*- Warp -*/

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