srandomdev() vs srandom() vs arc4random()
Charles Swiger
cswiger at mac.com
Tue May 24 20:06:53 PDT 2005
On May 24, 2005, at 9:13 PM, Nicolas Blais wrote:
> I would like to know how "random" (that is, how inprobable a
> pattern will
> appear) if I use srandom(time(NULL)) instead of srandomdev().
> Also, would arc4random() be any better in getting the least pattern
> creation.
> Finally, is there is a way to check if the call srandomdev() exists
> on other
> OSes?
srandom() is an adequate RNG, but it tends to have poor distribution
of numbers (ie, specific bit patterns are more likely than others).
You might want to consider the Mersenne Twister RNG:
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
...which has appeared under both a GPL and a BSD-flavored license
over it's history.
--
-Chuck
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