Talk:Pseudo-random Number Generator
> Seedable PRNG Based On MD5 Hashing > I haven't noticed any irregular behavior in this one, > i would love to know what you guys think - Kyrah Abattoir
Walking randomly by taking one built-in cryptohash after another sounds efficient and re-seedable and pseudo-random, aye.
On the down side, in this moment, my own knowledge of crypto maths isn't much deeper than Bruce Schneier's "Applied Cryptography", so I'd wonder about how solidly random the bits feel.
We could write code, to measure how random the bits feel, running inside or outside SecondLife, giving attention to particular bits not just the whole value.
I'd guess we'd thus show that cascading llMD5String feels more random than our instance of Linear Congruential, which in turn feels more random than our idiosyncratic Multiply Add Overflow.
-- Ppaatt Lynagh 07:41, 25 August 2012 (PDT)
rand can be optimized to and will be mono safe as...
integer rand(integer spread) {
seed2 = (seed2 * seed2Mod + 0xB);
return (seed1Mod = ((seed1 = (seed1 * (seed2Mod = seed1Mod) + 0xB)) * seed2)) % spread;
}
-- Strife Onizuka 11:25, 21 November 2007 (PST)
- I like to try to keep the code human-readable at first, but I'll add this as the optimized version. Thanks --Xaviar Czervik 09:55, 26 November 2007 (PST)
If we use 2 seeds, could we XOR "^" the seeds after modifiing the seeds, instead of "+" or "*"? to make it faster? —The preceding unsigned comment was added by Ollj Oh
- I haven't done cryptographic analysis of this function to ensure it's distribution but I'm inclined to say that you shouldn't use XOR. I think it would result in some quantity of bits being predictable. I'm pretty sure the distribution of this function is skewed regardless. If you feed it 1431655765, you should notice that numbers between -715827882 & 715827882 have twice the probability then those outside. With smaller numbers this type of skew is less noticeable, but as long as
((2147483648 % spread ) != 0)is true then you will have a skew. -- Strife Onizuka 09:07, 11 February 2008 (PST)