PRNG proposal

[Matthew Woehlke]

Ok, after fiddling more with integer-only algorithms, here's something 
that isn't *too* horribly many operations, that's non-recursive and only 
uses only integers. It seems to look okay*, but hasn't been tested for 
any sort of distribution theory.

quint64 myRand48(quint64 n, quint64 a, quint64 b)
{
     return ((n * a) + b); // needed?? & 0xFFFFFFFFFFFF;
}

quint64 myRandom(int x, int y, int seed)
{
     quint64 n = (quint64(x) * 1103515249) + (quint64(y) * 91573268041) 
+ seed;
     n = myRand48(n, 8759824322359, 13);
     n = (n >> 24) ^ (n << 24);
     n = myRand48(n, 200560490131, 2707);
     n ^= x ^ (y * 39916801);
     return myRand48(n, 26329792769470687, 62017);
}

(* the lower several bits are still obviously patterned. As long as the 
upper ~40 bits are favored this should be ok, but taking the result 
&0xFF won't work well.)

I won't feel hurt if y'all don't like this. I'd be *thrilled* if anyone 
can improve it :-). It's just something that /might/ (and I do stress 
"might") be usable as a pure-integer algorithm.

(In its favor - though I think this is true of the current algorithm 
also - it achieves one of my goals, which is that changing the seed 
completely changes the output.)

-- 
Matthew
Please do not quote my e-mail address unobfuscated in message bodies.
-- 
|-\ /-\ \ | -+-   |-\  +  \ | -+- /-\
| | | | |\|  |    |-/ /-\ |\|  |  |
|-/ \-/ | \  |    |   | | | \ -+- \-/