(n-1)+x(n-2),but taken modulo 2^32.
   Its period is 3*2^31 if one of its two seeds is odd
   and not 1 mod 8. It has little worth as a RNG by
   itself, but provides a simple and fast component for
   use in combination generators.
</i></p><p>
<i>   SHR3 is a 3-shift-register generator with period
   2^32-1. It uses y(n)=y(n-1)(I+L^17)(I+R^13)(I+L^5),
   with the y's viewed as binary vectors, L the 32x32
   binary matrix that shifts a vector left 1, and R its
   transpose. SHR3 seems to pass all except tho