Bit-twiddling

[Ivan Frohne]

> Based on this advice I took a stab at the rest of the algorithm and
> now it actually works! Wheee! So if anyone wants a string of random
> numbers with a period of 2**199937-1 and equi-distributed in 623
> dimensions, just let me know. :-)
>
> | if-you're-really-after-random-numbers-see-ivan-frohne-ly y'rs  - tim

I have a new version of the Mersenne Twister just around the corner
that uses the Numeric module if it's available.  This makes it almost
as fast as whrandom.

To get a right shift for ordinary integers that always shifts in high-order
zeros, this
works (x is an ordinary 32-bit signed integer):

 x >> 1 & 0x7FFFFFFF  #  Logical right shift 1
 x >> 2 & 0x3FFFFFFF  #  Logical right shift 2
.....
 x >> 11 & 0x001FFFFF  # Logical right shift 11

etc.

--Ivan Frohne