🚀 go-pugleaf

In article <C1H7tG.7At.2@cs.cmu.edu> tgl+@cs.cmu.edu (Tom Lane) writes:
>What I need is a very very fast random number generator; it does NOT need to
>be cryptographically strong.  The application is in generating random noise
>for dithering a color image.  I need about 8 random bits on each call
>(randomness of the low order bits is less important than the higher).
>Ideally it would take, say, just a shift and XOR per value.  The code has to
>be portable C, so circular shifts and other non-C operations are out.
>
>I think something along the lines of a shift register with a constant
>pattern XORed in after every shift might solve my problem.  But I don't
>know how to design such a thing.  Info or references would be appreciated.

If you don't need cryptographyically-strong, use the one in Numerical Recipes
in C, page 266 on the bottom.

Just be sure to clock the thing each time you take a bit.  If you need 8 bits,
clock it eight times after you take the 8 low-order bits.

Bruce