🚀 go-pugleaf

>In article <36984@sdcc12.ucsd.edu>, whart@cs.ucsd.edu (Bill Hart) writes:
>|> I have an application for which I need to generate a random 'vector' of 
>|> bits of length N.  
>
>nmm@cl.cam.ac.uk (Nick Maclaren) writes:
>Standard warnings:
>
>    2) Don't trust Numerical Recipes - about half of its techniques are
>reliable, but the others contain serious traps.  

	I agree.

>Perhaps the best method for your application is a Tausworthe (also called
>shift-register, primitive polynomial over GF(2), etc.) with a generating
>polynomial of order at least N.

	Indeed, although one cannot generalize the properties of 
	shift-register generators, especially many GFSR (generalized feedback
	shift-register) generators have been noticed to have good 
	statistical bit-wise properties. The results, however, depend 
	strongly on initialization and the choice of exponents in the 
	primitive polynomial (like p and q in a polynomial 
	x**p + x**q + 1 ). Hence it might be a quite good choice to 
	call such a generator with integers, and transform them to 
	bits. These words of bits you could use for your purpose. Notice, 
	however, that this rng should not be called to get real numbers 
	distributed [0,1) and then multiplied with some integer (like 
	2**p - 1, where p is the number of bits in a particular cpu). 
	This way you will get only 24 random bits out of 31 (on a 
	32-bit machine), due to 24-bit mantissas in real mode...

>I am afraid that there is no simple solution to the general case of random
>vectors of bits, but there are several fairly reliable ones.

	And one quite reliable method is to take only few most 
	significant bits out of random numbers. Usually all the bits 
	are not random, but at least 10 of the most significant ones 
	are. But - do not use RAN3 (in Numerical Recipes ), if you 
	want random bit-wise properties... This is due to my own 
	experiences :-/

	vattu@ee.tut.fi