🚀 go-pugleaf

andrew@teslab.lab.OZ (Andrew Phillips  289 8712) writes:

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>Another interesting idea that I saw in sci.crypt recently is to test a PRNG
>by drawing pixels on a screen.  A good one will make something that looks
>like snow on a TV.  The eye can very easily detect some patterns which are
>caused by a poor PRNG. ...

A way to make this extremely sensitive for at least some schemes:
Method A:  Plot two sequential points as x and y on the screen.  But
only plot them if the first of the two is within a range which is very
narrow compared with the range of the generated numbers.  Obviously,
spread its axis so that narrow range fills the screen.

Method B:  Draw numbers till one falls in a narrow range, as in method 
A.  Draw two more, and plot them as X-Y.

Method A will display problems in congruential generators; method B is
nice to see how you have done on a binary shift register.  Expect to see
a pattern like a sawtooth wave for A and a pair of interleaved triangle
waves for B, on the suggested generator types...

>-- 
>Andrew Phillips (andrew@teslab.lab.oz{.au}) Ph. +61 (Aust) 2 (Sydney) 289 8712
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