[PD-dev] RNG

[Miller Puckette]

Hi Krzysztof,

I've never carefully tested the RNG in Pd, just typed out two huge
numbers with my eyes closed, and never read that part of Knuth...
If there's a good, simple cross-platform random number generator I'd be
happy to use it, but I wouldn't trust anything native to Windows.
Finally I could find no better solution than to write my own, bad
one.  I did listen to noise~ output (sounded OK), looked at its spectrum
(looks mighty flat) and did a histogram on a "random 10" (got 10 roughly
equal numbers).

I think I did the same thing in the original Max but by now it might be
replaced with something better, I dunno...

cheers
Miller


On Tue, Aug 27, 2002 at 04:33:11PM +0200, Krzysztof Czaja wrote:
> hi Miller and others,
> 
> as I have resumed cyclone hacking today (after a long break),
> I would like to finish coding the 'random' family first.
> 
> Not being even close to an expert on random number generators,
> I have borrowed the two used in the 'random' and 'noise~'
> builtins.  Today, just in order to have a quick try, I have used
> them to produce an input for the 'diehard' set of tests.  Now
> I have three questions:
> 
> 1. Before I start learning how to correctly interpret all the
> results -- have been such, or similar, or any kind of tests,
> performed for the Pd rngs?
> 
> 2. Seeing that the one used in noise~ (d_osc.c) has suboptimal
> period length (2^{30}), I wonder if this does matter for the
> `whiteness' of the output, or does not?  (The multiplier
> a = 435898247 fails the property of b = a - 1 being a multiple
> of 4 -- this is in Knuth 3.2.1.2, at least in a Polish
> translation:)
> 
> 3. Waiting for a return of our mac used for checking things in
> max/msp, I am not able yet to check what kind of output max/msp
> rng produces.  Any hint?
> 
> thanks,
> Krzysztof
> 
> 
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