[PD] help_random/seed

[Ian Andrews]

Just an ignorant assumption, but would not the output of [noise~]  
itself be generated from pseudo-random numbers? If not, then how does  
[noise~] generate its randomness? Or is there something more complex  
at work?

Ian

On 05/07/2009, at 7:12 PM, Andrew Faraday wrote:

>
> Just an idea, but if the hardware random number generators use a  
> jittery oscillator etc. Why not use [noise~] and [snapshot~]  
> followed by some arithmetic and [int] you could build what I assume  
> would be more random than the [random] box.
>
> Andrew
>
> > Date: Sun, 5 Jul 2009 00:22:51 -0400
> > From: martin.peach at sympatico.ca
> > To: mmoserbooth at gmail.com
> > CC: pd-list at iem.at; zmoelnig at iem.at
> > Subject: Re: [PD] help_random/seed
> >
> > Mike Moser-Booth wrote:
> > > IOhannes m zmölnig wrote:
> > >> Frank Barknecht wrote:
> > >>> Hallo,
> > >>> cem guney hat gesagt: // cem guney wrote:
> > >>>
> > >>>> just started studying PD. going through the control examples  
> i've
> > >>>> been stuck trying to figure out the function of the message,  
> seed
> > >>>> 123 in the
> > >>>> example for "random". not sure if i figured out the  
> explanation below,
> > >>>>
> > >>>> Seeds are kept locally so that if two Randoms are seeded the  
> same
> > >>>> they will have the same output (or indeed you can seed the  
> same one
> > >>>> twice to repeat the output.)
> > >>>
> > >>> Yes, that's true, you understood correctly.
> > >>>
> > >>> Oh, wait, that's what's in the help-file! What exactly is  
> cloudy there?
> > >>
> > >> probably the simple fact, that [random] despite of it's name  
> does not
> > >> really produce random numbers.
> > >> mostly when computers present you a "random" number, then this  
> number
> > >> will only appear to be random, but in reality is just  
> calculated as
> > >> the next item of a totally deterministic series.
> > >> (as a matter of fact, a new random number is usually generated by
> > >> simple taking the last number and then applying some more or less
> > >> complicated transformation on this number). this method is  
> known as
> > >> "pseudo random".
> > >>
> > >> you can set the "starting point" of the series by setting the  
> "seed",
> > >> which is the first number of the random sequence). since all  
> [random]
> > >> object use the same algorithm to calculate the next pseudo-random
> > >> number, they will all end up with the same sequence if they all  
> start
> > >> with the same "seed".
> > >> by default Pd uses different seeds for all [random] objects so  
> they
> > >> all appear to work independently.
> > > In addition, it's probably worth mentioning that Pd will produce  
> the
> > > same seeds for each [random] every time you load the patch. So  
> while
> > > they appear to work independently, you will still get the same  
> results
> > > each time you first run a patch after loading it.
> > >
> >
> > A lot of the latest cpus have hardware random number generators that
> > work by having a jittery oscillator sample the cpu clock, or  
> something
> > along those lines. (Such a jittery oscillator is assumed to have
> > normally distributed transition times.)
> > It would be nice if the random source could be independently  
> specified
> > for all the pd objects that use random numbers, since the count of
> > unreachable combinations when using the standard deterministic chaos
> > generators is infinite.
> >
> > Martin
> >
> >
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