[PD] help_random/seed

Mike Moser-Booth mmoserbooth at gmail.com
Sun Jul 5 05:24:27 CEST 2009

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.

> mfgasdr
> IOhannes
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