# [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

.mmb
>
>
> mfgasdr
> IOhannes
>
>
>
>
>
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```