[fpc-pascal] GUIDs under FreeBSD don't seem very random

Graeme Geldenhuys mailinglists at geldenhuys.co.uk
Wed Jan 6 01:14:01 CET 2016


On 2016-01-05 23:56, Graeme Geldenhuys wrote:
> From Wikipedia (GUID vs UUID)
> -----------------------------
> The term GUID usually refers to Microsoft's implementation of the
> Universally Unique Identifier (UUID) standard.

Reading further on Wikipedia I now understand you get different versions
of UUID's. My first set of values were Version 1 (MAC address &
date-time) type, and the second set was a Version 4 (Random) set.

That explains why they looked so different.


> So am I to assume that I will still get unique values even if I generate
> 1-2 million records in succession?

>From the Wikipedia explanation on how Version 1 UUID's are generated I
think it is safe to assume that generating 1-2 million UUID's (aka
GUID's) is succession should be fine and the likelihood of duplicates
are still extremely small.


Probability of duplicates (also from Wikipedia)
------------------------------------------------
...snip...
To put these numbers into perspective, the annual risk of a given person
being hit by a meteorite is estimated to be one chance in 17 billion,
which means the probability is about 0.00000000006 (6 × 10−11),
equivalent to the odds of creating a few tens of trillions of UUIDs in a
year and having one duplicate.


That's odds I'll accept for now. ;-)


[Sorry for the mailing list noise. It seems with my own research (after
my initial post) I now managed to answered my own question.]

Regards,
  - Graeme -

-- 
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
http://fpgui.sourceforge.net/

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