[Qt-interest] QUuid with QUuid::Time

[Oliver.Knoll at comit.ch]

Constantin Makshin wrote on Monday, June 14, 2010 9:50 PM:

> IMHO, even 7 duplicates per 15 million values (~0.00005% chance of
> collision) is [more than] acceptable result for most, if not all,
> applications. :)

But can we agree upon the following: 

Given propability p1 of a "UUID collision", as suggested to be "infinitely small" by descriptions such as:

  "For example, consider the observable universe, which contains about 5×10^22 stars; every star could then have 6.8×10^15 universally unique GUIDs."

and given probability p2 = ~0.00005% of a real world UUID generator implementation, that there are, well, "light years" (as to stay in the figurative speech of the http://en.wikipedia.org/wiki/Globally_Unique_Identifier article) between p1 and p2?
  
> I agree with one of the posters from that discussion:
> "chances are so low that you really should stress about something
> else- [...]"

I also generally agree on that :) It is always a question of "how bad" the impact of a duplicate really is and whether it is worth bothering. But for example if - and I stress the IF here - you'd rely on a UUID for identifying finanical transactions it could turn out disastrous... Or would you trust a bank which would officially state that "our online banking/transactions are (technically) 0.99995% safe"? ;)

Cheers, Oliver
-- 
Oliver Knoll
Dipl. Informatik-Ing. ETH
COMIT AG - ++41 79 520 95 22