Messages in this thread | | | From | root@mauve ... | Subject | Re: Lockless file readingu | Date | Fri, 29 Aug 2003 00:44:00 +0100 (BST) |
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> > In article <200308281726.SAA24033@mauve.demon.co.uk> you wrote: > > I'd be really surprised if there were that many pictures in the world. > > Well, this is about probabilty. It does not mean that you need 2^64 > pictures, neighter does it mean you have a collision within 2^64 pictures.
Of course it dowesn't. The probability gets rather smaller as numbers go down, and bigger as they go up. With 2^128 bits, the chance of a a collision between 2^64 randomly chosen pictures is 50%. At 2^54 pictures, it's about one in a million, and at 2^34 (enough for several pictures of everyone alive) one in a billion billion. At more common numbers of pictures (say 2^14) it becomes vanishingly unlikely for anyone to have two matching pictures (even with several billion archives)
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