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    SubjectRe: Lockless file readingu
    On Fri, Aug 29, 2003 at 12:44:00AM +0100, wrote:

    > 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)

    Be careful. I remember discussing in probability class the liklyhood that
    two people in a room with N people have the same birthday. N does not have
    to be anywhere close to 365 for your probability of a collision to be greater
    than 50%. I forget what the exact number is but its less than 30. The
    image problem sounds similar, depending on exactly how you phrase it.


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