On Wednesday April 11, [EMAIL PROTECTED] wrote: > On Thu, 12 Apr 2007, Neil Brown wrote: > > > For the second. > > You say that you " would need at least 96 bits in order to make that > > guarantee; 64 bits of hash, plus a 32-bit count value in the hash > > collision chain". I think 96 is a bit greedy. Surely 48 bits of > > hash and 16 bits of collision-chain-position would plenty. You would > > need 65537 entries before a collision was even possible, and > > billions before it was at all likely. (How big does a set of 48bit > > numbers have to get before the probability that "No subset of 65536 > > numbers are all the same" drops below 0.95?) > > Neil, > you can get a hash collision with two entries.
You need at least 65537 entries before there is any possibility of collision between two "48-bit-hash ++ 16-bit-sequence-number" objects where the 16-bit-sequence-number is chosen to be different from all other 16 bit sequence numbers combined with the same 48 bit hash. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
