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Re^6: [OT] The statistics of hashing. (formula)

by BrowserUk (Pope)
on Apr 01, 2012 at 21:56 UTC ( #962936=note: print w/replies, xml ) Need Help??


in reply to Re^5: [OT] The statistics of hashing. (formula)
in thread [OT] The statistics of hashing.

If you could distill your write-up to a formula, that would be helpful. -- I already did that

I guess that your idea of a formula and mine are different.

where $b1 is the number of bits set in the first vector.

The "number of bits set" in each vector at any given insert is entirely dependent upon not just how many, but what values have already been inserted.

Which means that to use your description to calculate the probabilities, I would need to iterate the entire thing and count the number of bits set in each vector at each iteration. And then those "calculated probabilities" would only be applicable to that particular sequence of inserts.

At which point, I might just as well just record the actual numbers of false positives, rather than calculate them.

You'll no doubt come back and tell me that I've completely misunderstood you (again), and that everything I need to know is right there if I would only read you correctly.

Thank you for your attempts to assist me.


With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

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Re^7: [OT] The statistics of hashing. (formula)
by tye (Sage) on Apr 01, 2012 at 22:17 UTC
    You'll no doubt come back and tell me that I've completely misunderstood you (again)

    I never said that you completely misunderstood me. But I'll take your apparent lack of interest and leave it at that.

    - tye        

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