From: Morten Welinder <mwelinder@gmail.com>
To: Rob Jellinghaus <robj@unrealities.com>
Cc: git@vger.kernel.org
Subject: Re: Val Henson's critique of hash-based content storage systems
Date: Fri, 29 Apr 2005 16:47:17 -0400 [thread overview]
Message-ID: <118833cc0504291347ea1a3fa@mail.gmail.com> (raw)
In-Reply-To: <loom.20050429T015434-928@post.gmane.org>
On 4/28/05, Rob Jellinghaus <robj@unrealities.com> wrote:
> I assume most people here have read this, but just in case:
>
> http://www.usenix.org/events/hotos03/tech/full_papers/henson/henson.pdf
The math in section 3 is bogus. 1-(1-2^-b)^n isn't hard to compute and
even if it was, it is the wrong formula. (Set n==2^b; you obviously should
get probability 1 for collision.)
The right formula is 1-B!/B^n/(B-n)! where B=2^n. For n=2^80 and b=160
you get about 39%.
Morten
prev parent reply other threads:[~2005-04-29 20:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-29 0:06 Val Henson's critique of hash-based content storage systems Rob Jellinghaus
2005-04-29 19:45 ` Linus Torvalds
2005-04-29 19:52 ` Tom Lord
2005-04-29 20:17 ` C. Scott Ananian
2005-04-29 20:37 ` Tom Lord
2005-04-29 20:41 ` C. Scott Ananian
2005-04-29 20:14 ` H. Peter Anvin
2005-04-29 20:47 ` Morten Welinder [this message]
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