Re: [PATCH] xdiff-interface.c (buffer_is_binary): Remove buffer size limitation

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Dec 4, 2007, 01:00 UTC
Message-ID: <Pine.LNX.4.64.0712040054280.27959@racer.site>
In-Reply-To: <alpine.LFD.0.9999.0712031559480.8458@woody.linux-foundation.org>

Hi,

On Mon, 3 Dec 2007, Linus Torvalds wrote:

Show 8 quoted lines

> On Tue, 4 Dec 2007, Dmitry V. Levin wrote:
> >
> > Average file size in the linux-2.6.23.9 kernel tree is 10944 bytes,
> 
> Don't do "average" sizes. That's an almost totally meaningless number.
> 
> "Average" makes sense if you have some kind of gaussian distribution or 
> similar.

To enhance on that: Gaussian is symmetric, which cannot be the proper distribution for anything that is non-negative.

I see so many mis-applications of statistics/probability theory in my day job that I cannot resist pointing people to the Poisson distribution here (in whose context "average" actually makes kind of sense).

But back to the problem: if you have a truly binary file, then _every_ byte (absent further information, of course) has a probability of 1/256 of being 0.

Which means that if a file is binary, but is unusual enough to have that property only for half of the first 8192 bytes, you get a probability of 1 - 1 / 256^4096 = 1 - 1 / 2 ^ 32768 that the current test succeeds.

I fail to see how this test can possibly fail for the average case.

So if it fails only for special cases, we are probably (in the common, not the mathematical, sense) better off asking those people encountering them to add git-attributes for the files.

IMHO that is not asking for too much.

Ciao, Dscho