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Re: Delta performance

From: Greg Stein <gstein_at_lyra.org>
Date: 2000-10-07 02:18:10 CEST

Um. From a diff'ing neophyte, this seems to beg the question: why don't we
just use diff+gzip instead of spending a bunch of time on a new format?

Cheers,
-g

On Fri, Oct 06, 2000 at 06:56:57PM -0500, Karl Fogel wrote:
> Wow. Pretty interesting.
>
> Thanks for doing these tests -- we should make sure that any format we
> come up with is at least better than gdiff+gzip! :-) (Not to mention
> within shouting distance of vcdiff.)
>
> I think Branko is on Eastern European time, so he probably hasn't seen
> this thread yet.
>
> Greg Hudson <ghudson@mit.edu> writes:
> > Well, I have a little bit of data on differencing performance using my
> > proposed output format. I compared the gcc 2.95 and gcc 2.95.2
> > sources against each other (just the .c files in the gcc subdir), and
> > found:
> >
> > Bytes
> > File-by-file, ours: 15828
> > File-by-file, diff+gzip: 9989
> > Concatenated, ours: 15206
> > Concatenated, diff+gzip: 6015
> >
> > That wasn't too encouraging, so I decided to try some binary data. I
> > tried the .elc files which were present in both emacs 19.34b and emacs
> > 20.7.
> >
> > Bytes
> > File-by-file, ours: 2630361
> > File-by-file, diff+gzip: 2246212
> > Concatenated, ours: 4457134
> > Concatenated, diff+gzip: 2029833
> >
> > That wasn't too encouraging either. I'd like to know whether the
> > problem is with our vdelta code, our window size, or my output format.
> > Unfortunately, Branko does not seem to have had time to debug his
> > generator (it dumps core when you use it, and after I fixed the first
> > bug the next bug looked difficult to fix), so I can't eliminate the
> > output format as a variable. I'm going to write to Phong Vo and ask
> > whether they ever released that library he mentioned the last time I
> > talked to him; maybe that will turn up a good source of comparative
> > data and ideas.
> >
> > (And yes, I reenabled the call to vdelta before running these
> > tests. :) Otherwise it would take a lot more than 15828 bytes to
> > describe how to reconstruct the gcc sources.)

-- 
Greg Stein, http://www.lyra.org/
Received on Sat Oct 21 14:36:10 2006

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