Finishing rebuild of rpms, from deltarpms

[Jonathan Dieter]

On Fri, 2011-04-15 at 22:33 -0700, JD wrote:
> On 04/15/2011 09:04 PM, Andre Robatino wrote:
> > http://cedarandthistle.wordpress.com/2009/11/06/on-binary-delta-algorithms/
> Read the article and parts of the thesis.
> So, the final version of the algorithm
> still remains with the University of Oxford??
> 
> I downloaded the bsdiff  srpm for fc15 and built it.
> 
> I then used it to diff
> -rwxr-xr-x  1 root root 3699072 Feb  6 23:09 
> /boot/vmlinuz-2.6.35.11-83.fc14.i686
> vs
> -rwxr-xr-x  1 root root 3702144 Mar 31 15:26 
> /boot/vmlinuz-2.6.35.12-88.fc14.i686
> and the resulting patch
> -rw-r--r-- 1    root root 3554921 Apr 15 22:17 
> vmlinux-2.6.35.11-83--2.6.35.12-88.patch
> 
> So, you can see that the patch is almost the same size as the files diffed.
> 
> Obviously, version 4.3-8 does not contain the unpublished optimizations
> that Colin Percival mentions in his thesis.

A couple of things:

     1. vmlinuz is compressed and it's essentially useless to delta
        compressed files without uncompressing them first.
     2. We use the program deltarpm to make deltas between rpms.
        Deltarpm uses a modified bsdiff algorithm as well as the add
        block enhancements mentioned in my blog post.

Jonathan
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