ideas for C optimization wanted

[David Ingamells]

Reminds me of the time when I used to code in Fortran and stepped down 
to assembler to speed-up the critical bits! I also remember that 
choosing the right small bits of code to rewrite in assembler gave very 
significant speed-ups.

One word of caution: by adding some compiled code to bzr you are 
doubling (actually more) the complexity of the build and release of the 
code. Presently I can just run core bzr "out-of-the-box" from the dev 
branch, but if bits are in C that won't be possible any more. I strongly 
recommend that you take some time to get the build side of things sorted 
before you go too far down the C path. A bit of effort in that area now 
will save lots of grief later.

good luck!

Martin Pool wrote:
> Tim said to me he was interested in doing some C or Pyrex code to
> speed up Bazaar, and asked for suggestions on where to begin.
>
> One that comes to mind for me would be changing some of the larger
> performance-critical functions in workingtree_4.py (like
> InterDirStateTree.iter_changes) to have a simple Python implementation
> and a fast C implementation.  Some of them are pretty long, partly
> because of wanting to avoid python function-call overhead.   But it
> would be a good idea to do some profiling with lsprof first and see if
> they are actually near the top in current code.  You should make sure
> lsprof is installed and working before going offline.
>
> There are some notes here
> <http://doc.bazaar-vcs.org/bzr.dev/developers/profiling.html> on how
> to profile Bazaar and in
> <http://doc.bazaar-vcs.org/bzr.dev/en/developer-guide/HACKING.html> on
> development generally, including writing C extensions.
>
> Another thing that would be good but might be beyond the time
> available would be to bind in xdelta or another binary format into a
> new repository format.
>
>