Summer of Code 2008 project application draft: Pack v4

Dear Git community,

Here is a draft of my application for the Google Summer of Code 2008. I am aware, that this is a big project, so how might the scope be limited, so that the work is still useful to build on top of? How about just rebasing the patches already in the sp/pack4 branch in the fastimport.git repository?

The application text goes like this:

" The project goal is to rebase the code and ideas developed for the version 4 of the git pack format, which showed good promise of making packs smaller, and faster.

The ideas of a new even more optimized pack format has been floating around the git world for almost two years, and because of the rapid pace of development the code implementing those ideas has become less, and less ready for inclusion in mainline.

Since those patches touch so many of the core functions in git, it will be a good chunk of work getting them mergeable, and nobody has gotten around to doing that yet. This will be a good oppertunity for laying the ground work, and getting the ball rolling again.

This project will not only benefit Git itself, but also the nummerous projects, and developers using Git as their prefered revision control system, among them many prominent open source and free software projects.

About me: I have been following the development of Git on and of almost from the beginning, and have been trying to learn from its design, and implementation, and especially I have been interested in implementation of the git repository, index, and pack format. I have contributed a few general clean-up patches, but I have not yet had the chance (read time) to really dive in, and make a significant, and non-trivial contribution, although I would have liked to. "

Comments?

Regards,

Peter

Peter Eriksen <s022018@student.dtu.dk> wrote:

...

Have you had a chance to look at those patches yet? Or the code that they touch, but which has been heavily modified since then (like say builtin-pack-objects.c)?

I would hope that forward-porting those patches would only take us through to about the mid-term, and then finishing out the bulk of the series (like commit dict encoding, maybe dict of object ids used in trees) would be the remainder of the summer. But that may be aggressive. To be successful I think the student working on this project needs to spend some time during the bonding period to understand the current pack v2 format and how the pack v4 format was going to address some of the shortcomings of v2.

To some extent I have left the design details about pack v4 off
the ideas page hoping to draw students into explaining their own
ideas for how to improve upon Git's pack data storage.  Even if the
student's ideas provide less compression than pack v4 was hinting
it can give us, it shows the student's ability to think through
the problem and their desire to work on the project.  Its also why
I called it "v4/v5"... some of the students own ideas may be novel
to us and better than v4, hence creating a v5...
 

On Mon, Mar 31, 2008 at 12:12:17AM -0400, Shawn O. Pearce wrote:

Yes, more than a year ago, see e.g. http://thread.gmane.org/gmane.comp.version-control.git/43016 but I will need to refresh my memory.

No, I am not yet too familiar with all the newest changes. I obviously would need to read that code carefully.

I will think a bit about this, and try to make a time line.

Yes, since I basic understanding of the pack formats some time ago, it should be possible to get up to speed fairly quickly in the bonding period.

This would be nice of course, but my time is quite limited at the moment, so this will not be possible for me yet. The reason why I would like to participate this year is because my summer vacation this year will be much earlier, and will fit very well into the GSoC window.

Thank you for comments.

Peter