Subject: Re: [PATCH 0/6] Compute and consume generation numbers

From: Jakub Narebski <[email-masked]>
Date: Sat, 07 Apr 2018 18:55:48 +0200

Hello,

Derrick Stolee <[email-masked]> writes:

> This is the first of several "small" patches that follow the serialized
> Git commit graph patch (ds/commit-graph).
>
> As described in Documentation/technical/commit-graph.txt, the generation
> number of a commit is one more than the maximum generation number among
> its parents (trivially, a commit with no parents has generation number
> one).
>
> This series makes the computation of generation numbers part of the
> commit-graph write process.
>
> Finally, generation numbers are used [...].
>
> This does not have a significant performance benefit in repositories
> of normal size, but in the Windows repository, some merge-base
> calculations improve from 3.1s to 2.9s. A modest speedup, but provides
> an actual consumer of generation numbers as a starting point.
>
> A more substantial refactoring of revision.c is required before making
> 'git log --graph' use generation numbers effectively.

I have started working on Jupyter Notebook on Google Colaboratory to
find out how much speedup we can get using generation numbers (level
negative-cut filter), FELINE index (negative-cut filter) and min-post
intervals in some spanning tree (positive-cut filter, if I understand it
correctly the base of GRAIL method) in commit graphs.

Currently I am at the stage of reproducing results in FELINE paper:
"Reachability Queries in Very Large Graphs: A Fast Refined Online Search
Approach" by Renê R. Veloso, Loïc Cerf, Wagner Meira Jr and Mohammed
J. Zaki (2014).  This paper is available in the PDF form at
https://openproceedings.org/EDBT/2014/paper_166.pdf

The Jupyter Notebook (which runs on Google cloud, but can be also run
locally) uses Python kernel, NetworkX librabry for graph manipulation,
and matplotlib (via NetworkX) for display.

Available at:
https://colab.research.google.com/drive/1V-U7_slu5Z3s5iEEMFKhLXtaxSu5xyzg
https://drive.google.com/file/d/1V-U7_slu5Z3s5iEEMFKhLXtaxSu5xyzg/view?usp=sharing

I hope that could be of help, or at least interesting
--
Jakub Narębski