Hacking Thy Fearful Symmetry

Hacker, hacker coding bright

A Song of Graph and Report, Part I: A Gathering of Stats

February 2, 2014

Statistics and graphs. They don't always mean much, but they can be so darn mesmerizing.

It's in that optic that I was looking at the Map of CPAN the other day and thought "wouldn't it be cool to have the same view within a distribution?". It's not that I need to do that for anything specific, mind you. But to have a distribution split into territories based on authors and files... Maybe animated throughout different releases, to see the ebbs of contributors and code. I'd be so nifty!

Now, considering that there are many things that can be done with those statistics -- and because I should probably do some real work between bouts of fooling around -- I decided to cut the exercise into different parts. Therefore, today we'll begin with the essential, if a tad dry, step required for everything that will follow. Namely: the gathering of the statistics.

Lay The Blames Around

The good news is that Git already has its git blame sub-command that provide us with a per-line author attribution of the codebase. All we have to do is to interface with it, munge its data to our liking, and we'll be good to go.

To talk to Git, we'll use Git::Repository, with the help of its plugin Git::Repository::Plugin::AUTOLOAD to make things a little neater.

Round Up The Files

So, first step: get the list of the files of the project for a given version tag.

use Git::Repository 'AUTOLOAD';

my $project_dir = '.';
my $version     = 'v1.2.3';

my $git = Git::Repository->new( work_tree => $project_dir );

my @files = sort $git->ls_tree( '-r', '--name-only', $version );

Who Did What?

So far, so good. Now, for every file, we want to have a list of its authors, and how many lines they claim as their own:

my %file_attribution = map { 
    $_ => file_authors( $git, $version, $_ ) 
} @files;

sub file_authors {
    my( $git, $version, $file ) = @_;

    return [
        map { /\(\s*(.*?)\s*\d{4}-/ } $git->blame( $version, $file )

Same Thing, But Compressed

With the code above, we now have an array for each file, holding the name of the author of each line. If we just want to tally the overall contribution of each author, that's slightly overkill, but it'll become handy when we'll be ready to draw the author map of each file.

Still... one entry per line, that's quite verbose. Instead, let's try to scrunch that into a tally of the successive lines associated with the same author:

use List::AllUtils qw/ reduce /;

my %file_attribution = map { 
    $_ => file_authors( $git, $version, $_ ) 
} @files;

sub file_authors {
    my( $git, $version, $file ) = @_;

    return reduce {
        if ( @$a and $a->[-1][0] eq $b ) {
        else {
            push @$a, [ $b, 1 ];
    } [ ], map { /\(\s*(.*?)\s*\d{4}-/ } 
               $git->blame( $version, $file );

Aaaah, yes. Not as dirt-simple as before, but the data structure is now much less wasteful.

Massively Parallel Blaming

Next challenge: git blame is a little bit on the slow side. Not sloth-on-a-diet-of-snails kind of slow, but it does have to spit out all lines of every file. For big projects, that takes a few seconds.

But... isn't our little file_authors() function work in isolation for each file? Wouldn't that be a perfect moment to whip out some parallelization ninja trick? Like... oh, I don't know, try out that neat new MCE module that makes the rounds these days?

use MCE::Map;

my %file_attribution = mce_map { 
    $_ => file_authors( $git, $version, $_ ) 
} @files;

And indeed, with the 4 cores of my faithful Enkidu, the overall script suddenly goes 4 times faster. Considering that all it took was changing a map to a mce_map... yeah, I'll take that.

Sum Everything Up

We now have our raw numbers. Getting the stats per author is now simple bookkeeping:

my $nbr_lines;
my %authors;

for my $x ( map { @$_ } values %file_attribution ) {
    $nbr_lines += $x->[1];
    $authors{$x->[0]} += $x->[1];

# switch into percents
$_ = 100 * $_ / $nbr_lines for values authors;

Put It In A Big Book Of Stats

We'll want to return to those stats, so let's keep them in a file. Let's make it a JSON file. Everybody loves JSON.

use JSON_File;

tie( my %stats, 'JSON_FILE', 'stats.json', pretty => 1 );

$stats{$version} = {
    nbr_lines   => $nbr_lines,
    authors     => \%authors,
    files       => \%file_attribution,

Time To Generate a Report

The numbers are now ours to do as we see fit. Pretty graphical stuff will have to wait for the next installments, but why not create a quick credit roll for the project version we just munged?

use 5.10.0;

use List::AllUtils qw/ part /;

my( $minor, $major ) = part    { $authors{$_} >= 1 } 
                       sort    { $authors{$a} <=> $authors{$b} } 
                       keys    %authors;

my $lines = $nbr_lines;

# 1000000 => 1,000,000 
1 while $lines =~ s/^(\d+)(\d{3})/$1,$2/;

say <

Running that against the latest release of Dancer gives us:


This is the list of all persons who had their hands in
crafting the 32,944 lines of code that make
this version of Dancer, according to `git blame`.

This being said, don't take those statistics too seriously, 
as they are at best a very naive way to judge the contribution 
of individuals.  Furthermore, it doesn't take into account the army 
of equaly important peoples who report bugs, worked on previous
versions and assisted in a thousand different ways. For a glimpse of
this large team, see the CONTRIBUTORS file.

## The Major Hackarna

All contributors claiming at least 1% of the lines of code the project.

    * Alexis Sukrieh                                     30 %
    * franck cuny                                        17 %
    * Sawyer X                                           10 %
    * Damien Krotkine                                     7 %
    * David Precious                                      6 %
    * ambs                                                5 %
    * Yanick Champoux                                     4 %
    * Michael G. Schwern                                  2 %
    * sawyer                                              1 %
    * Alberto Simoes                                      1 %
    * Mark Allen                                          1 %
    * Ovid                                                1 %

## The Minor Hackarna

With contributions of: 

    * mokko
    * Fabrice Gabolde
    * Philippe Bruhat (BooK)
    * Alex Kapranoff
    * LoonyPandora
    * chromatic
    * Anton Gerasimov
    * geistteufel
    * Paul Driver
    * Pedro Melo
    * sdeseille
    * David Moreno
    * Naveed Massjouni
    * Gabor Szabo
    * Rick Myers
    * Alex Kalderimis
    * Sam Kington
    * Max Maischein
    * Colin Keith
    * pdl
    * David Golden
    * JT Smith
    * Flavio Poletti
    * Nate Jones
    * William Wolf
    * Dagfinn Ilmari Mannsåker
    * Stefan Hornburg (Racke)
    * Chris Andrews
    * Kaitlyn Parkhurst
    * Oliver Gorwits
    * Perlover
    * Squeeks
    * Rowan Thorpe
    * CPAN Service
    * John Wittkoski
    * David Steinbrunner
    * Felix Dorner
    * Alessandro Ranellucci
    * Danijel Tasov
    * Al Newkirk
    * Mikolaj Kucharski
    * Kent Fredric
    * Kirk Kimmel
    * Vyacheslav Matyukhin
    * niko
    * Tom Hukins
    * jamhed
    * Franck Cuny
    * Joshua Barratt
    * James Aitken
    * Jesse van Herk
    * rowanthorpe
    * Roman Galeev
    * Marc Chantreux
    * Alex C
    * Martin Schut
    * Naveed
    * Michal Wojciechowski
    * Olof Johansson
    * Naveen
    * Ilya Chesnokov
    * Roberto Patriarca
    * boris shomodjvarac
    * Tom Wyant
    * Lee Carmichael
    * Jacob Rideout
    * Richard Simões
    * Rik Brown
    * Alan Haggai Alavi
    * jonathan schatz
    * Dennis Lichtenthaeler
    * Emmanuel Rodriguez
    * smashz
    * David Cantrell
    * Xaerxess
    * Ask Bjørn Hansen
    * Paul Fenwick
    * Lee Johnson
    * Jonathan "Duke" Leto
    * Tim King
    * Olivier Mengué
    * Brian Phillips
    * Fayland Lam
    * adamkennedy
    * Craig Treptow
    * Jonathan Scott Duff
    * Joel Roth
    * Mark A. Stratman
    * ironcamel
    * John Barrett
    * Brian E. Lozier
    * Florian Larysch
    * Nicolas Oudard
    * Grzegorz Rożniecki
    * Christian Walde
    * Maurice
    * Sebastian de Castelberg
    * scoopio
    * Paul Tomlin
    * François Charlier
    * Anirvan Chatterjee
    * jonasreinsch
    * Neil Hooey
    * Hans Dieter Pearcey
    * Lars Thegler
    * Murray
    * Adam J. Foxson
    * Tatsuhiko Miyagawa
    * sebastian de castelberg
    * Craig
    * Jakob Voss
    * isync
    * Mark Stosberg
    * Assaf Gordon
    * Hagen Fuchs
    * Ivan Paponov
    * Roman Nuritdinov
    * Tom Heady
    * Michael Genereux
    * Duncan Hutty
    * Alfie John
    * Matthew Horsfall (alh)

On Our Next Episode

... things get interesting as we'll tackle transforming those stats into an author-colored map of the distribution. Weeee!

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About the author

Yanick Champoux
Perl necrohacker , ACP writer, orchid lover. Slightly bonker all around. he/him/his