On making Britney smarter

Updating Britney often makes our life easier. Like:

• smooth-updates (winter 2011)
• Adam’s accidental upgrade of the original auto-hinter[1] (winter 2012)
• A non-leaking installability tester (winter 2013)
• Fix non-determinism of easy-hinted smooth updatable packages (summer 2014)
• Support for non-hinted multi-item migrations (autumn 2015)

Concretely, transitions have become a lot easier.  When I joined the release team in the summer 2011, about the worst thing that could happen was discovering that two transitions had become entangled. You would have to wait for everything to be ready to migrate at the same time and then you usually also had to tell Britney what had to migrate together.

Today, Britney will often (but not always) de-tangle the transitions on her own and very often figure out how to migrate packages without help. The latter is in fact very visible if you know where to look.  Behold, the number of manual “easy” and “hint”-hints by RT members per year[2]:

Year | Total | easy | hint
-----+-------+------+-----
2005 |   53  |   30 |  23
2006 |  146  |   74 |  72
2007 |   70  |   40 |  30
2008 |  113  |   68 |  45
2009 |  229  |  171 |  58
2010 |  252  |  159 |  93
2011 |  255  |  118 | 137
2012 |   29  |   21 |   8
2013 |   36  |   30 |   6
2014 |   20  |   20 |   0
2015 |   25  |   17 |   8
2016 |   16  |   11 |   5
2017 |    1  |    1 |   0

As can be seen, the number of manual hints drop by factor of ~8.8 between 2011 and 2012. Now, I have not actually done a proper statistical test of the data, but I have a hunch that drop was “significant” (see also [3] for a very short data discussion).

In conclusion: Smooth-updates (which was enabled late in 2011) have been a tremendous success.

—

[1] A very surprising side-effect of that commit was that the (“original”) auto-hinter could now solve a complicated haskell transition. Turns out that it works a lot better, when you give correct information!

[2] As extracted by the following script and then manually massaged into an ASCII table. Tweak the in-line regex to see different hints.

respighi.d.o$ cd "/home/release/britney/hints" && perl -E '
    my (%years, %hints);
    while(<>) {
        chomp;
        if (m/^\#\s*(\d{4})(?:-?\d{2}-?\d{2});/ or m/^\#\s*(?:\d+-\d+-\d+\s*[;:]?\s*)?done\s*[;:]?\s*(\d{4})(?:-?\d{2}-?\d{2})/) {
             $year = $1; next;
         }
         if (m/^((?:easy|hint) .*)/) {
             my $hint = $1; $years{$year}++ if defined($year) and not $hints{$hint}++;
             next;
         }
         if (m/^\s*$/) { $year = undef; next; }
    };
    for my $year (sort(keys(%years))) {
        my $count = $years{$year};
        print "$year: $count\n"
    }' * OLD/jessie/* OLD/wheezy/* OLD/Lenny/* OLD/*

[3]  I should probably mention for good measure that extraction is ignoring all hints where it cannot figure out what year it was from or if it is a duplicate.  Notable it is omitting about 100 easy/hint-hints from “OLD/Lenny” (compared to a grep -c), which I think accounts for the low numbers from 2007 (among other).

Furthermore, hints files are not rotated based on year or age, nor am I sure we still have all complete hints files from all members.