Intermission on the day of the Jessie release

During the “intermission” on the day of the Jessie release, Julien, Ivo, AJ and I spent some time improving Britney2.  Due to said intermission, we can proudly say that from the very first run for Stretch, Britney2 was:

  • running on Python3k.  Kudos to Julien and Ivo.
  • doing consistency checks of identical packages present in two more suites.  Kudos to AJ.
    • Said checking is mostly useful for catching silly mistakes in our test suite.  A very welcome change, as data inconsistency plus hash randomisation (default in Python3k) caused some of the tests to fail sporadically.
    • Also, many thanks to AJ for providing a patch for #709460.  Sadly, I do not remember if we managed to merge that prior to the first Stretch run.
  • outputting some statistics about the “package graph” and some performance counters from its installability tester.

The performance counters are mostly interesting for me, when I mess with the installability tester.  A couple of backtrack related numbers from the Britney run early today:

  • 77 078 times, Britney would create a “full restore point” and recurse.
    • In 10 of those cases, she would reject the guess, backtrack back to the restore point and move on to the next guess.
    • In the remaining 77 068 times, she would accept the candidate (and thereby solve the query).
      • NB: This number is not directly visible and has to be computed manually.  It is possible for Britney to do multiple “accept”-recursions for the same query.
  • 52 times, she would have exhausted all but one option.  In this case, she simply goes “all-in” and skips the restore point.
  • 54 618 times, she would accept the guess using a partial restore point without needing to recurse.
  • An (sadly) uncounted number of times, she would reject the guess using a partial restore point without needing to recurse.

Furthermore, about 82% of the  ~577 000 times Britney called “is_installable” in this run, the installability tester answered with a cached result.  I guess it was a trivial run. 🙂

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