Tuesday, February 18, 2014

Py3k status update #13

This is the 13th status update about our work on the py3k branch, which we
can work on thanks to all of the people who donated to the py3k proposal.

We're just finishing up a cleanup of int/long types. This work helps the py3k
branch unify these types into the Python 3 int and restore JIT compilation of
machine sized integers

This cleanup also removes multimethods from these types. PyPy has
historically used a clever implementation of multimethod dispatch for declaring
methods of the __builtin__ types in RPython.

This multimethod scheme provides some convenient features for doing this,
however we've come to the conclusion that it may be more trouble than it's
worth. A major problem of multimethods is that they generate a large amount of
stub methods which burden the already lengthy and memory hungry RPython
translation process. Also, their implementation and behavior can be somewhat

The alternative to multimethods involves doing the work of the type checking
and dispatching rules in a more verbose, manual way. It's a little more work in
the end but less magical.

Recently, Manuel Jacob finished a large cleanup effort of the
unicode/string/bytearray types that also removed their multimethods. This work
also benefits the py3k branch: it'll help with future PEP 393 (or PEP 393
) work. This effort was partly sponsored by Google's Summer of
Code: thanks Manuel and Google!

Now there's only a couple major pieces left in the multimethod removal (the
float/complex types and special marshaling code) and a few minor pieces that
should be relatively easy.

In conclusion, there's been some good progress made on py3k and multimethod
removal this winter, albeit a bit slower than we would have liked.


1 comment:

Armin Rigo said...

The str/unicode/bytearray refactoring is not completely done yet.