[pypy-dev] Re: [Python-Dev] AST branch update

[Armin Rigo]

Hi Neal,

(CC-ing to pypy-dev, if you don't mind :-)

On Thu, Oct 20, 2005 at 06:11:54PM -0700, Neal Norwitz wrote:
> I was wondering what's going on with PyPy.  How is it going?
> Did you make good progress at the last sprint?

Going quite fine :-)  In the last sprint we added optional
Stackless-style stack manipulation in a couple of days, which I suppose
shows that the approach basically works.

> Any interesting ideas that can be used to improve CPython?

That's an interesting question.  So far PyPy has produced mostly bug
reports for obscure errors and crashes in CPython -- only today, trying
the CPython HEAD with the newly merged AST compiler showed 7 of them :-)

But we are not into language design, and the implementation is
significantly different even at the pure Python level.  It's difficult
to derive direct conclusions so far.  Well, our reference counting
version is twice as slow as the one using the Boehm GC, but as far as I
know it could be all because we are generating faaaaar too many
incref/decref all over the place.  Anyway, someone might want to try
again to scrap Py_INCREF/DECREF and use the Boehm GC with CPython.

I suppose that we will soon try more experiments.  Coming to mind:
unboxed integers to see if they help -- I doubt it, but if they have a
large effect then CPython might consider to use them at least in some
speed-critical places.  Different locking approaches for threads, though
it is unclear how much of what we do there would be practical for
CPython.  Several implementations for app-level string objects, e.g. a
"string slice" one, a "lazily joined substrings" one, etc., which might
give interesting speed-ups for some programs.

All in all I suspect that it will be some more time before we can go
past the current state, which is "being a bit like CPython but not quite
as good".


A bientot,

Armin