[Cython] porting mpi4py to PyPy runtime

[Stefan Behnel]

Lisandro Dalcin, 02.10.2012 17:06:
> After successfully porting mpi4py to PyPy 1.9, I want to share a few
> issues I've encountered. The most serious onesare on PyPy's side, but
> Cython do require a cuple of very minor fixes.
> [...]
> 4) mpi4py uses @classmethod decorator for many methods in cdef
> classes. I really do not know what's going on, but method lookups do
> not return the classmethod, but the original "unwrapped" method. I've
> found a way to trick it, but again, I have no idea why it is working.
> Basically, I have to execute hasattr() (in Python code, not Cython
> code) on every class method: The hack reduces to adding the following
> code at the very end of Cython code (note that I'm using "exec"):
> 
> if PYPY: exec """
> def _pypy_setup():
>     for klass in (
>         Status,
>         Datatype,
>         Request,
>         Message,
>         Op,
>         Group,
>         Info,
>         Errhandler,
>         Comm,
>         Win,
>         File,
>         ):
>         for name in klass.__dict__:
>             meth = klass.__dict__[name]
>             if (isinstance(meth, classmethod) or
>                 isinstance(meth, staticmethod)):
>                 hasattr(klass, name)
> _pypy_setup()
> del _pypy_setup
> """
> 
> I think (1) and (3) can be trivially handled in Cython, (3) is not an
> issue for Cython as PyBuffer_FillInfo() is not directly used. And
> about (4), we really need help from PyPy folks, they implement
> PyType_Modified() as a non-op
> (https://bitbucket.org/pypy/pypy/src/release-1.9/pypy/module/cpyext/typeobject.py#cl-726)
> but that is not playing well with Cython.

https://bugs.pypy.org/issue1106

I had already opened a ticket for this one a while ago.

Stefan