2012/7/3 Stefan Behnel <stefan...@behnel.de> > > Don't forget that cpyext reference counts are quite different from > CPython: > > PySequence_GetItem() needs to *create* a PyObject structure, and the > > returned object has a refcount of 1. > > Then Py_DECREF() will really *deallocate* the PyObject structure... > > Sure. And using PySequence_GetItem() is still some 10x faster in PyPy than > taking a borrowed reference using PyList_GET_ITEM() and then calling > Py_INCREF() on it, which is what Cython does in CPython because it's way > faster there. The overhead of borrowed references is seriously huge in > PyPy. > > BTW, are PyObject structures currently cached in a free-list somewhere? > That would be really helpful for the iteration performance. >
No optimization of any kind have been done in cpyext (it's difficult enough to get it right...) A freelist would be a nice thing, but there would still be the cost of attaching the PyObject to the pypy w_object. Maybe we should use a weak dictionary to cache the PyObject structure. This already exists for objects defined and created from C... > > This is quite more expensive than the simple refcount increment/decrement > > done by CPython. > > > >> OverflowError: array too large > > > > Looks like a ctypes bug to me. Which OS, Python, etc. are you using? > > Ah - totally, sure. I accidentally ran the system Py2.5 on 64bit Linux. > Running it with Py2.7 fixes this specific problem, thanks for the hint! > Although it now names the extension module "nbody.so" instead of > "nbody.pypy-19.so". Comprend qui peut ... > > After figuring out that I was supposed to enable cpyext manually and > running strace to see what extension module name it is actually looking > for, I failed to make it load the module it just built regardless of how I > named it, so I tried building it within the same run as follows: > > pypy/bin/py.py --withmod-cpyext -c 'import setup; import nbody; \ > nbody.test_nbody(1)' build_ext -i Ah, but this won't work! py.py runs on top of CPython, so the PyString_AsString symbol is already defined by your CPython interpreter! There is a workaround though: compile your extension module with python2.7 pypy/module/cpyext/presetup.py setup.py build_ext -i presetup.py will patch distutils, and create a module "nbody.pypy-19i.so" (note the i) which works on top of an *interpreted* pypy. Among the hacks, all symbols are renamed: #define PyString_AsString PyPyString_AsString. Then this should work: pypy/bin/py.py --withmod-cpyext -c "import nbody" *very* slowly of course, but I was able to debug pygames this way! -- Amaury Forgeot d'Arc
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