On Tue, Aug 17, 2010 at 6:40 PM, Robert Bradshaw <rober...@math.washington.edu> wrote: > On Tue, Aug 17, 2010 at 6:25 PM, Carl Witty <carl.wi...@gmail.com> wrote: > >> I'm really quite sure that the performance bug was due to a >> Cython-created __getattr__ wrapper. >> >> In detail: when you create a non-cdef subclass of a cdef class with >> __getattr__, Python has to decide what to stick in the tp_getattro >> slot. It notices that there's a __getattr__ defined (that's not a >> Python-created wrapper object), and so it puts in a generic function >> that looks up __getattribute__ and __getattr__ in the type dictionary. >> >> I guess copying __getattribute__ to __getattr__ would slightly change >> the behavior when somebody accessed __getattr__ directly. (It >> wouldn't change the behavior of normal attribute lookup on the >> object.) >> >> With the current cython-devel we could probably fix the Sage >> __getattr__ performance issue by changing Parent and Element to define >> __getattribute__ instead of __getattr__. (Maybe this is what you were >> saying?) > > No, defining __getattribute__ is much worse than defining __getattr__ > because then it needs to call __getattribute__ as an opaque Python > function before invoking the standard Python lookup mechanisms. > > Really, I just need to read some code and do some benchmarks.
In Python, __getattribute__ is much worse than __getattr__. But in Cython, __getattribute__ and __getattr__ both set the tp_getattro slot; so you can replace a __getattr__ with a __getattribute__ that's just about as efficient. In either case, we must avoid having Python call __getattribute__ or __getattr__ as an opaque Python function; that's the source of the performance problem. It's vital that Python calls the tp_getattro slot directly. The way to make that happen is to make sure that any __getattribute__ or __getattr__ definitions are Python-generated wrappers (or, at least, that the wrapper's Py_TYPE is PyWrapperDescr_Type). Carl _______________________________________________ Cython-dev mailing list Cython-dev@codespeak.net http://codespeak.net/mailman/listinfo/cython-dev
