Thanks for trying this out. When I saw your comments, I realized that the difference is due to a speed patch that we have her at CCP. The test was run using current 2.5 python, with a patch applied, as attached this message. The patch was written by me a few years back when I noticed that python spends enormous time during regular run creating exceptions that then get discarded internally. Most of the cost comes from FormatException when it is generating AttributeErrors. So, when I thought I was complaining about slow new objects, I was really showing off my cool optimization.
The problem is, it is difficult to generalize this to python in general. I
spent some time last year to
try to improve new-style classes, by adding ts fields and telling the exception
system to "expect a certain
type of exception, and if it is raised, use PyErr_SetNone() instead of the
PyErr_Format because I will
clear it anyway". I had macros such as
PyErr_Expect(AttributeError);
attr = PyObject_GetAttr(o, a);
PyErr_Expect(0);
if (!attr)
PyErr_Clear()
The problem was, I wasn't able to come up with a simple patch that showed
consistent speed improvements
in the performance testsuite without showing some slowdowns in other places.
Running regular python code through a profiler, and especially code that relies
much on the use of
__getattr__() to emulate attribute access, will show hideous amounts of time
spent formatting
attribute exceptions that get thrown away.
Any thoughts on how to do this better?
And, for completeness, a new test run of this, using python25, first using the
neutered patch version
(where I have set softfail=0 in the relevant places) and then with the patch
active:
import timeit
s = """
class dude:
def bar(self):pass
def __getattr__(self, a): return a
class dude2(object):
def bar(self):pass
def __getattr__(self, a): return a
d = dude()
d2 = dude2()
d.a = d2.a = 1
"""
print timeit.Timer("d.foo", s).timeit()
print timeit.Timer("d.bar", s).timeit()
print timeit.Timer("d.a", s).timeit()
print timeit.Timer("d2.foo", s).timeit()
print timeit.Timer("d2.bar", s).timeit()
print timeit.Timer("d2.a", s).timeit()
patch neutered
1.35734336404
0.157773452422
0.0937950608722
1.48494915604
0.240154539405
0.186524222345
patch active:
0.352850669641
0.147599760073
0.0910020300097
1.4453737036
0.212842069748
0.203442097864
Cheers,
Kristján
> -----Original Message-----
> From: Nick Coghlan [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, October 08, 2008 21:37
> To: Kristján Valur Jónsson
> Cc: Python-Dev
> Subject: Re: [Python-Dev] __getattr__ and new style classes
>
> Kristján Valur Jónsson wrote:
> > Hello there.
> >
> > I‘ve just noticed what I consider a performance problem:
> >
> > Using new style classes to provide attribute-like access using
> > __getattr__ is considerably slower than old style classes: Observe:
>
> I can't reproduce those relative numbers using SVN trunk. Using your
> setup code (copied and pasted directly from your message to my
> interpreter session) I got the following numbers:
>
>
speedpatch.rar
Description: speedpatch.rar
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