[IronPython] IPy2b5 Performance

[Asaf Kleinbort]

Thanks for the quick reply.

Today we do many 'little' sorts,  since we have a sort call in an object's
__init__. However we might be able to avoid it. 

I do not understand what constitutes a distinct call site. Can you give some
more details on this?

 

From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt Hagenlocher
Sent: Tuesday, October 07, 2008 5:40 PM
To: Discussion of IronPython
Subject: Re: [IronPython] IPy2b5 Performance

 

Every time you call sort, we create a new call site object which needs to be
spun up.  So your test is really an absolute worst-case as far as
performance goes.  Is it actually reflective of the circumstances under
which you do sorting, where the number of sorts vastly exceeds the size of
each sort?

 

We could reuse the sort call site instead of creating a new one for each
sort, but that comes with its own problems.

 

Exceptions are relatively slow in the CLR, which is why it's best to use
them only for actual exceptions and not for the failure path of a
comparison.  In the example you give, the "best" code is probably
"getattr(obj, 'prop', 0)".

 

On Tue, Oct 7, 2008 at 8:15 AM, Asaf Kleinbort <asaf at itstructures.com>
wrote:

Hi all,

I am investigating performance problems we have when running our code using
IPy2b5 (comparing to IPy 1.1.1).

Found two interesting issues:

1.       It seems that there is some bug in the 'sort' method

Running the following code:

 

from System import DateTime

def test():

    s = DateTime.Now

    for i in xrange(100000):

        a = [1,4,7,6,10,6]

        a.sort()

    return (DateTime.Now - s).TotalMilliseconds

            print test()

 

we get 3900% (!) degradation between IP1 and IPy2b5:  In IPy 1 the code runs
in 390ms and in IPy2b5: 15281ms

 

2.This is probably already known:  there is a major difference in
performance between an if/else block and a try/catch one:

        def func1(obj):

            try:

                return obj.prop

            except:

                return 0

       

                 def func2(obj):

            if hasattr(obj,'prop'):

                return obj.prop      

            else:

                return 0

 

        def test(s):

                     for i in xrange(100000):

                x = func1(set())

            return (DateTime.Now -s).TotalMilliseconds

        

        def test2(s):

            for i in xrange(10000):

                x = func2(set())

            return (DateTime.Now -s).TotalMilliseconds

                  

                 print test(DateTime.Now)

                 print test2(DateTime.Now)

                

Results for IPy1 and IPy2b5 are similar ~3000ms for 'test' and ~15ms for
'test2'. Using if/else is 200 times quicker. 

In Cpython it is only 2 times quicker.

 

We can bypass the second issue in our code, but the first one is harder to
ignore.

Are these issues already known? Any ideas? 

Thanks,

Asaf

 

 


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