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Date: Tue, 05 May 2015 17:55:01 -0400
From: Dave Angel <davea@davea.name>
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To: python-list@python.org
Subject: Re: Throw the cat among the pigeons
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On 05/05/2015 05:39 PM, Ian Kelly wrote:
> On Tue, May 5, 2015 at 3:23 PM, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>> On Tue, May 5, 2015 at 3:00 PM, Dave Angel <davea@davea.name> wrote:
>>> def loop(func, funcname, arg):
>>>      start = time.time()
>>>      for i in range(repeats):
>>>          func(arg, True)
>>>      print("{0}({1}) took {2:7.4}".format(funcname, arg, time.time()-start))
>>>
>>>      start = time.time()
>>>      for i in range(repeats):
>>>          func(arg)
>>>      print("{0}({1}) took {2:7.4}".format(funcname, arg, time.time()-start))
>>
>> Note that you're explicitly passing True in one case but leaving the
>> default in the other. I don't know whether that might be responsible
>> for the difference you're seeing.
>
> I don't think that's the cause, but I do think that it has something
> to do with the way the timing is being run. When I run your loop
> function, I do observe the difference. If I reverse the order so that
> the False case is tested first, I observe the opposite. That is, the
> slower case is consistently the one that is timed *first* in the loop
> function, regardless of which case that is.
>

I created two functions and called them with Timeit(), and the 
difference is now below 3%

And when I take your lead and double the loop() function so it runs each 
test twice, I get steadily decreasing numbers.

I think all of this has been noise caused by the caching of objects 
including function objects.  I was surprised by this, as the loops are 
small enough I'd figure the function object would be fully cached the 
first time it was called.

-- 
DaveA