[Python-Dev] Summary: rejection of 'dynamic attribute' syntax

[Steve Holden]

Ben North wrote:
[...]
> Guido van Rossum wrote:
>> I missed discussion of the source of the 1%. Does it slow down pystone
>> or other benchmarks by 1%? That would be really odd, since I can't
>> imagine that the code path changes in any way for code that doesn't
>> use the feature. Is it that the ceval main loop slows down by having
>> two more cases?
> 
> That seems to be it, yes.  I tested this by leaving the grammar,
> compilation, and AST changes in, and conditionally compiling just the
> three extra cases in the ceval main loop.  Measurements were noisy
> though, as Josiah Carlson has also experienced:
> 
>> I've found variations of up to 3% in benchark times that seemed to be
>> based on whether I was drinking juice or eating a scone while working.
> 
> I'm afraid I can't remember what I was eating or drinking at the time I
> did my tests.
> 
A further data point is that modern machines seem to give timing 
variabilities due to CPU temperature variations even if you always eat 
exactly the same thing.

One of the interesting facts to emerge from the Need for Speed sprint 
last year is that architectural complexities at many levels make it 
extremely difficult nowadays to build a repeatable benchmark of any kind.

> (Thanks also for the kind words regarding my summaries etc.  Having
> caused all the fuss in the first place I felt obliged to try to make
> myself a bit useful :-)
> 
Your management of the discussion process has indeed been exemplary.

regards
  Steve
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