[Patches] [ python-Patches-560736 ] Optimize list iteration

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Patches item #560736, was opened at 2002-05-26 10:25
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Category: Core (C code)
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Raymond Hettinger (rhettinger)
>Assigned to: Guido van Rossum (gvanrossum)
Summary: Optimize list iteration

Initial Comment:
Filled listobject's tp_iter slot with it's own iterator.  
Speeds looping 5 to 10% (YMMV).

Only half of the speed-up comes from using tp_iter.  
The rest came from code tweaking:
-- eliminate the it variable
-- invert the limit test to avoid jumps
-- bypass the GET_ITEM macro to allow index++ to be 
combined with the lookup.



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>Comment By: Raymond Hettinger (rhettinger)
Date: 2002-05-31 16:07

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Replaced both instances with PyList_Check().
No other changes.
Re-verified compile, timings, and regression tests.

Okay to commit?

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Comment By: Guido van Rossum (gvanrossum)
Date: 2002-05-31 13:07

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Very close. It looks like you are using PySequence_Check()
where you should be using PyList_Check() though, since
listiter_next() really needs it to be a list! (Two place
have this mistake.)

Apart from that, it's good! (Note that the speedup
percentage is better when you use -O. :-)


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