[Python-Dev] Re: [Python-checkins] python/nondist/peps
pep-0329.txt, 1.2, 1.3
jeremy at alum.mit.edu
Thu Apr 22 11:56:57 EDT 2004
On Wed, 2004-04-21 at 10:50, Phillip J. Eby wrote:
> I could be wrong, but it seems to me that globals shouldn't be nearly as
> bad for performance as builtins. A global only does one dict lookup, while
> builtins do two. Also, builtins can potentially be optimized away
> altogether (e.g. 'while True:') or converted to fast LOAD_CONST, or perhaps
> even a new CALL_BUILTIN opcode, assuming that adding the opcode doesn't
> blow the cacheability of the eval loop.
The coarse measurements I made a couple of years ago suggest that
LOAD_GLOBAL is still substantially slower than LOAD_FAST. Less than 100
cycles for LOAD_FAST and about 400 cycles for LOAD_GLOBAL.
It would be good to repeat the measurements with current Python. I
suspect it's a lot harder to figure out where to measure the start and
stop times. The timestamps would need to be integrated with PREDICT and
fast_next_opcode, for example.
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