[Python-Dev] PEP280 and my experiment

2003年6月14日 03:15:46 +0200

some consideration on PEP 280: Optimizing access to globals
	http://www.python.org/peps/pep-0280.html
after my experiment.
1) in the PEP
"
Description
 (Note: Jason Orendorff writes: """I implemented this once, long
 ago, for Python 1.5-ish, I believe. I got it to the point where
 it was only 15% slower than ordinary Python, then abandoned it.
 ;) In my implementation, "cells" were real first-class objects,
 and "celldict" was a copy-and-hack version of dictionary. I
 forget how the rest worked.""" Reference:
 http://mail.python.org/pipermail/python-dev/2002-February/019876.html)
"
at least now you know there is hope :) for at a minimum some 15% _speedup_
when globals/builtins are heavely involved and a wash when they are not used.
2)
"
 When a function object is created from a code object and a celldict,
 the function object creates an array of cell pointers by asking the
 celldict for cells corresponding to the names in the code object's
 co_globals. If the celldict doesn't already have a cell for a
 particular name, it creates and an empty one. This array of cell
 pointers is stored on the function object as func_cells. When a
 function object is created from a regular dict instead of a
 celldict, func_cells is a NULL pointer.
"
this is probably far from ideal for closures, OTOH with the right 
infrastructure it should be possible to store created caches e.g. in code 
objects and so reuse them.
regards.