[Python-Dev] Slowdown in Python CVS

[Raymond Hettinger]

> > My nightly run of pybench went up from the usual 7590ms per
> > run to around 8200ms between Monday night and today. Can anyone
> > explain this ?
> 
> Did you compare the outputs?  There could be importants hint there!
> :-)
> 
> Maybe this checkin to ceval.c backfired?
> 
> ----------------------------
> revision 2.351
> date: 2003/02/26 18:11:50;  author: rhettinger;  state: Exp;  lines: +18 -4
> Micro-optimizations.
> * List/Tuple checkexact is faster for the common case.
> * Testing for Py_True and Py_False can be inlined for faster looping.
> ----------------------------

That would be a bummer.  It looked like a pure win.

I timed the changes with PyStone with N=200000 and got:
Base Code:      12.379   12.2716   12.2716
+ CheckExact: 12.2746  12.2278   12.3165
+ T/F inlined:  12.108    12.1697   12.1259

Since PyStone does weird things to booleans and uses
"while 1", I ran a separate test on "while 1" vs. "while True"
showed a speedup of "while True" and no measurable
change to "while 1".

If your timings show a different result, let me know and
I'll back it out.


Raymond Hettinger