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[Python-Dev] Python 3.5 on VC14 - update
"Martin v. Löwis"martin at v.loewis.de
Wed Jun 11 00:24:48 CEST 2014
Am 10.06.14 18:30, schrieb Steve Dower:> I ran a quick test with profile-guided optimization (PGO, pronounced> "pogo"), which has supposedly been improved since VC9, and saw a very> unscientific 20% speed improvement on pybench.py and 10% size> reduction in python35.dll. I'm not sure what we used to get from VC9,> but it certainly seems worth enabling provided it doesn't break> anything. (Interestingly, PGO decided that only 1% of functions> needed to be compiled for speed. Not sure if I can find out which> ones those are but if anyone's interested I can give it a shot?)You probably ran too little Python code. See PCbuild/build_pgo.batfor what used to be part of the release process. It takes quite sometime, but it rebuilt more than 1% (IIRC).FWIW, I stopped using PGO for the official releases when it wasdemonstrated to generate bad code. In my experience, a compilerthat generates bad code has lost trust "forever", so it will behard to justify re-enabling PGO (like "but it really works thistime"). I wasn't sad when I found a justification to skip theprofiling, since it significantly held up the release process.Regards,Martin
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