Martin v. Löwis wrote: > 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.bat for what > used > to be part of the release process. It takes quite some time, but it rebuilt > more > than 1% (IIRC).
That's almost certainly the case. I didn't run anywhere near enough to call it good, though I'd only really expect the size to get worse and the speed to get better. > FWIW, I stopped using PGO for the official releases when it was demonstrated > to > generate bad code. In my experience, a compiler that generates bad code has > lost > trust "forever", so it will be hard to justify re-enabling PGO (like "but it > really works this time"). I wasn't sad when I found a justification to skip > the > profiling, since it significantly held up the release process. Yeah, and it seems the bad code is still there. I suspect it's actually due to optimizing for space rather than speed, and not due to PGO directly, but either way I'll be trying to get it fixed. [EARLIER EMAIL] > By "keep around", I'd be fine with "in a subdirectory of PC". PCbuild should > either switch for sure, or not switch at all. People had proposed to come up > with a "PCbuildN" directory (N=10, N=14, or whatever) to maintain two build > environments simultaneously; I'd be -1 on such a plan. There needs to be one > official toolset to build Python X.Y with, and it needs to be either VS 2010 > or > VS 2014, but not both. That's what I have planned. Right now it's in my sandbox and I've just replaced the existing PCbuild contents (rather wholesale - I took the opportunity to simplify the files, which is important to me as I spend most of my time editing them by hand rather than through VS). When/if I merge, the version in PC\VS10.0 will be exactly what was there at merge time. > Regards, > Martin And thanks, I appreciate the context and suggestions. Cheers, Steve _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
