Hello list,
I need to understand if there are any specific compilation options set
for the manylinux precompiled binaries, by the packaging system or by
individual python module developers.
We have an image processing application that does certain color
correction, resizing and watermarking of images for a webapp. The
sources are quite large (some as large as 100 megapixels) and the
execution time is very noticeable, some images taking up to a minute to
complete (yes we have post-processing cache, but that initial hit is
crucial).
I have noticed a difference in execution time of our test and production
cases between Linux (Gentoo) and FreeBSD. Takes the same code on FreeBSD
3 times more to process. Investigating further I realized on Linux that
pip is pulling-in already compiled .so libraries, whereas on FreeBSD it
compiles locally (testing with virtualenv and installation with pip).
So when I reinstalled on Linux but ignoring the precompiled .so libs
(with --no-binary :all: given to pip), the execution time shot up 3x
(longer) and equals that of FreeBSD. But, when I recompiled again, but
forcing CFLAGS="-O3" (just tried as a test, and that worked right off
teh bat), the execution time came down to equal the one when installed
from PyPi wheel cache. Same thing happened when I did so on FreeBSD.
So adding -O3 to CFLAGS when building Pillow and ignoring precompiled
libs from wheel cache, improved execution time (of our use case) 3
times!
Now, since -O3 is not a wise thing to do unless you know what you're
doing (and I don't, in this case), I need to find out if that's what was
added to the PyPi wheel cache, or something else, and where was that
defined as I could find no relevant CFLAGS definitions in the Pillow
source code (or maybe it's there but I just can't see it), or in fact
any compilation flags other than -O0 for the test cases.
I also need to understand this so I can force the same compilation
environment for the FreeBSD port of Python Pillow module
(graphics/py-pillow).
Thanks.
--
Vlad K.
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