Ralf Gommers wrote: > On Wed, May 31, 2023 at 12:28 PM Chris Sidebottom chris.sidebot...@arm.com > wrote: > > Matthew Brett wrote: > > Hi, > > On Wed, May 31, 2023 at 8:40 AM Matti Picus matti.pi...@gmail.com wrote: > > On 31/5/23 09:33, Jerome Kieffer wrote: > > Hi Sebastian, > > I had a quick look at the PR and it looks like you re-implemented the > > sin-cos > > function using SIMD. > > I wonder how it compares with SLEEF (header only library, > > CPU-architecture agnostic SIMD implementation of transcendental > > functions with precision validation). SLEEF is close to the Intel SVML > > library in spirit but extended to multi-architecture (tested on > > PowerPC > > and ARM for example). > > This is just curiosity ... > > Like Juan, I am afraid of this change since my code, which depends on > > numpy for sin/cos used for rotation is likely to see large change of > > behavior. > > Cheers, > > Jerome > > I think we should revert the changes. They have proved to be > > disruptive, > > and I am not sure the improvement is worth the cost. > > The reversion should add a test that cements the current user > > expectations. > > The path forward is a different discussion, but for the 1.25 release I > > think we should revert. > > Is there a way to make the changes opt-in for now, while we go back to > > see if we can improve the precision? > > This would be similar to the approach libmvec is taking ( > > https://sourceware.org/glibc/wiki/libmvec), adding the > > `--disable-mathvec` option, although they favour the 4ULP variants rather > > than the higher accuracy ones by default. If someone can advise as to the > > most appropriate place for such a toggle I can look into adding it, I would > > prefer for the default to be 4ULP to match libc though. > > We have a build-time toggle for SVML (`disable-svml` in `meson_options.txt` > and an `NPY_DISABLE_SVML` environment variable for the distutils build). > This one should look similar I think - and definitely not separate Python > API with `np.fastmath` or similar. The flag can then default to the old > (higher-precision, slower) behavior for <2.0, and the fast version for > > =2.0 somewhere halfway through the 2.0 development cycle - assuming the > > tweak in precision that Sebastian suggests is possible will remove the > worst accuracy impacts that have now been identified. > The `libmvec` link above is not conclusive it seems to me Chris, given that > the examples specify that one only gets the faster version with > `-ffast-math`, hence it's off by default.
Argh, I think you're right and I misread it, the --disable-mathvec is for compilation of libc not the actual faster operations which require -ffast-math. Apologies! Cheers, Chris > Cheers, > Ralf _______________________________________________ NumPy-Discussion mailing list -- numpy-discussion@python.org To unsubscribe send an email to numpy-discussion-le...@python.org https://mail.python.org/mailman3/lists/numpy-discussion.python.org/ Member address: arch...@mail-archive.com
