[Numpy-discussion] Which generation of s390x CPU and how to change it?

[Matěj Cepl]

Hello,

As a maintainer of Python packages for openSUSE/SUSE,
I would like to ask for help with our bug
https://bugzilla.suse.com/1221902. It seems to us that the latest
version of NumPy suddenly requires z15 CPU generation, although
it used to be OK with z13+ before, and unfortunately that is the
level of the CPU support we standardize in openSUSE.

Is it true? If so, when this change happened and why? How
could we push numpy to work with older processors? Is there
anything more to do than just switch of particular features in
`--cpu-dispatch`?

Thank you for any reply,

Matěj Cepl

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[Numpy-discussion] Re: Which generation of s390x CPU and how to change it?

[Matěj Cepl]

On Mon Mar 25, 2024 at 4:47 PM CET, Ralf Gommers wrote:
> > Is there anything more to do than just switch of particular features in
> > `--cpu-dispatch`?
>
> I suspect not, assuming that that works. If Z13 support is an important use
> case where the performance difference matters a lot, maybe you can bring up
> getting partial or even full support back in NumPy. Most NumPy maintainers
> won't know much/anything about s390x though, so that may require
> contributions and be nontrivial.
>
> Another, more feasible option would be to auto-disable the SIMD features,
> emit a warning, and then continue rather than fail the NumPy build on Z13
> by default.

My colleague Fabian Vogt made a deep debug and found this (see ):

# I found that the test failure here was also
# excluded on 32bit ARM and I dug a bit further:
# https://github.com/numpy/numpy/issues/24548 shows the same reason
# as here. That's when I also noticed the additional info at the
# bottom:
#
# feats  = 'VXE, None'
#
# At first I wasn't able to reproduce it on armv7 because cpu
# feature detection was broken, which nobody noticed... I debugged
# that and fixed it with https://github.com/numpy/meson/pull/12.
#
# After fixing that, I was able to reproduce the test
# failure locally by using NPY_ENABLE_CPU_FEATURES="ASIMDHP,
# None". This wasn't meant to succeed but it did. Fixed with
# https://github.com/numpy/numpy/pull/26151.
#
# Both submitted as
# https://build.opensuse.org/request/show/1163337

Best,

Matěj

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