[PATCH 00/11] C++26 [simd]

[Matthias Kretz]

Hi,

I think that should be possible. bit and math is trivial to exclude. 
simd_complex.h is trivial. The parts in simd_mask.h and simd_vec.h are 
slightly harder but likely not a big deal. I should be able to not remove too 
much — I can't guarantee that I remove everything that could be removed.

In any case, it's a challenge to continue implementation of [simd] (the 
missing sections and support for ARM and POWER) while implementing PR 
feedback. Making the PR smaller could make that easier or harder, I can't say.

I'll push a new set of branches to my fork and will open a new PR. Unless you 
object, that PR will be a single commit of the reduced feature set. I'd also 
implement as much of your feedback as I can do quickly. After pushing the 
implementation I'll work on a small set of tests.

Wrt tests, can you point me to
- in what directory they should go,
- the naming convention to use,
- your recommendation of a test to learn/copy from.

I think I still know how to disable the tests for pre-C++26 and non-x86.

Oh, and I looked at bits/version.* and I'm not sure I got it yet. I would 
modify bits/version.def, include <bits/version.h> from std/simd (and not from 
any of the bits/simd_*.h files) and then make inclusion of bits/simd_*.h 
conditional on __glibcxx_simd. That's it? Topological sort means simd simply 
goes at the end of the file for now?

- Matthias


Tomasz Kaminski [Monday, 13 October 2025, 18:11:59 CEST]:
> Hi,
> 
> I have looked throu the patches, and my preference would be to split the
> work on simd,
> into the chunks that get reviewed and landated into the trunk branch. So
> multiple patch series.
> This will require some effort on your part into reshuffling the comments,
> so I would like to hear
> your opinion on that first.
> 
> With the mdspan, we have worked by having an internal feature test macro
> exposed with value
> one (so no_stdname in version.def), until we have complete implementation.
> 
> What i would suggest would be to have:
> 1) simd::vec, simd::mask and basic math ops for integral/floating point
> types,
>     a difference here from existing patches would be that we will not
> include
>     parts related to complex (bit_mask handling, _M_complex functions from
> basic_simd_vec)
> 2) bit operations for simd
> 3) math operations for simd
> 4) simd from complex
> 
> I have also realized that the patches do not include any test for simd,
> this make is very hard
> to review, as I do not have any example to check, work on. So having some
> minimal test suite
> in repo would be valuable from a review point.
> 
> Again, this will make the submission less convenient on your end, so please
> let me know if that
> is workable. If not I will try to continue on the forge in the form we have
> currently.
> 
> On Fri, Oct 10, 2025 at 5:40 PM Matthias Kretz <m.kretz@gsi.de> wrote:
> > Tomasz Kaminski [Friday, 10 October 2025, 17:18:15 CEST]:
> > > No need to do it when the patch is available on forge. We can iterate
> > 
> > there.
> > 
> > Do you prefer if I add commits and rebase/squash/fixup only when we're
> > done,
> > or do you prefer if I force-push changes?
> > 
> > Also, should I simply keeping the mailing lists up to date by writing a
> > mail
> > to this thread whenever the forge's PR needs re-review?
> > 
> > --
> > ──────────────────────────────────────────────────────────────────────────
> > 
> >  Dr. Matthias Kretz                           https://mattkretz.github.io
> >  GSI Helmholtz Center for Heavy Ion Research               https://gsi.de
> >  std::simd
> > 
> > ──────────────────────────────────────────────────────────────────────────


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 Dr. Matthias Kretz                           https://mattkretz.github.io
 GSI Helmholtz Center for Heavy Ion Research               https://gsi.de
 std::simd
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