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Re: build system option to allow CPU optimizations?
From: |
Ludovic Courtès |
Subject: |
Re: build system option to allow CPU optimizations? |
Date: |
Mon, 20 Dec 2021 18:40:56 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) |
Hi,
Ricardo Wurmus <rekado@elephly.net> skribis:
> Ludovic Courtès <ludovic.courtes@inria.fr> writes:
[...]
> It may very well be the wrong approach in principle, but I also think
> that it’s a neat escape hatch for specific use cases. Separating
> reproducibility patching makes the package transformation mechanism
> more powerful and appealing. Much like respecting TESTS? makes it
> easy for users of modified packages to bypass a failing test suite,
> making patching of Makefiles to remove CPU tuning conditional would
> make for much less complex custom package definitions.
>
>> I found one case though where this is not possible: C++ header-only
>> libraries such as Eigen contain hand-optimized vectorized routines,
>> selected at build time, but we end up compiling Eigen users as the
>> x86_64/AArch64 baseline, which is a waste. (If you do know of other
>> problematic cases, I’m interested in taking a look!)
>>
>> My solution to that is “package multi-versioning” via a
>> transformation
>> option. Hopefully I’ll submit preliminary patches within a week or
>> so!
>
> Oh, exciting!
I forgot to mention it here, but it’s available for testing and probably
even ready to merge:
https://issues.guix.gnu.org/52283
I think it makes an option to dismiss ‘-march’ removal unnecessary; or,
put differently, it achieves the same.
I’m interested in seeing which packages people would mark as “tunable”
and what performance gains it gives!
Thanks,
Ludo’.