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Re: Altivec in baseline for ppc64?

On 7/15/21 2:04 PM, Sébastien Villemot wrote:
>> Please go ahead and enabled AltiVec as I don't think it makes much sense to use BLAS
>> on machines without any SIMD support. If any user complains about compatibility issues,
>> please feel free to bring up the issue here again.
> I think I disagree with this idea. OpenBLAS can be pulled in by chains
> of dependencies, even for users who do not even know what BLAS is.
> Violating the baseline can lead to hard-to-understand crashes.

True, but all build servers we have support Altivec.

> Since I think that reliability is more important than performance, I 
> prefer to strictly respect the baseline in the binary package.

Sure. But we could also just have observed whether any people report crashes.

> However note that locally recompiling OpenBLAS is a supported and
> documented procedure, for those who want to take full advantage of
> their hardware.
> Regarding the kernel that is currently built in the official binary, I
> could do with some help to determine which one is the best. You can see
> the list of kernels at this address:
> https://salsa.debian.org/science-team/openblas/-/tree/master/kernel/power
> Each KERNEL.* file lists a bunch of source files, many of which are
> assembly files.
> Currently, I use POWER4 for ppc64 and PPCG4 for powerpc, but I’m unsure
> that those are the right choice. I want a kernel that respects the
> baseline, but still taking advantage of all that is in the baseline.

I would have to look into that with more detail. We can probably also
discuss this on the #debian-ports IRC channel.


 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz@debian.org
`. `'   Freie Universitaet Berlin - glaubitz@physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

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