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From: ludovic.courtes@inria.fr (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: fftw runtime cpu detection
Date: Fri, 06 Apr 2018 10:05:43 +0200
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References: <20180405221329.GT105827@pe06.us.cray.com>
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In-Reply-To: <20180405221329.GT105827@pe06.us.cray.com> (Eric Bavier's message
	of "Thu, 5 Apr 2018 17:13:29 -0500")
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To: Eric Bavier <bavier@cray.com>
Cc: guix-devel@gnu.org

Hello Eric,

Eric Bavier <bavier@cray.com> skribis:

> I recently discovered that the FFTW library can do runtime cpu
> detection.  In order to do this, the package needs to be configured to
> build SIMD "codelets", like how our 'fftw-avx' currently does.  Then,
> based on the instruction support detected at runtime, make those
> kernels available to the fftw "planner" for execution.

That=E2=80=99s really good news!  Thanks for testing it.

The patch LGTM.  Can you confirm that the planner won=E2=80=99t ever try to=
 use
the AVX2 codelets, for instance when running the test suite on an x86_64
box that lacks AVX2?

If that=E2=80=99s the case, I=E2=80=99d be in favor of pushing this patch t=
o core-updates.

Thanks,
Ludo=E2=80=99.