[gmx-users] FFTW with AVX

[Mark Abraham]

Hi,

No,
http://manual.gromacs.org/documentation/5.1.1/install-guide/index.html#using-fftw
is
consistent - use both --enable-sse2 and --enable-avx. Earlier documentation
was incomplete - the important thing is that even if the hardware is AVX,
with up to and including FFTW 3.3.4, performance is best if FFTW is
configured with both SSE and AVX support (and the latter tends to be only
of minor importance).

Mark

On Mon, Jan 4, 2016 at 2:36 PM Oliver Schillinger <
o.schillinger at fz-juelich.de> wrote:

> Hi there,
> I just noticed that when I compile gromacs 5.1.1 with
> GMX_BUILD_OWN_FFTW=ON, it compiles fftw with avx support (at least that
> is what cmake reports: "The GROMACS-managed build of FFTW 3 will
> configure with the following optimizations: --enable-sse2;--enable-avx").
> However, in the online installation instructions it is noted that avx
> might slow down the computation and its use is discouraged.
> Is this information outdated or are the defaults that gromacs uses for
> the fftw compilation not optimal (and how do I change them)?
> Cheers,
> Oliver
>
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> Oliver Schillinger
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