AVX and AVX512 instruction detection

[blais...@gmail.com]

Dear all,

I hope you are well.

I was wondering if there was anything specific that had to be done to enable deal.II to leverage AVX and AVX512 instructions on intel processors?

By default, it seems that on my intel machine, these vectorization instructions are not detected, e.g.:

-- Performing Test DEAL_II_HAVE_SSE2
-- Performing Test DEAL_II_HAVE_SSE2 - Success
-- Performing Test DEAL_II_HAVE_AVX
-- Performing Test DEAL_II_HAVE_AVX - Failed
-- Performing Test DEAL_II_HAVE_AVX512
-- Performing Test DEAL_II_HAVE_AVX512 - Failed
-- Performing Test DEAL_II_HAVE_ALTIVEC
-- Performing Test DEAL_II_HAVE_ALTIVEC - Failed

However, I can see that avx  is a supported set of instruction on my processor by looking at /proc/cpuinfo.

Is there something I am missing that needs to be done to enable full support of vectorization instruction?

Best :)
Bruno

[Wolfgang Bangerth]

Bruno,
I believe that you need to configure with
-DDEAL_II_ALLOW_PLATFORM_INTROSPECTION=ON to enable compiling with more
than what the basic platform (in your case, x86_64) guarantees.

Best
W.

On 4/20/22 05:50, blais...@gmail.com wrote:
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--
------------------------------------------------------------------------
Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

[Matthias Maier]

Hi Bruno,

You'll have to explicitly enable the instruction set with your
CXXFLAGS. For example, by compiling via

$ cmake -DDEAL_II_CXX_FLAGS="-march=native" [...]

Best,
Matthias