[gmx-users] Detection for best SIMD instructions failed, using SIMD None

[Jochen Hub]

Hi developers,

cmake is not able to detect that our CPUs support AVX2_256:

-- Detecting best SIMD instructions for this CPU
-- Detection for best SIMD instructions failed, using SIMD - None

This happens on

- Arch Linux
- Gromacs 2018.6 and 2019.1
- cmake version 3.14.1
- with Intel Xeon E5-2643 v4 and Xeon E-2136
- gcc 8.2.1

When specifying manually

cmake -DGMX_SIMD=AVX2_256

all is fine and mdrun runs smoothly with expected performance.

Is this the intended behavior? Is there something we should report to 
find the reason for this behavior?

Thank you,
Jochen

-- 
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Dr. Jochen Hub
Computational Molecular Biophysics Group
Institute for Microbiology and Genetics
Georg-August-University of Göttingen
Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
Phone: +49-551-39-14189
http://cmb.bio.uni-goettingen.de/
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