[gmx-users] avx2 with gcc 4.8.3

[Mark Abraham]

On Mon, Dec 15, 2014 at 2:47 PM, Harry Mark Greenblatt <
harry.greenblatt at weizmann.ac.il> wrote:
>
> BS"D
>
> Dear All,
>
>   While trying to run cmake under Centos 6.6 on a Haswell cpu for Gromacs
> 5.0.3 using gcc 4.8.3, cmake fails claiming the compiler doesn't support
> AVX2, but as far as I know it should...
>
> Cannot find AVX2 compiler flag.  Use a newer compiler, or choose AVX SIMD
>   (slower).
>
> Some tests for AVX2 *do* succeed:
>
> -- Try C compiler AVX2 flag = [-mavx2]
> -- Performing Test C_FLAG_mavx2
> -- Performing Test C_FLAG_mavx2 - Success
> ...
> -- Try C++ compiler AVX2 flag = [-mavx2]
> -- Performing Test CXX_FLAG_mavx2
> -- Performing Test CXX_FLAG_mavx2 - Success
>

Well, which ones fail? Inspecting the compiler output (e.g. using cmake
--debug-trycompile and poking around it its output) is probably the only
way to find that problem.

Mark


> Using  -DGMX_SIMD=AVX_256 does solve the problem, but then I lose AVX2
> acceleration.
>
> I am using CUDA 6.5-19 (which was compiled with gcc 4.4.7, but that
> doesn't seem to be the issue).
>
> Any advice?
>
> Thanks
>
> Harry
>
> Harry M. Greenblatt
> Associate Staff Scientist
> Dept of Structural Biology           harry.greenblatt at weizmann.ac.il
> <mailto:harry.greenblatt at weizmann.ac.il>
> Weizmann Institute of Science        Phone:  972-8-934-3625
> 234 Herzl St.                        Facsimile:   972-8-934-4159
> Rehovot, 76100
> Israel
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