Public bug reported:
GROMACS requires explicitly specifying target SIMD instruction set at
build time. Function multiversioning is not supported. Reference:
https://manual.gromacs.org/2025.3/install-guide/index.html#simd-support
Currently, the amd64v3 package in Questing sets `-march=x86-64-v3` for
C/CXX compiler flags, but still uses GMX_SIMD=SSE4.1. As a result, most
compute-intensive parts of the code don't benefit from new instructions.
I can do performance benchmarks, but the expected improvement is 50+%.
Suggested solution would be to specialize debian/rules to set CMake flag
GMX_SIMD=AVX2_256 when building for amd64v3 variant.
Additionally, this should resolve the error observed when building the
amd64v3 package for Questing.
** Affects: gromacs (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2131605
Title:
Package for amd64v3 is built with SSE4.1 SIMD level
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