Fix: Kokkos 5 performances on AMD

[glesur]

Limit the thread size to avoid register spilling on AMD archs

[glesur]

• Add compiler informations in the logs and in stdout
• allow user to disable fuse multiple adds through the cmake option Idefix_SUPPRESS_FMA (which is compiler-dependent)

[Copilot]

Pull request overview

This PR aims to improve performance on AMD architectures with Kokkos 5 by constraining kernel launch characteristics, and also modernizes build-time metadata (version/compiler info) while adding a configurable way to suppress FMA for cross-architecture validation.

Changes:

• Constrain Kokkos parallel_for range kernels via LaunchBounds<256> in idefix_for wrappers to mitigate AMD register spilling.
• Replace the generated-in-source version.hpp mechanism with CMake-generated headers (version.h, compiler_info.h) and update outputs/version printing to use them.
• Add Idefix_SUPPRESS_FMA and a SuppressFMA.cmake helper to disable FMA contraction across toolchains; update the Python test harness to enable it for bitwise-stable comparisons.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/version.h.in	New template for a generated version header (commit + semantic version strings).
src/compiler_info.h.in	New template for a generated compiler metadata header.
src/output/xdmf.cpp	Switch XDMF header version string source to VersionInfo::version.
src/output/vtk.cpp	Switch VTK header version string source to VersionInfo::version.
src/output/dump.cpp	Switch dump header version string source to VersionInfo::version.
src/input.cpp	Print version via VersionInfo and add compiler metadata output.
src/dataBlock/dumpToFile.cpp	Switch debug dump header version string source to VersionInfo::version.
src/loop.hpp	Apply Kokkos LaunchBounds<256> to range-based parallel_for loops.
pytools/idfx_test.py	Enable Idefix_SUPPRESS_FMA in test CMake invocation for CPU/GPU bitwise consistency.
CMakeLists.txt	Add Idefix_SUPPRESS_FMA, generate headers via configure_file, and wire in suppression helper.
cmake/SuppressFMA.cmake	New module to apply backend/compiler-specific flags to suppress FMA contraction/codegen.

Suppressed comments (2)

CMakeLists.txt:196

• configure_file() writes to ${CMAKE_BINARY_DIR}/build/generated/..., but that directory is never created. On a fresh build tree this will fail at configure time with a "cannot open output file" error. Create the directory once before the first configure_file() call.

configure_file(
    ${CMAKE_SOURCE_DIR}/src/version.h.in
    ${CMAKE_BINARY_DIR}/build/generated/version.h
    @ONLY
)

cmake/SuppressFMA.cmake:76

• The doc comment says the flags are applied "only when the SUPPRESS_FMA option is ON", but this module doesn't define/check that option (the caller currently gates via Idefix_SUPPRESS_FMA). This is misleading if the function is reused elsewhere.

# Applies compiler-specific FMA-suppression flags to <target>'s CXX
# sources, but only when the SUPPRESS_FMA option is ON. Safe to call
# unconditionally.

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