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Update CMake to support newer GPU architectures #4572

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Update CMake to support newer GPU architectures #4572

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03f713f
trying to make build system work with Blackwell
samuelpmish Jul 2, 2025
e218282
Merge branch 'development' of github.com:samuelpmish/amrex into devel…
samuelpmish Jul 17, 2025
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12 changes: 1 addition & 11 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
cmake_minimum_required(VERSION 3.18)
cmake_minimum_required(VERSION 3.24)

#
# Setting a cmake_policy to OLD is deprecated by definition and will raise a
Expand All @@ -24,16 +24,6 @@ if(POLICY CMP0127)
cmake_policy(SET CMP0127 NEW)
endif()

#
# CMake 3.18+: CMAKE_CUDA_ARCHITECTURES
# https://cmake.org/cmake/help/latest/policy/CMP0104.html
# We have to migrate there, but maybe the new "native" option (CMake 3.24+)
# is what we want to wait for:
# https://cmake.org/cmake/help/v3.24/prop_tgt/CUDA_ARCHITECTURES.html
if(POLICY CMP0104)
cmake_policy(SET CMP0104 OLD)
endif()

#
# Prevent in-source builds
#
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11 changes: 1 addition & 10 deletions Tools/CMake/AMReXCUDAOptions.cmake
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Expand Up @@ -17,16 +17,7 @@ endmacro ()
#
message(STATUS "Enabled CUDA options:")

set(AMReX_CUDA_ARCH_DEFAULT "Auto")
if(DEFINED CMAKE_CUDA_ARCHITECTURES)
set(AMReX_CUDA_ARCH_DEFAULT "${CMAKE_CUDA_ARCHITECTURES}")
endif ()
if(DEFINED ENV{AMREX_CUDA_ARCH})
set(AMReX_CUDA_ARCH_DEFAULT "$ENV{AMREX_CUDA_ARCH}")
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@ax3l ax3l Jul 24, 2025

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Let us keep that $ENV{AMREX_CUDA_ARCH} hint to avoid breakage for users.

If found, we simply set the default for CMAKE_CUDA_ARCHITECTURES to it.

endif()
set(AMReX_CUDA_ARCH ${AMReX_CUDA_ARCH_DEFAULT} CACHE STRING "CUDA architecture (Use 'Auto' for automatic detection)")

option(AMReX_CUDA_FASTMATH "Enable CUDA fastmath" ON) # Note: inconsistent with AMReX_FASTMATH defaults
option(AMReX_CUDA_FASTMATH "Enable CUDA fastmath" ON)
cuda_print_option( AMReX_CUDA_FASTMATH )

set(AMReX_CUDA_MAXREGCOUNT "255" CACHE STRING
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10 changes: 8 additions & 2 deletions Tools/CMake/AMReXParallelBackends.cmake
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Expand Up @@ -109,8 +109,14 @@ if ( AMReX_GPU_BACKEND STREQUAL "CUDA"
)
endforeach()

# Take care of cuda archs
set_cuda_architectures(AMReX_CUDA_ARCH)
# default to building for the architecture of the available GPU
set(AMREX_CUDA_ARCHS native)
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@ax3l ax3l Jul 24, 2025

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Great!


# but, if the user specifies architectures explicitly then use that instead
if (DEFINED CMAKE_CUDA_ARCHITECTURES)
set(AMREX_CUDA_ARCHS ${CMAKE_CUDA_ARCHITECTURES})
endif()

foreach(D IN LISTS AMReX_SPACEDIM)
set_target_properties(amrex_${D}d
PROPERTIES
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