34 lines
1.4 KiB
Markdown
34 lines
1.4 KiB
Markdown
# OpenMP
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[OpenMP] support was drastically improved in CMake 3.9+. The Modern(TM) way to add OpenMP to a target is:
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```cmake
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find_package(OpenMP)
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if(OpenMP_CXX_FOUND)
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target_link_libraries(MyTarget PUBLIC OpenMP::OpenMP_CXX)
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endif()
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```
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This not only is cleaner than the old method, it will also correctly set the library link line differently from the compile line if needed. In CMake 3.12+, this will even support OpenMP on macOS (if the library is available, such as with `brew install libomp`). However, if you need to support older CMake, the following works on CMake 3.1+:
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```cmake
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# For CMake < 3.9, we need to make the target ourselves
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if(NOT TARGET OpenMP::OpenMP_CXX)
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find_package(Threads REQUIRED)
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add_library(OpenMP::OpenMP_CXX IMPORTED INTERFACE)
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set_property(TARGET OpenMP::OpenMP_CXX
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PROPERTY INTERFACE_COMPILE_OPTIONS ${OpenMP_CXX_FLAGS})
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# Only works if the same flag is passed to the linker; use CMake 3.9+ otherwise (Intel, AppleClang)
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set_property(TARGET OpenMP::OpenMP_CXX
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PROPERTY INTERFACE_LINK_LIBRARIES ${OpenMP_CXX_FLAGS} Threads::Threads)
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endif()
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target_link_libraries(MyTarget PUBLIC OpenMP::OpenMP_CXX)
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```
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{% hint style='danger' %}
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Warning: CMake < 3.4 has a bug in the Threads package that requires you to have the `C` language enabled.
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{% endhint %}
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[openmp]: https://cmake.org/cmake/help/latest/module/FindOpenMP.html
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