swmm-python fails to compile in Apple M1

[abhiramm7]

Hi all,

swmm-python fails to compile in M1 Macs. It seems to be an openmp issue. Digging more into it, I've discovered that llvm does not yet fully support openmp (see seq-lang/seq#248 (comment)). The same issue seems to persist with gcc as well.

I found two ways to address this issue:

1. Compile with set(CMAKE_OSX_ARCHITECTURES "x86_64")
2. Disable openmp in CmakeLists

Though 1 works, it would need x86_64 python installed. For now I think 2 might be the best option. We would just have to update cmakelists file.

# If wheel build on Apple fetch and build OpenMP Library
if (APPLE AND (NOT CMAKE_OSX_ARCHITECTURES STREQUAL "arm64"))
    include(./extern/openmp.cmake)
else()
    find_package(OpenMP
        OPTIONAL_COMPONENTS
            C
    )
endif()

I'll keep looking for a way to support openmp on m1 Macs. For now, I am able to compile swmm-python and run pyswmm without openmp.

[michaeltryby]

@abhiramm7 if you refer to homebrew recipe for libomp you can see that they are supporting M1 macs. I would recommend upgrading to libomp v13 like they do. Currently we build v11.1.

[abhiramm7]

Oh cool. I am using v13 libomp. May be my compiler is not seeing the libomp, I'll dig into it. Thanks @michaeltryby :)

[michaeltryby]

@abhiramm7 swmm-toolkit wheel builds its own version of libomp for binary compatibility with Python. Refer to external/openmp.cmake

[michaeltryby]

Deployment target for Python on X86_64 Mac is 10.9. Doesn’t make sense on an M1 Mac though …

[michaeltryby]

Helpful discussion

https://discuss.python.org/t/providing-binary-packages-for-apple-m1/9288/5

[michaeltryby]

This is actually a significant task involving a port of SWMM to a new processor. I would be wise to establish a new set of benchmarks for the SWMM build

[karosc]

this is resolved by SWMM #403 and swmm-toolkit #122