Build with cython

Any cython extension is built by cmake. It first calls cython to convert a pyx file into a C++ file before it is compiled and linked. Using cmake + cython instead of cython only make it easier to link with static libraries and write unit tests in C++.

cmake

The first step is to load the extension FindCython.cmake with find_package(Cython REQUIRED). This file exposes function cython_add_module(name pyx_file omp_lib) called for every extension to build and used as follows:

cython_add_module(
    vector_function_cy                                          # name
    ../onnx_extended/validation/cython/vector_function_cy.pyx   # pyx_file
    OpenMP::OpenMP_CXX                                          # link with this target
    ../onnx_extended/validation/cpu/vector_function.cpp)        # sources files

The function accepts many source files. Other link dependencies can be added as well by adding an instructions like target_link_libraries(name PRIVATE lib_name). This function cythonize the pyx_file into a cpp file before building the dynamic library.

setup.py

setup.py defines a custom command to call cmake. Another line must be added to register the extension in the setup.

if platform.system() == "Windows":
    ext = "pyd"
elif platform.system() == "Darwin"
    ext = "dylib"
else:
    ext = "so"

setup(
    ...
    ext_modules = [
        ...
        CMakeExtension(
            "onnx_extended.validation.cython.vector_function_cy",
            f"onnx_extended/validation/cython/vector_function_cy.{ext}",
        ),
    ]
)