Various handle-related changes and improvements

[leofang]

Close#370. Close#433.

• Ensure Program/Linker have consistent .backend and .handle
  • This allows us to add e.g. CXXProgram, PTXProgram, ... in the future without breaking changes (Expose ObjectCode as public API + prune unnecessary input arguments #435 (comment))
• Add get_cuda_native_handle() to fetch the underlying CUDA C object from the corresponding cuda.bindings Python-layer object
  • Recall that for all generated bindings there are 3 layers: Python, Cython, and internal. This refers to the Python layer. The Cython layer provides the C type information (i.e. think of it as a CUDA header)
  • Steps:
    1. Take the Python wrapper object from <some_cuda_core_object>.handle
    2. Pass it to get_cuda_native_handle(), and the underlying C object is returned (no refcount or lifetime management)
  • Since cuda.core is not yet cythonized, this is currently the best solution for Python/Cython/C++ interoperability. Once we lower to Cython we can also apply a similar treatment to all cuda.core objects.
    • This includes implementing ref counting via shared_ptr or other C++ machinery to keep track of lifetime across C++ and Python. We are not there yet.
    • Additional work on cuda.bindings is also needed (Turn all cdef class objects in the Python layer to cdef public class #464)
  • For reviewers of this part: Please focus on these two files (the rest of Cython-related files are direct copy/paste from our existing cuda.bindings infrastructure):
    • tests/cython/test_get_cuda_native_handle.pyx
    • cuda/core/experimental/include/utility.hpp
• some minor doc build fixes

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[leofang]

/ok to test

[leofang]

/ok to test

[leofang]

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[leofang]

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[leofang]

/ok to test

[rwgk]

I only have a few minor comments. I didn't see anything troubling, except the raise vs pass question maybe.

[rwgk]

I only have a few minor comments. I didn't see anything troubling, except the raise vs pass question maybe.

Oh wait, did the except ImportError: raise disappear in the meantime? Please disregard.

[rwgk]

Here it is, I accidentally lost my original comment.

Did you mean to write pass here?

Also, it's safer to make the try-except scope as narrow as possible, e.g. (untested):

 try:
# For each callable in `mod` with name `test_*`,
# wrap the callable in a plain Python function
# and set the result as an attribute of this module.
mod = importlib.import_module(mod)
except ImportError:
pass
else:
for name in dir(mod):
item = getattr(mod, name)
if callable(item) and name.startswith("test_"):
item = py_func(item)
setattr(sys.modules[__name__], name, item)

If there is any tooling that might import this file for analysis: Moving the for loop into a function and using if __name__ == "__main__": could guard against surprises.

[leofang]

This file is copied/pasted from cuda-bindings. I think Vlad (or @shwina? 🙂) was the original author:
https://shwina.github.io/cython-testing/

Did you mean to write pass here?

I suspect the answer was yes (based on Ashwin's blog post) but perhaps it caused some issues, so it was changed to raise? I can see that this is a cheap way to ensure the listed modules must exist and get tested. But then the whole try-except can be removed (or refactored). Perhaps @vzhurba01 can confirm the intention?

In any case, since this is a copy/paste let's change both files in a separate PR.

[leofang]

/ok to test

[leofang]

Note: This approach left a bug uncaught (fixed in commit 37a6850): Ideally, we want to have a cmdline functionality like PyBind11 that returns the header path, something like python -m cuda.core --include-path. Here, we use the header from the local clone of this repo (hence using $SCRIPTPATH) instead of the installed cuda.core package, meaning we do not check if the header is actually packaged (and it was not before the fix). However, I think the said functionality needs to be done in a separate PR...

[leofang]

Example that I added to cuQuantum: https://docs.nvidia.com/cuda/cuquantum/latest/python/api/cuquantum.html#command-line-support

[leofang]

/ok to test

[rwgk]

/ok to test

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