GT4Py programs as DaCe SDFGConvertibles

[kotsaloscv]

This feature is needed for implementing DaCe orchestration, e.g. in ICON4Py.

[havogt]

Just a general comment, I am wondering if DaCe offers alternatively the option to register the conversion functions, instead of having to make them part of the object. (E.g. like jax pytrees work) If only the current option is available I am wondering if we should go with a monkey patching approach to remove the dace import from unrelated modules. But this is for @egparedes to answer. (And we could think of the other option as a contribution to productice DaCe.)

[kotsaloscv]

My first impression is that @havogt is right and the best option would be to enhance DaCe with support for registering SDFG convertible functions defined outside of the object. It would improve both the Gt4Py and DaCe codebases and would make this PR much cleaner. Another option, even simpler to implement in the DaCe side, would be to remove the requirement to inherit from SDFGConvertible (which is not even an ABC) and implement it as a typing Protocol using runtime_checkable or a custom typeguard for isinstance() checks.

If we want to merge this PR in the short term before waiting for changes in DaCe, I think it'd be better to add the required DaCe methods and bases conditionally and keep DaCe as an optional requirement, as @edopao and @havogt suggested. For example:

class Program:
    ....

if dace:
    class Program(Program, SDFGConvertible):
        def __sdfg__(self, *args, **kwargs) -> Optional[Any]:
             ....

For now, I would go with the short term approach since we are in the testing/development phase. In the near future, I could create a PR in DaCe to address this topic.

cc: @havogt @edopao

[havogt]

I think we are getting closer. I am still trying to understand how things interact and where stuff belongs. Maybe we could have a chat and you could teach me the interface.