Pybind support

[larryliu0820]

After enabling pybind we should be able to migrate a lot more internal tests to OSS. Currently the pybind repo is checked in third-party/ but need some wiring to make it work for python_cpp_extension BUCK macros.

[larryliu0820]

Existing attempt: https://github.com/pytorch/executorch/tree/pybind

[mergennachin]

Hi @larryliu0820

Is (#332) sufficient ?

Can you mention about what's the status, how people can use portable_lib pybindings, add documentation (if necessary) and close this task?

[larryliu0820]

#332 enabled building pybind shared library and used it in end2end test. This is a good progress but we need some UX work:

1. Package the pybind shared library along into pip install. This exposes python modules under executorch.extension.pybindings for users to use.
2. Hook this up with selective build so we can do selective build based on .pte model files.

[mergennachin]

Hook this up with selective build so we can do selective build based on .pte model files.

Was there an actual need from developers? Why is this important?

As far as I can tell, pybind is mostly used for testing as well as fast iteration and experimentation.

I don't expect developers to use pybind for an actual on-device deployment, and hence, selective build for pybind doesn't seem necessary. It seems enough to just link against all portable operators.

[larryliu0820]

Yeah not saying we are using pybind for actual model development. Pybind exposes a python API to extracts operator information from model and we would want users to use that API. Currently users can only hardcode operator names in OSS.

[mergennachin]

Ah, yes yes. I remember now.

Thanks a lot, this is great progress so far

[swolchok]

@larryliu0820 can we close this? we use pybind, not sure if there's more to this issue

[larryliu0820]

Yeah I think this can be closed.