Moving hpx utilities from earth2grid

[nbren12]

Hey @akshaysubr. Just wanted to summarize the plan for integrating the healpixpad and python routines from earth2grid (link).

This is roughly what we discussed the other day.

• Move healpixpad cuda code in cuhpx.
• Move top-level python APIs (earth2grid.healpix -> cuhpx).

Please confirm this plan. I also had some questions about these topics:

Documentation

Earth2grid has sphinx documentation and sphinx gallery examples for HealPIX which are automatically deployed to github pages. Should we move that here?

Linting

Earth2grid has more python code, so it would be nice to use the linting setup from that project, and reformat the existing cuhpx code to comply if there are any linting errors. Is that okay?

Testing

Earth2grid has an existing test suite. the scripts in "tests" dir in cuHPX are not really unit tests, but instead are scripts that were run at some point to test the implementation. To enable pytest, we will need to rename these files to avoid pytest auto-discovering them and running them. In the long run, it would be nice to turn these into unit tests. It probably isn't that hard, and just requires wrapping in a function named def test_.

earth2grid is tested w/ CPUs on github actions, and then occasionally I manually test in the course of development on my GPU workstation. I don't think we need to worry about GPU testing in CI at the moment.

[akshaysubr]

@nbren12 I largely agree with the plan outlined here. @xiaopoc is working on a couple of items right now that might weave in with this plan:

1. Converting the build system for all the C++/CUDA bits to using CMake. I would suggest that we add in healpixpad once this CMake build system is ready to make it easier to manage.
2. Converting all the scripts in the tests directory to actual pytest unit tests. We don't need to wait for this, but should plan for the other pytest changes to play well with these new tests. This can be done with some simple pytest marks like this.

Regarding linting, the python code in cuHPX already uses black and ruff. The only additional item to match earth2grid would be mypy right? We should add that, but would need to type annotate all the existing code and fix any issues that come up.

Docs: Yes, sphinx docs deployed to github pages sounds good. We can move the earth2grid docs here.

[nbren12]

Sounds good. If we want a head start we can start moving some of the pure python deps over, and then healpixpad and the healpix C code.

The only additional item to match earth2grid would be mypy right?

different versions of ruff/black are sometimes not compatible. For example, I've noticed more recent ruff versions rejecting or auto formatting code that ruff==0.6.9 was compatible with.

[nbren12]

We should add that, but would need to type annotate all the existing code and fix any issues that come up.

mypy doesn't require annotating the whole code base. It can be added incrementally.