Experimental Apple Silicon (M1) support

[Corwinpro]

PR type: enhancement

Related issue(s)/PRs: Contributes to #1850

Summary

Proposed changes

This PR introduces basic support for Apple Silicon MacOS. This is achieved by pulling tensorflow-macos dependency instead of regular tensorflow at setup time.

This has been tested on an Macbook Pro 2021 M1 Pro, python3.8.

• Update setup.py to dynamically decide on the tensorflow source depending on the platform
• Changes in gpflow/utilities/traversal.py and test_traversal.py come from the common type of errors that 0.999999 != 1.0 and representation of floating point numbers.

What alternatives have you considered?

No alternatives have been considered. Please let me know if there are any.

Minimal working example

python3.8 -m venv gpflow-py38
source gpflow-py38/bin/activate
python -m pip install -e .
python -m pip install -r tests_requirements.txt
make format
make check-all

Known problems

With python3.8 installed via brew, integration tests for notebooks sometimes fail with OSError: too many files open. I think this is a known issue and can be addressed separately.

Fully backwards compatible: yes

PR checklist

• New features: code is well-documented
  • detailed docstrings (API documentation)
  • notebook examples (usage demonstration)
• The bug case / new feature is covered by unit tests
• Code has type annotations
• Build checks
  • I ran the black+isort formatter (make format)
  • I locally tested that the tests pass (make check-all)
• Release management
  • RELEASE.md updated with entry for this change
  • New contributors: I've added myself to CONTRIBUTORS.md

[codecov]

Codecov Report

Merging #1924 (f024024) into develop (5110164) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1924   +/-   ##
========================================
  Coverage    97.96%   97.96%           
========================================
  Files          109      109           
  Lines         6351     6352    +1     
========================================
+ Hits          6222     6223    +1     
  Misses         129      129           

Impacted Files	Coverage Δ
gpflow/utilities/traversal.py	96.52% <100.00%> (+0.02%)	⬆️

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[jesnie]

Thanks for doing this. It's been on our TODO list for a while, but I don't have access to a mac , so I've not been able to do it myself.

[Corwinpro]

It's been on our TODO list for a while, but I don't have access to a mac , so I've not been able to do it myself.

IIUC, github actions will be (or maybe already has) introducing support for arm64 runners. I am not sure if GPflow can use Github actions for free as a FOSS. If it is possible, we can consider adding CI for this platform.

[jesnie]

LGTM

Can you do a pull from develop to get this up-to-date?

[Corwinpro]

FWIW, I don't think there will be support for GH hosted arm64 MacOS runners any time soon. I will keep an eye on that, and add one once those are available.