Hall 1980 collision efficiencies

[jbarr444]

Hi @slayoo,

How would I go about modifying collision efficiencies of the Geometric (or maybe Hydrodynamic) kernel? It seems (correct me if I'm wrong) like you can pass one number for all pairs of sizes, but I'm interested in using Hall's 1980 table. Is this possible?

Thanks,
Jason

[slayoo]

Hi @jbarr444,

The Geometric kernel ctor indeed allows to alter the collision efficiency (one for all sizes).

The Hydrodynamic kernel ctor has no parameters as it was written to reflect one particular parameterisation from the Berry 1967 paper.

Hall's table is not implemented yet, contribution welcome!

S.

[slayoo]

Both backends use just-in-time compilation, so a significant speedup is expected (x100 not surprising, all depends on the code in question). Please do submit a PR - it facilitates discussion and also provides numerous automatic checks. Thanks!

[jbarr444]

Embarrassing but how do you submit a PR? Should I create a new fork? I don't want to break anything. I am very inexperienced in actual software development :)

[slayoo]

Happy to help! You indeed need a fork (in the GitHub cloud), a local clone of this fork, and a new branch in that clone (which will track a branch on the fork). The steps would be:

• create a fork by pointing a browser to https://github.com/open-atmos/PySDM/fork,
• generate a public-private key pair on your machine using ssh-keygen (see https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent)
• register the public key in GitHub settings (https://docs.github.com/en/authentication/connecting-to-github-with-ssh/adding-a-new-ssh-key-to-your-github-account)
• clone your PySDM form by running locally git clone [email protected]:jbarr444/PySDM.git
• change directory to PySDM with cd PySDM
• set up pre-commit hooks with pip install pre-commit and pre-commit install
• create and checkout to a new branch with git checkout -b hall_efficiencies
• add your code changes, new files, etc
• commit the changes (see https://git-scm.com/book/en/v2/Git-Basics-Recording-Changes-to-the-Repository), noting that the pre-commit hooks will likely make the first correct commit command fail due to changes being introduced by the pre-commit hooks (things like removing redundant spaces in the code, enforcing a particular style of parentheses, quotes, indentation, etc), just rerun the same commit command after that and it will pass
• push the changes to your fork with git push --set-upstream origin hall_efficiencies
• create a PR at https://github.com/open-atmos/PySDM/pulls/new (see also https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests)

Upon creation of the PR, maintainers of the project watching the repo will receive notification to approve execution on "Continuous Integration" tests in the cloud. This will trigger a set of checks that you can track on the new PR's page. The checks include things like:

• code style checks with pylint (which you can run locally)
• code-coverage level analysis (which will only pass if a new unit test in PySDM/tests/unit_tests is present and executes all the newly introduced code)
  We maintain some open-atmos-specific Python dev hints here: https://github.com/open-atmos/python-dev-hints/wiki

HTH

[jbarr444]

Thanks so much!! The PR has been created, with just a single new file 'hall.py' sitting with the other collision kernels. Let me know anything else I can do regarding this.

[slayoo]

Thank you! I'll post comments in the PR.