Add the Long 1974 piecewise collision kernel

[ekdejong]

• Includes additional functionality in pair methods to support comparison and "where"
• Adds a new option for collision kernel dynamics
• Includes a new unit test in collision kernels

[slayoo]

thank you @ekdejong !!!
CC-ing @yoctoyotta1024, @jbarr444 and @emmacware

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.93%. Comparing base (2b58ab4) to head (9a4c747).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1785      +/-   ##
==========================================
+ Coverage   86.85%   86.93%   +0.08%     
==========================================
  Files         415      416       +1     
  Lines       10558    10625      +67     
==========================================
+ Hits         9170     9237      +67     
  Misses       1388     1388              

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[ekdejong]

@slayoo Can you help me understand the test that is currently failing? I made the linter happy, but it seems like black is still acting. Do I just need to run Black locally?

[slayoo]

@slayoo Can you help me understand the test that is currently failing? I made the linter happy, but it seems like black is still acting. Do I just need to run Black locally?

black is executed automatically via a pre-commit hook after doing pre-commit install. Following it, a git commit ... command will trigger black, which will alter the files, and will stop the commit. Here, you can do git diff to make sure all of the automatic changes to the code are OK, following which repeating the same git commit ... command should work.

(this is mentioned in the README: https://github.com/open-atmos/PySDM/blob/main/README.md?plain=1#L131-L135, but any feedback on how to better explain the workflow warmly welcome!)

[ekdejong]

Thank you, @slayoo ! It's been some time since I contributed, clearly...

(this is mentioned in the README: https://github.com/open-atmos/PySDM/blob/main/README.md?plain=1#L131-L135, but any feedback on how to better explain the workflow warmly welcome!)

And speaking of which, thank you for bringing to my attention that the README has some valuable information on contributing! My bad for overlooking this.

[slayoo]

(let me also clarify that from all the above comments, adding an example notebook reproducing a figure from the paper is by far my key suggestion here, and I'm happy to help with equipping it later with a smoke test executing the notebook code)

[slayoo]

(let me also clarify that from all the above comments, adding an example notebook reproducing a figure from the paper is by far my key suggestion here, and I'm happy to help with equipping it later with a smoke test executing the notebook code)

Thanks @slayoo! I've added a notebook to replicate some of the DSDs in the Long paper. I think an appropriate smoke test could be to confirm the size of the mode in the DSD, and/or to confirm a comparison between the mean size predicted using the Long kernel versus Golovin kernel.

Thank you @ekdejong !

BTW, fun fact (thanks to @emmacware): Golovin's solution was actually given a bit earlier in the same journal by Safranov, which is why it is called Safranov kernel/solution in astrophysical literature: Safranov, V. S. (1962). "A particular solution of the coagulation equation" [in Russian: "Частный случай решения уравнения коагуляции"]. Bull. Acad. Sci. SSSR Geophys. Ser., 147 (1), 64—67. https://mathnet.ru/dan27172

[ekdejong]

@slayoo The current failing test appears related to condensation, not the kernels. Would you mind giving this PR another look (or suggesting another reviewer) so we can work toward merging?

[slayoo]

@slayoo The current failing test appears related to condensation, not the kernels. Would you mind giving this PR another look (or suggesting another reviewer) so we can work toward merging?

hi @ekdejong, the job name is misleading here, but the failure is related to the changes here:

=========================== short test summary info ============================
FAILED tests/examples_tests/test_tests_completeness.py::test_all_cases_in_testsuites - AssertionError: assert {'/home/runne..._ARG.py', ...} == {'/home/runne..._ARG.py', ...}
  
  Extra items in the right set:
  '/home/runner/work/PySDM/PySDM/examples/PySDM_examples/Long_1974/simulation.py'
  '/home/runner/work/PySDM/PySDM/examples/PySDM_examples/Long_1974/fig10_11_13_14.ipynb'
  '/home/runner/work/PySDM/PySDM/examples/PySDM_examples/Long_1974/settings.py'

fix on the way...

[slayoo]

for the record, the "failure" can be reproduced locally with:

$ pytest tests/examples_tests/test_tests_completeness.py 
============================= test session starts ==============================
platform linux -- Python 3.13.5, pytest-9.0.2, pluggy-1.6.0
rootdir: /home/user/devel/PySDM
configfile: pyproject.toml
plugins: anyio-4.12.1
collected 3 items                                                              

tests/examples_tests/test_tests_completeness.py F..                      [100%]

=================================== FAILURES ===================================
_________________________ test_all_cases_in_testsuites _________________________

    def test_all_cases_in_testsuites():
        """raise error, e.g., if a newly added example is not within TEST_SUITES dict"""
        tmp = findfiles(
            pathlib.Path(__file__)
            .parent.parent.parent.absolute()
            .joinpath("examples")
            .joinpath("PySDM_examples"),
            r".*\.(py|ipynb)$",
        )
        all_files = list(
            filter(
                lambda x: pathlib.Path(x).name != "__init__.py",
                tmp,
            )
        )
    
        selected_paths_set = set()
        for suite_name in TEST_SUITES:
            selected_paths_set.update(
                map(str, get_selected_test_paths(suite_name, all_files))
            )
    
        assert len(all_files) > 0
>       assert selected_paths_set == set(all_files)
E       AssertionError: assert {'/home/user/..._ARG.py', ...} == {'/home/user/..._ARG.py', ...}
E         
E         Extra items in the right set:
E         '/home/user/devel/PySDM/examples/PySDM_examples/Long_1974/simulation.py'
E         '/home/user/devel/PySDM/examples/PySDM_examples/Long_1974/settings.py'
E         '/home/user/devel/PySDM/examples/PySDM_examples/Long_1974/fig10_11_13_14.ipynb'
E         Use -v to get more diff

tests/examples_tests/test_tests_completeness.py:32: AssertionError
=========================== short test summary info ============================
FAILED tests/examples_tests/test_tests_completeness.py::test_all_cases_in_testsuites - AssertionError: assert {'/home/user/..._ARG.py', ...} == {'/home/user/..._A...
========================= 1 failed, 2 passed in 0.16s ==========================