Add CI workflows and implement unit tests for MPAS dynamical core

[kuanchihwang]

Tag name (required for release branches):

None

Originator(s):

kuanchihwang

Descriptions (include the issue title, and the keyword ['closes', 'fixes', 'resolves'] followed by the issue number):

This PR introduces continuous integration (CI) workflows and implements unit tests for MPAS dynamical core. Additionally, pFUnit files (*.pf) are now correctly rendered as Fortran source code on GitHub.

Beyond verifying correctness and robustness, the unit tests also report the numerical accuracy of each computational procedure in terms of units in the last place (ULP) away from the exact answers. For example, below is the output for equation of state:

2:  Start: <test_dyn_procedures_suite.test_equation_of_state_family_by_typical_values>
2: .
2: Error statistics (N = 31512303):
2:  63.81% of sample values (20107401) have accuracy of 0 <= ULP < 1.
2:  34.31% of sample values (10810918) have accuracy of 1 <= ULP < 2.
2:   1.88% of sample values (593637) have accuracy of 2 <= ULP < 3.
2:   0.00% of sample values (347) have accuracy of 3 <= ULP < 4.
2:    end: <test_dyn_procedures_suite.test_equation_of_state_family_by_typical_values>

Whenever changes are made in the path of MPAS dynamical core (src/dynamics/mpas/*), the CI workflows automatically build and run the unit tests with various versions of GCC. Test results are collected as artifacts and retained for 7 days for reference.

Describe any changes made to the build system:

None

Describe any changes made to the namelist:

None

List any changes to the defaults for the input datasets (e.g., boundary datasets):

None

List all files eliminated and why:

None

List all files added and what they do:

A       .gitattributes
  * Make GitHub Linguist recognize `*.pf` files as Fortran source code
A       .github/workflows/mpas_dynamical_core_ci.yml
  * Add CI workflow for MPAS dynamical core
A       src/dynamics/mpas/CMakeLists.txt
A       src/dynamics/mpas/tests/unit/CMakeLists.txt
A       src/dynamics/mpas/tests/unit/test_dyn_mpas_procedures.pf
A       src/dynamics/mpas/tests/unit/test_dyn_procedures.pf
  * Implement unit tests for MPAS dynamical core

List all existing files that have been modified, and describe the changes:

M       .github/workflows/fortran_unit_tests.yml
  * Exclude `main` branch from CAM-SIMA CI
  * Pin Ubuntu runner image version for better CI stability
  * Give CI job more descriptive name
  * Add pFUnit caching to CAM-SIMA CI
  * Refactor PIO build steps
  * Use `actions/checkout@v5` for all `git checkout` operations
  * Refactor unit testing steps
  * Simplify dependency installation
M       src/dynamics/mpas/driver/dyn_mpas_procedures.F90
  * Add support for comparing NaN and Inf with `almost_equal`
M       src/dynamics/mpas/dyn_comp_impl.F90
  * Use `almost_equal` for checking topography data
  * Use `qv_of_sh` for converting specific humidity to water vapor mixing ratio
M       src/dynamics/mpas/dyn_coupling_impl.F90
  * Use `exner_function` for improved readability in dynamics-physics coupling
  * Sort `use` statements
M       src/dynamics/mpas/dyn_procedures.F90
  * New interface for `exner_function`
  * Explicitly specify integers to be `int32` in `sec_to_hour_min_sec`

Regression tests:

FAIL SMS_Ln9.ne3pg3_ne3pg3_mg37.FKESSLER.derecho_intel.cam-outfrq_se_cslam_multitape NLCOMP

Except for the known failing test above, all the other tests pass with respect to the last baseline, sima0_08_002.

[kuanchihwang]

To reviewers, if you are interested in the CI workflow logs, look for "MPAS Dynamical Core CI" in the "Checks" tab of this PR.

[nusbaume]

Thanks for bringing in all of these unit tests @kuanchihwang! I mostly just had a few comment-related requests, as well as a request that would slightly expand the scope of this PR (so feel free to say no if it is too burdensome).

[nusbaume]

Thanks for bringing in my requests @kuanchihwang! This PR looks good to me now.