Developer guides

These pages explain the implementation choices behind VVMex. Start with the architecture and physics overviews, then open a subsystem guide when changing that area.

Guide	Read it when you need to…
System architecture	Follow startup, MPI/Kokkos ownership, major targets, and repository layout
Physics implementation	Understand the model time-step order and optional physics components
P3 modifications	Compare VVMex microphysics coupling with EAMxx and original Fortran P3
RRTMGP modifications	Understand the single-precision radiation fixes
BP5 output internals	Change the BP5 schema, writer, restart path, or staging behavior
Reproducibility	Diagnose repeatability or CPU/GPU floating-point differences
Continuous integration	Change test tiers, workflows, runners, or branch protection

Build and test orientation

The root CMakeLists.txt builds the vvm executable from application libraries under src/. With -DBUILD_TESTS=ON, CMake registers unit and integration tests from tests/CMakeLists.txt. Optional BP5, physics, and multirank tiers are selected at configure time.

For a practical build command, use the Quick start. For workflow and runner details, use the CI guide.