Painless shell scripts to set up a ninja build of MOM6 on NCI with Intel compilers. As prerequisites, I recommend you have the latest intel-compiler module loaded, netcdf, and a modern version of OpenMPI (4.0.x).

1. Clone https://github.com/NOAA-GFDL/MOM6-examples to your home directory
2. From within the MOM6-examples directory run git submodule update --init --recursive to fetch the rest of the components
3. (Optional) In MOM6-examples/src/MOM6 and MOM6-examples/src/FMS, run git checkout dev/gfdl and git checkout 2021.01, respectively to track the most recent set of compatible versions
4. Clone this repository (preferably on /scratch, as the directories will fill up with object files and executables)
5. Go inside mom6-ninja-nci directory and edit ./gen_build.sh to point the srcdir variable to the src directory of MOM6-examples (e.g. $HOME/MOM6-examples/src)
6. Run ./gen_build.sh to generate the overall config file for compiler flags (you may edit the config.ninja file afterwards to change these)
7. Make sure you have the ninja executable somewhere in your PATH

The shared subdirectory is to build the FMS library against which MOM6 is linked.

1. In shared, run ./gen_build.sh to generate the build script
2. (Optional) Check build.ninja seems sensibly populated
3. Build it! Run ninja

The ocean_only_symmetric subdirectory contains configuration for the ocean only (i.e. no sea ice or other coupling), symmetric C-grid, dynamic memory version of the model. Build steps are identical to FMS:

1. In ocean_only_symmetric, run ./gen_build.sh to generate the build script
2. (Optional) Check build.ninja seems sensibly populated
3. Build it! Run ninja

You now have a MOM6 executable.

Most of the time, you will only be tweaking MOM6 source, so only MOM6 itself needs to be rebuilt. In many cases, changes to the source won't change the dependency order, so you can just re-run ninja, which will recompile only what is necessary, as any build system would. If the dependency order is changed (usually from added use statements here and there), re-run ./gen_build.sh.