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When you need to make a new mpas*.part.N file because you changed the number of nodes an MPAS component runs on.  These instructions including adding the file to the repo for others to use.


Step-by-step guide


  1. See if "metis" or "gpmetis" is available on your platform and add it to your path.
    1. On Cray systems, gpmetis is available after `module load metis`.
    2. Do "module spider metis" to find the module to load.
  2. Find the base mpas graph file called "mpas-cice.graph.info.151020" or "mpas-o.graph.info.151031".  These files should be in inputdata/ice/mpas-cice and inputdata/ocn/mpas-ocn respectively.
  3. Run the metis command with the last argument being the number of nodes for the partition.
    1. Example:  "gpmetis mpas-cice.graph.info.151010 120"   will generate a *.part.120 file for mpas-cice.
  4. Place the new file in the correct inputdata subdirectory for the model to find it.


Bonus round: Making better load balanced graph files for MPAS-Seaice

MPAS-Seaice is rather poorly load balanced with standard MPAS graph partitions. This is because sea ice only exists in a very limited part of the domain. A script has been written that can generate somewhat better partitions. Each block is split into 3 non-contiguous sections: One for each polar region and a larger one for the equatorial region. For highly desired changes to this script contact Adrian Turner.

  1. Download the MPAS-Tools repo.
  2. Install the mesh conversion tools (MPAS-Tools/grid_gen/mesh_conversion_tools)
  3. Ensure that your python build includes the netCDF4 library (http://unidata.github.io/netcdf4-python/)
  4. Run the sea ice graph generation script (MPAS-Tools/grid_gen/seaice_grid_tools)

usage: gen_seaice_mesh_partition.py [-h] -m MESHFILENAME -n NPROCS
     [-c MPASCULLERLOCATION] [-o OUTPUTPREFIX]
     [-p] [-g METIS]

Create sea ice grid partition

optional arguments:
     -h, --help show this help message and exit
     -m MESHFILENAME, --mesh MESHFILENAME
          MPAS mesh file
     -n NPROCS, --nprocs NPROCS
          number of processors
     -c MPASCULLERLOCATION, --culler MPASCULLERLOCATION
          location of cell culler
     -o OUTPUTPREFIX, --outprefix OUTPUTPREFIX
          output graph file prefic
     -p, --plotting create diagnostic plotting file of partitions
     -g METIS, --metis METIS
          name of metis utility

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