The first namelist read by the POP model determines how many processors it should use and how to distribute blocks of the domain across processors (see domain decomposition section).
The number of processors used by the model is governed by the nprocs_clinic parameter. The parameter nprocs_tropic determines whether the barotropic solver is run using the same or fewer number of processors; specifying a number larger than the clinic value will result in an error.
| &domain_nml | LANL default |
CCSM4 dipole grids default |
CCSM4 tripole grid default |
Valid values |
Options for controlling domain decomposition |
| nprocs_clinic | auto-filled by CCSM4 POP2 scripts | auto-filled by CCSM4 POP2 scripts | (1,machine maximum) | number of processors to be used for most of the code | |
| nprocs_tropic | auto-filled by CCSM4 POP2 scripts | auto-filled by CCSM4 POP2 scripts | (1,nprocs_clinic) | number of processors to be used for barotropic solver | |
| clinic_distribution_type | 'balanced' | 'balanced' See note below |
''balanced' or 'spacecurve' | 'balanced', 'cartesian', 'spacecurve' | method for distributing blocks across processors for most of the code |
| tropic_distribution_type | 'cartesian' | 'cartesian' | 'cartesian' or 'spacecurve' | 'balanced', 'cartesian', 'spacecurve' | method for distributing blocks across processors barotropic solver |
| ew_boundary_type | 'cyclic' | 'cyclic' | 'cyclic' | 'cyclic', 'closed' | type of boundary in the logical east-west direction for global domain |
| ns_boundary_type | 'cyclic' | 'closed' | 'tripole' | 'cyclic', 'closed','tripole' | type of boundary in the logical north-south direction for global domain |
| / |
The distribution of blocks across processors is determined by the parameters clinic_distribution_type and tropic_distribution_type. Typically, the 'balanced' choice is best for the baroclinic part of the code and 'cartesian' is best for the barotropic solver. The 'spacecurve' choice is sometimes the default for CCSM4 cases using the tripole grid at high resolution on high processor counts.
In order to update ''ghost cells'' and implement proper boundary conditions, some boundary information for the global domain is required. The parameter ew_boundary_type determines the type of boundary for the logical east-west direction (i direction). Acceptable values are currently 'cyclic' and 'closed' for periodic and closed boundaries, respectively. The parameter for the logical north-south direction (j direction) is ns_boundary_type and accepts 'cyclic','closed' and 'tripole', where cyclic and closed have the same meaning as the east-west direction and tripole refers to use of a tripole grid.