112 | | On `Domain Decomposition -> Atmosphere`, the number of processes used by the UM can be set via `Atmosphere: Processes East-West` and `Atmosphere: Processes North-South`; additional processes for the IO Server may be requested using `IO Server Processes`. Finally, `OpenMP threads for the atmosphere` sets the number of threads for each process; multiplying this by the number of processes gives the number of compute tasks. Using the default values for these parameters, the number of tasks used by the UM is `(32 * 18 + 0) * 2 = 1152`. Dividing by the number of cores per node (in this case `36`) and rounding up (because different executables cannot run on the same node) gives `32` compute nodes used by the atmosphere. |
| 112 | The suite is currently set up in `suite conf -> Domain Decomposition` to use 36 nodes (see [#Calculationofnodecount below] for more details on how this is calculated). An alternative setup uses 19 nodes. Parameter settings for both setups are: |
| 113 | |
| 114 | ||=''Parameter''=||=''36 node suite''=||=''19 node suite''=|| |
| 115 | ||=Atmosphere: Processes East-West=||=32=||=32=|| |
| 116 | ||=Atmosphere: Processes North-South=||=18=||=18=|| |
| 117 | ||=IO Server Processes=||=0=||=0=|| |
| 118 | ||=OpenMP threads for the atmosphere=||=2=||=1=|| |
| 119 | ||=NEMO: Number of processes East-West=||=12=||=9=|| |
| 120 | ||=NEMO: Number of processes North-South=||=9=||=8=|| |
| 121 | ||=NEMO: Number of processes in XIOS server=||=6=||=6=|| |
| 122 | ||=OpenMP threads for the ocean=||=1=||=1=|| |
| 123 | |
| 124 | Note that the ocean must be rebuilt (by setting `suite conf -> Build and Run -> Build Ocean` to `true`) whenever the NEMO parameters in the table are changed during a run. |
| 125 | |
| 126 | Setting these parameters to other values may require load balancing to ensure that HPC resources are being used in the most efficient fashion. |
| 127 | |
| 128 | === Calculation of node count |
| 129 | |
| 130 | On `Domain Decomposition -> Atmosphere`, the number of processes used by the UM can be set via `Atmosphere: Processes East-West` and `Atmosphere: Processes North-South`; additional processes for the IO Server may be requested using `IO Server Processes`. Finally, `OpenMP threads for the atmosphere` sets the number of threads for each process; multiplying this by the number of processes gives the number of compute tasks. |
| 131 | |
| 132 | Using the parameter values for the ''36 node suite'', the number of tasks used by the UM is `(32 * 18 + 0) * 2 = 1152`. Dividing by the number of cores per node (in this case `36`) and rounding up (because different executables cannot run on the same node) gives `32` compute nodes used by the atmosphere. |