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The JULES model can be run in serial or in parallel on a computer platform [by which I mean a UNIX/Linux computer - see my UNIX Basics doc if not familiar with UNIX/Linux - for example one of the compute machines listed below].
My tutorial JULES From Scratch is wholly focused on serial runs only. In the world of parallel programming, there are three (currently) ways to do it: (1) Multi-node (= using MPI) (2) Multi-thread (= using OMP) (3) Multi-node and multi-thread at the same time (see Fig. 1 right) (n.b. interrupt-driven multi-tasking is not a form of parallelisation). From the user point of view, many things change moving from serial to parallel. Serial running is available on every platform, but not all platforms support parallel, so I've created a quick checklist here to go through to make sure that moving to parallel is possible for you on the platform you are using. CHECKLIST: (i) You will need appropriate NetCDF libraries for a parallel run. See here. (ii) You will need your driving data and ancillary file location(s) and output location(s) to be on partitions that support parallel reading & writing (e.g. on JASMIN the scratch partitions scratch-nopw and scratch-pw3 are named according to whether they will support parallel writing (pw) or not (nopw)). |
Figure 1: Schematic representation of a hierarchical mixed mode progamming model for a two-dimensional grid array.
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Compute resource terminology:
NODE = Server/computer
CORE = Processor (most servers have 64 or 128 cores). Not the same as a CPU: a CPU usually has multiple cores.
CLUSTER = A collection of interconnected nodes
MPI = Message Passing Interface, the standard for producing message passing libraries (message passing = exchanging information between processes, frequently on separate nodes).
MPICH = A common MPI implementation built on the chameleon communications layer
Compute machines available* for running a model like JULES:
JASMIN = A UK superdata cluster for environmental science research https://jasmin.ac.uk/
- I personally use JASMIN a lot for JULES runs: see my page JULES on JASMIN.
ARCHER2 = A UK national supercomputing service https://www.archer2.ac.uk/
MONSOON2 = UK Met Office & NERC joint supercomputer system https://www.metoffice.gov.uk/research/approach/collaboration/jwcrp/monsoon-hpc
* n.b. not necessarily restricted to use by UK nationals: please check the platform's terms & conditions.
NODE = Server/computer
CORE = Processor (most servers have 64 or 128 cores). Not the same as a CPU: a CPU usually has multiple cores.
CLUSTER = A collection of interconnected nodes
MPI = Message Passing Interface, the standard for producing message passing libraries (message passing = exchanging information between processes, frequently on separate nodes).
MPICH = A common MPI implementation built on the chameleon communications layer
Compute machines available* for running a model like JULES:
JASMIN = A UK superdata cluster for environmental science research https://jasmin.ac.uk/
- I personally use JASMIN a lot for JULES runs: see my page JULES on JASMIN.
ARCHER2 = A UK national supercomputing service https://www.archer2.ac.uk/
MONSOON2 = UK Met Office & NERC joint supercomputer system https://www.metoffice.gov.uk/research/approach/collaboration/jwcrp/monsoon-hpc
* n.b. not necessarily restricted to use by UK nationals: please check the platform's terms & conditions.