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Question
How many subdomains and threads should I use launching a MIKE 21/3 FM simulation?

Answer
Launching a simulation from within the MIKE 21 Flow Model FM, MIKE 3 Flow Model FM, MIKE 21/3 Coupled Model FM, MIKE 21 Spectral Waves FM or MIKE 3 Wave FM editors makes the “Launch Settings” dialogue appear

On the “Parallelization” tab in this dialogue the user can specify which parallelization technique to use for the simulation – see example in Fig. 1.
 

 Fig. 1 - The ‘Launch Settings’ dialogue where parallelization technique is specified 

The number of subdomains specifies the number of domains to decompose the model domain into. Generally, this number should not exceed the number of CPU cores available on the machine. When utilizing GPUs, this number should reflect the number of GPUs to use for the simulation. On rare occasions, it might be beneficial, from a performance perspective, to use more subdomains than GPUs.
 
The number of threads per subdomain specifies the number of OpenMP threads to use for each subdomain during the simulation. As a rule of thumb, this number times the number of subdomains should be less than or (preferably) equal to the total number of CPU cores available on the machine.

Note: The expiry date for the GPU option in the license file follows the SMA expiry date.