Changeset 11551 for NEMO/trunk/doc/latex/NEMO/subfiles/chap_LBC.tex
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 20190916T16:53:24+02:00 (5 years ago)
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NEMO/trunk/doc/latex/NEMO/subfiles/chap_LBC.tex
r11543 r11551 341 341 342 342 If the domain decomposition is automatically defined (when \np{jpni} and \np{jpnj} are < 1), the decomposition chosen by the model will minimise the subdomain size (defined as $max_{all domains}(jpi \times jpj)$) and maximize the number of eliminated land subdomains. This means that no other domain decomposition (a set of \np{jpni} and \np{jpnj} values) will use less processes than $(jpni \times jpnj  N_{land})$ and get a smaller subdomain size. 343 In order to specify $N_{mpi}$ properly (minimize $N_{useless}$), you must run the model once with \np{ln\_list} activated. In this case, the model will start the initialisation phase, print the list of optimum decompositions ($N_{mpi}$, \np{jpni} and \np{jpnj}) in \texttt{ocean.output} and directly abort. The maximum value of $N_{mpi}$ tested in this list is given by $max(N_{MPI\_tasks}, \np{jpni} \times \np{jpnj})$. For example, run the model on 40 nodes with ln\_list activated and $\np{jpni} = 10000$ and $\np{jpnj}= 1$, will print the list of optimum domains decomposition from 1 to about 10000.343 In order to specify $N_{mpi}$ properly (minimize $N_{useless}$), you must run the model once with \np{ln\_list} activated. In this case, the model will start the initialisation phase, print the list of optimum decompositions ($N_{mpi}$, \np{jpni} and \np{jpnj}) in \texttt{ocean.output} and directly abort. The maximum value of $N_{mpi}$ tested in this list is given by $max(N_{MPI\_tasks}, jpni \times jpnj)$. For example, run the model on 40 nodes with ln\_list activated and $jpni = 10000$ and $jpnj = 1$, will print the list of optimum domains decomposition from 1 to about 10000. 344 344 345 345 Processors are numbered from 0 to $N_{mpi}  1$. Subdomains containning some ocean points are numbered first from 0 to $jpni * jpnj  N_{land} 1$. The remaining $N_{useless}$ land subdomains are numbered next, which means that, for a given (\np{jpni}, \np{jpnj}), the numbers attributed to he ocean subdomains do not vary with $N_{useless}$.
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