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Performance for different grid dimensions
Using a fixed number of processors we investigate how the shape of the grid
affects the performance. We concentrate on 128 and 256 processors with two
results from a 512 processor run. All runs are carried out using the PGI
compiler suite. The results of this experiment are shown in figure
4.
Figure 4:
Performance of NEMO on 128, 256 and 512 processors plotted against
the number of grid cells in the 
direction, 
|
|
Figure 4 suggests that for a fixed number of
processors the ideal grid dimensions are square i.e. where
jpni=jpnj. If the number of processors is such that it is not
possible to have jpni=jpnj (i.e. the number of processors is not a
square of an integer) then the results suggest that the values of
jpni and jpnj should be as closer to each other as
possible with the value of jpni chosen such that
jpni < jpnj.
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