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6.18.3 Generating Topology Files for exch2

Alternate cubed sphere topologies may be created using the Matlab scripts in utils/exch2/matlab-topology-generator. Running the m-file driver.m from the Matlab prompt (there are no parameters to pass) generates exch2 topology files W2_EXCH2_TOPOLOGY.h and w2_e2setup.F in the working directory and displays a figure of the topology via Matlab - figures 6.6, 6.5, and 6.4 are examples of the generated diagrams. The other m-files in the directory are subroutines called from driver.m and should not be run ``bare'' except for development purposes.

The parameters that determine the dimensions and topology of the generated configuration are nr, nb, ng, tnx and tny, and all are assigned early in the script.

The first three determine the height and width of the subdomains and hence the size of the overall domain. Each one determines the number of grid points, and therefore the resolution, along the subdomain sides in a ``great circle'' around each the three spatial axes of the cube. At the time of this writing MITgcm requires these three parameters to be equal, but they provide for future releases to accomodate different resolutions around the axes to allow subdomains with differing resolutions.

The parameters tnx and tny determine the width and height of the tiles into which the subdomains are decomposed, and must evenly divide the integer assigned to nr, nb and ng. The result is a rectangular tiling of the subdomain. Figure 6.4 shows one possible topology for a twenty-four-tile cube, and figure 6.5 shows one for twelve tiles.

Figure 6.4: Plot of a cubed sphere topology with a 32$ \times $192 domain divided into six 32$ \times $32 subdomains, each of which is divided into four tiles of width tnx=16 and height tny=16 for a total of twenty-four tiles. The colored borders of the subdomains represent the parameters nr (red), nb (blue), and ng (green).
\resizebox{4in}{!}{ \includegraphics{part6/s24t_16x16.ps} }

Figure 6.5: Plot of a cubed sphere topology with a 32$ \times $192 domain divided into six 32$ \times $32 subdomains of two tiles each (tnx=16, tny=32).
\resizebox{4in}{!}{ \includegraphics{part6/s12t_16x32.ps} }

Figure 6.6: Plot of a cubed sphere topology with a 32$ \times $192 domain divided into six 32$ \times $32 subdomains with one tile each (tnx=32, tny=32). This is the default configuration.
\resizebox{4in}{!}{ \includegraphics{part6/s6t_32x32.ps} }

Tiles can be selected from the topology to be omitted from being allocated memory and processors. This tuning is useful in ocean modeling for omitting tiles that fall entirely on land. The tiles omitted are specified in the file blanklist.txt by their tile number in the topology, separated by a newline.

next up previous contents
Next: 6.18.4 exch2, SIZE.h, and Up: 6.18 exch2: Extended Cubed Previous: 6.18.2 Invoking exch2   Contents
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