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Minimum decomposed computational patch size

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.


In v4.0, in share/module_check_a_mundo.f90, a check has been added that prevents REAL and WRF from running if a patch is too small (< 10 cells in either dimension). This prevents for a modest set of grids (below) from running if the number of procs is below about 300 (both grids 1 and 2 fail the check). In this case, we might want to suffer some over decomposition on the outer 2 grids in order to achieve better performance on the innermost grid. Can (or should) this check be relaxed?

e_we = 181, 199, 259
e_sn = 181, 199, 325

I believe the check should be the other way around, so that you cannot use too many processors for a small grid. So for the first domain, if you used 36 processors, the decomposition would be 6x6, and 181/6 is ~30 grid cells, which would be perfectly fine, as it's greater than 10.