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Parallelization of GSI IO for fv3-lam #218
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An update: |
A rather complete verification and polishing (removing unused variables and duplicated variables for the same parameters) of the parallel IO for fv3 lam have been finished. In an 3km conus domain cold start test ,the parallel IO for fv3-cam demonstrates significant speeding up and much less maximum resident memory . For details, pls see the attachment. |
The tests includes the use of control variables with hydrometeors when l_use_direct_dbz is true, though no dbz observation is used. Thanks to J. Park @junpark217 OU providing the namelist block and anavinfo file for this test. |
GitHub Issue #218. GSI parallel IO for FV3-LAM
The parallelization of GSI IO for fv3-lam (including reading of fv3-lam ensemble) has been considered at EMC and outside collaborating institutes. Especially, recent fv3-lam forecast model prefer to directly dump data on subdomains in selected layout to speed up the model IO. This needs corresponding treatment on GSI IO part.
This IO issue is complicated because it is in association with the needed conversion between the native model grids and GSI analysis regular grids, which is done in the full domain. To implement a more complicated conversion scheme, which can be done on subdomain, need the efforts, seemingly, beyond current consideration.
However, as GSI deal with the horizontal recursive filter, the parallelization along the vertical levels could cause significant speeding up.
For example, recently @guoqing-noaa realized the parallelization of analysis writing by parallelization in the vertical levels with coding "from scratch" , NOAA-GSL#4. His results show obvious improvement in the writing step.
This issue is demonstrate our efforts to make use of GSI existing interface (based on general_sub2grid_mod.f90) for the parallelization of the horizontal recursive filtering as the basic parallelization frame for FV-LAM IO to incorporate use of the "parallel netcdf" and use of parallel IO subroutine in fms (used by FV3 model IO). We expect such developed coding would provide well wrapped and easier expandable interface for GSI parallelized IO for FV3-LAM.
The design is maybe changed according to discussions/tests among developers.
This issue will demonstrate discussions/comments/suggestions and test results during this developing process.
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