[MITgcm-support] Zeros in inactive tiles in the regional model

[WU Yue]

Dear MITgcm team,

I’m running a regional model based on LLC1080 grid (the domain of Face 1 shown in Fig.1). The original version uses sNx = 90, sNy = 90 with 320 active tiles (also 320 processors used) for the entire domain, which takes around 6 days to run 2 experimental years. To focus more on a smaller region and for resource-saving, I masked southern part of the domain (new Face 1 in Fig.2) then uses sNx = 90 and sNy = 60 with 317 active tiles. The new version runs around 4 days for 2 years, which seems good to me that reducing grid number per tile to 2/3 of the origional version, the running time should speed by 1/3 in time.

However, I noticed that the output data size remains the same between the old and new versions. It appears to have values in the region with active tiles, but for those in inactive tiles the model keep assigning to zeros (see two Figs). In that sense, the new version only saves in time but doesn’t save the storage.

Does anyone know whether the processors are used to computing active tiles whilst allocating zeros to inactive tiles? Or is the model do the allocation? (or other?) Are these zeros will definitely exist?

Best wishes,
Yue

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