[MITgcm-devel] problem in seaice_lsr with cubed sphere

[Martin Losch]

Hi Jean-Michel,

yesterday I implemented the option to compute the LSR solution on overlapping tiles, i.e. a restricted additive schwarz (RAS) method. imin/imax can be 1-SEAICE_OLx/sNx+SEAICE_OLx etc. This works fine for SEAICE_OLx <= OLx-2 on simple domains, but for cubed sphere experiments, I need to set SEAICE_OLx=OLx-3 for this to work. SEAICE_OLx = OLx-2 (=2) I get NaN in global_ocean.cs32x15.seaice (and others that use LSR), in the second linear iteration of the solver. 
The reason seems to be BU=0 in some of the corner halos (34,18,2,1), and this is because recip_raw(34,18,2,1) seems to be zero.

Can you reproduce this problem (set SEAICE_OLx=2, and SEAICE_OLy = 2 in global_ocean.cs32x15/input.seaice/data.seaice and run ./testreport -t global_ocean.cs32x15)?
Can we find a decent way to fix that? Initialise recip_raw=1 always? or do I have to check my BU/BV and reset them if they are zero?

Martin