[MITgcm-devel] problem in seaice_lsr with cubed sphere

[Martin Losch]

Hi Jean-Michel,

thanks for this trick: I inserted this routine after the exch_uv_xy_rl at the end of the linear iteration and this fixes the problem.

Now, do we need to make a _RL version that can also handle 4D arrays (with bi,bj indices) or can we just call it like this:

call fill_cs_corner_uv_rs(.true.,uice(:,:,bi,bj),vice(:,:,bi,bj),bi,bj,myThid)

I have the feeling that this only works for me because nSy = 1, so I would actually make a routine that takes 4D arrays (but that wouldn’t be consistent with the _RS version, what’s best in your opinion?

Martin

On Dec 3, 2014, at 2:26 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:

> Hi Martin,
> 
> Did you try something like one or more calls to S/R FILL_CS_CORNER_UV
> (we currently only have the _RS version but would not be difficult
> to make an _RL ; and as long as _RS = real*8, you can certainly give 
> it a try just calling the _RS version).
> 
> Cheers,
> Jean-Michel
> 
> On Wed, Dec 03, 2014 at 01:47:33PM +0100, Martin Losch wrote:
>> Hi again,
>> 
>> after playing a little, it seems there are more problems than just the zero recip_raw/ras, so it may be easier to just include a resetting of zero BU/BV at the end of the routine (although this may cover up unrecognized problems).
>> 
>> Since this all of this is sufficiently fragile, I’d like to add the new capabilitiies: RAS and strong implicit coupling in one of the test experiments. How about global_ocean.cs32x15/input.seaice ?
>> 
>> Martin
>> 
>> On Dec 2, 2014, at 11:55 AM, Martin Losch <Martin.Losch at awi.de> wrote:
>> 
>>> 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
>>> 
>>> 
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>> 
>> 
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