[MITgcm-devel] exf: u/v-wind interpolation and cubed sphere

[Martin Losch]

Hi again,

to follow up on this:

I commented out the lines that reset the variable "offset=2" in the  
case when yC is is within dyC of the North Pole, so that offset=0  
always (effectively undoing the latest changes to this file and I  
don't get these complaints by exf_check_range.

I have to admit that I don't understand how this offset-thing works,  
but why is the offset 2, when the wind is rotated near the pole.  
What's happening is that the wind at (i,j) is replaced by the wind at  
(i-offset,j-offset) which in at least one case means, that all the  
information about wind and direction is taken from across the pole.  
Is that correct/indended?

Martin

On Jun 22, 2006, at 11:28 AM, Martin Losch wrote:

> Hi Dimitris,
>
> for benchmarking I successfully run the high_res cubed sphere on  
> our XD1 with 27 cpus (its the ss216t_85x85 configuration), with  
> monthly forcing, (the *194_92_12.bin files). We have moved the  
> entire configuration to an IBM p690 and reran the identical  
> experiment and get this:
>> STOP in S/R exf_check_range
>> STOP in S/R exf_check_range
>> ERROR: 0032-184 MPI was not finalized  in routine unknown, task 10
>> ERROR: 0032-184 MPI was not finalized  in routine unknown, task 11
> We didn't save the output in STDOUT.0021 and STDOUT.0023, but  
> appearently the u/vwinds are wrong (order 10e11) at i=85,j=1 for  
> one tile (I think it was tile 96), and consequently wrong at  
> i=85,j=86 for another tile because of exchanges, also at i=0,j=1  
> and i=1,j=1 at different tiles, and this is reproducible (on the  
> p690 in Hannover). Task 10 owns tiles 81-88 task 11 tiles 89-96; I  
> cannot be sure, but I suspect that the grid points that cause the  
> problem are the four points around the north pole?
>
> [BTW, should i change exf_check_range, so that the STOP command is  
> executed *after* the bi,bj-i,j-loops have finished? That way we  
> would get the numbers of more than one grid point before the system  
> stops. Works nicely for me.
>
> When we do not read uwind/vwind (that is, when these fields are  
> zero), the problem goes away.
>
> I suspect a problem in the interpolation routines, in particular  
> lines such as
>>                     if ( yC(i,j,bi,bj) .gt.
>>      &                  (90-dyC(i,j,bi,bj)*8.9946e-06) )
>>      &                  offset=2
> But that just a wild guess. Do you have any ideas?
>
> Martin
>
> PS: Unfortunately I cannot reprdouce this with a simpler cs-setup.
>
>
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