[MITgcm-support] Re: [MITgcm-cvs] MITgcm/model/src CVS Commit

[Jean-Michel Campin]

Hi Martin,

I am still thinking that if there is a problem in mom_calc_visc.F
it should be fixed, and don't see what is wrong with the exch S/R.

I have options for 2 compilers (gfortran & ifort) that make the run
to stop when a division by zero is found.
So I could try to see where the problem is.

Do you know which grid, tiling and parameter file "data" 
cause this problem ? (I guess you are not using useAreaViscLength=T ?)

Thanks,
Jean-Michel


On Thu, Feb 12, 2009 at 06:12:37PM +0100, Martin Losch wrote:
> Hi Jean-Michel,
>
> the problem occurs only on curvilinear grids (that's why  
> ini_curvilinear_grid), and it happens somewhere in mom_common/ 
> mom_calc_visc.F. Basically, L2rdt (and other similar terms) are zero at 
> some points in the overlaps, I think the corners, so i,j=-2, or so and 
> then, when there is a division by L2rdt, then the sxf90 compiler  
> complains/code crashes. The problem goes away with my fix (and we talked 
> about this some time ago, but obviously since then nothing has changed in 
> terms of exchanges) and the actual value of the initialization does not 
> have an impact on the solution at all.
>
> You should be able to reproduce this with any cubed sphere grid  
> (although I only get crashes with sxf90).
>
> Martin
>
> On Feb 12, 2009, at 6:02 PM, Jean-Michel Campin wrote:
>
>> Hi Martin,
>>
>> I am little bit confused:
>> - we do have the proper exchange for dxV & dyU (In fact, I think we
>>  now have the full familly of exch S/R), may be not the adjoint  
>> version.
>> - If there is a division by zero somewhere in the code, I would prefer
>>  to fix it (for all platforms, not only for NEC_SX) rather than
>>  leave with it.
>> Can you point where the problem was ?
>> Thanks,
>> Jean-Michel
>>
>> On Thu, Feb 12, 2009 at 02:51:56AM -0500, Martin Losch wrote:
>>> Update of /u/gcmpack/MITgcm/model/src
>>> In directory forge:/tmp/cvs-serv13873/model/src
>>>
>>> Modified Files:
>>> 	ini_curvilinear_grid.F
>>> Log Message:
>>> check my hack for SX8 compiler, because I keep stumbling over it.
>>> (forgive me, Jean-Michel):
>>> terrible hack to make sure that recip_dxV and recip_dyU are never  
>>> zero,
>>> until we have a proper exchange for them. Most compilers do not seem
>>> to mind divisions by zero in the overlaps, as long as the results are
>>> not used anywhere, but sxf90 does.
>>>
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