[MITgcm-devel] big improvement with SEAICE_CGRID

[Jean-Michel Campin]

Hi Martin,

Thanks for your comments.
I switched off all the SEAICEadvXXX (SEAICEadvHeff, SEAICEadvArea
+ the other, to be on the safe side), and it's working fine.
My guess is that there are EXCH applied to non-shared array,
which works fine in multi-threaded without MPI, but does not
work with both. And as you remind me, the SEAICE_CGRID has 
some effect on what/where things are exchanged.

Just one coment:
I have #undef SEAICE_ALLOW_DYNAMICS and SEAICEuseDYNAMICS=.FALSE.,
but SEAICE_DYNSOLVER is still called from seaice_model, and
is doing something. May be we could check what is really needed
when SEAICEuseDYNAMICS=F and skip some part of code in this case.

Cheers,
Jean-Michel

On Tue, May 19, 2009 at 09:09:38AM +0200, Martin Losch wrote:
> I am glad to hear that the c-grid seaice is soo much better (o:
>
> How do I reproduce this problem? What options for testreport and what  
> machine configuration, number of cpus, which compiler?
>
> The SEAICE_CGRID option replaces the call to dynsolver (and then lsr and 
> ostres) with seaice_dynsolver (and seaice_lsr or seaice_evp, and then 
> seaice_ocean_stress, further there are new subroutines  
> seaice_calc_strainrates, seaice_calc_viscosities, which are not called  
> for the the B-grid code). The forcing is treated differently  
> (seaice_get_dynforcing). Then there is an averaging of ice velocities  
> from B-grid to C-grid points in seaice_advdiff and an additional  
> exchange, which is of course removed with SEAICE_CGRID. Since in the  
> offline experiment, the solver is not called, I would start looking  
> there (seaice_advdiff).
>
> Currently, I cannot even update the code because of CVS-problems, so I  
> can't try to reproduce this problem.
>
> Martin
>
>
> On May 19, 2009, at 6:09 AM, Jean-Michel Campin wrote:
>
>> Hi,
>>
>> I think I have to report on this huge improvement (10^60)
>> I noticed when switching on SEAICE_CGRID:
>>
>> It started with those MPI+MTH tests, all 4 lab_sea tests
>> get stuck somewhere, and today I noticed that
>> offline_exf_seaice.seaicetd has the same problem (whereas
>> the standard offline_exf_seaice, which does not use any seaice,
>> is passing well the MPI+MTH test).
>> The option file SEAICE_OPTIONS.h from offline_exf_seaice/code
>> is out of date, so I started to switch to an up-to date version,
>> keeping most options just #undef. The only one I turned on
>> (compared to the old version) is "SEAICE_CGRID".
>> And guess what ?
>> The results improve by 60 order of magnitude !
>> Before, HEFF was reaching ~10^120 after 1 iteration (and stopping
>> before the end of the 2nd one), but now it's only 10^61, and can
>> even go through the 2nd iteration, with only a moderate increase
>> (in log scale) at the end of the 2nd iter (10^62).
>>
>> More seriously, an advise on where to start to look at ?
>> (works well with MPI alone, MTH alone, but not with both)
>>
>> Thanks,
>> Jean-Michel
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