[MITgcm-devel] big improvement with SEAICE_CGRID

[Martin Losch]

Hi Jean-Michel,

thanks for the changes in pkg/seaice, this renaming in advect/diffus  
was long overdue, but I never use (nor look at) these routines anymore.

I learned this:
"Whenever a field is exchanged, put it into a (at least local) common  
block."
Is this a new programming rule for the MITgcm (or even more generally)  
in order not to break MPI+MTH?

If so, what about fld3d in ADVECT.F?

Martin

On May 19, 2009, at 4:49 PM, Jean-Michel Campin wrote:

> 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
>>> _______________________________________________
>>> MITgcm-devel mailing list
>>> MITgcm-devel at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-devel
>>
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