[MITgcm-devel] pkg/seaice pseudo time stepping for LSOR

[Martin Losch]

Hi Patrick,

I was afraid of that. Unfortunately it's hard to say what iteration  
count is to be expected, basically I want to play around with this. In  
the recent paper by Lemieux and Tremblay (http://www.agu.org/pubs/crossref/2009/2008JC005017.shtml 
), they find that their model reaches convergence only after 10,500  
iterations. I think that that number is far too much for the generally  
small time steps that we are usually using nowadays, but I cannot  
claim that 100 or 1000 are better guesses.

Can you set a hard limit at say 100, that is only active for adjoint  
computations? The (absolutely feasible) alternative is that I just  
keep my local copy of this parameter. Go for 100.

Martin

On May 27, 2009, at 12:02 AM, Patrick Heimbach wrote:

>
> Hi Martin,
>
> what are max. expected number of pseudo-timesteps.
> As you probably guess, your changes are producing some
> relatively ugly recomp. of seaice_lsr within adseaice_dynsolver.
> For the storing we'll need a hard limit (to be used as
> common block size).
> What's a good number?
>
> Cheers
> -p.
>
> On May 25, 2009, at 5:50 AM, Martin Losch wrote:
>
>> Hi Patrick,
>> I have checked in code to do pseudo time stepping for LSOR.  
>> Basically, the two calls to seaice_lsr in seaice_dynsolver have  
>> been replaced by a loop with a default of 2 iterations, and the  
>> copy/interpolation between time levels has been moved to seaice_lsr.
>>
>> A potential problem for the adjoint are the store directives for  
>> uicec and vicec in the 'predictor time step'. I have moved them to  
>> seaice_lsr along with the rest of the code and I have deliberately  
>> left out the "(icall-1)*ncklev_1 part of the key that is used for  
>> uice/vice, because the storing is only applied for icall==1. I am  
>> not sure if this will work properly and apologize beforehand for  
>> all problems that this may cause.
>>
>> Martin
>>
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>
> ---
> Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
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