[MITgcm-devel] seaice lsr

[Dimitris Menemenlis]

Jinlun, thank you for warning.  Martin could we test convergence before replacing.  I can do this as soon as this meeting is over.  I think that if you run with debuglevel 3 you will get output on number of lsr iterations.  So maybe best to introduce with cpp flag for time being, possibly to become the default if it does not impact convergence.  D.

Dimitris Menemenlis
cell: 818-625-6498

-----Original Message-----

From:  Jinlun Zhang <zhang at apl.washington.edu>
Subj:  Re: [MITgcm-devel] seaice lsr
Date:  Tue Sep 25, 2007 11:56 am
Size:  1K
To:  MITgcm-devel at mitgcm.org

Martin,
The existing code is for relaxation using updated varaibles as soon as 
possible. If you do the change the code may converge slowly.
J

Martin Losch wrote:

> Hi there,
>
> I have found that the LSR solver is a little inconsistent (which  
> causes it to produce a slight assymetry with a symmetric domain and  
> forcing):
> the following lines:
>
>>           URT(I,J)=FXY(I,J,bi,bj)+AA3
>>      &          +UVRT1(I,J,bi,bj)*uIce(I,J-1,1,bi,bj)
>>      &          +UVRT2(I,J,bi,bj)*uIce(I,J+1,1,bi,bj)
>
> (and the corresponding ones for the vice equation) within a J-loop  
> cause URT to be computed from the updated uIce(I,J-1,1,bi,bj) and the  
> not yet updated uIce(I,J+1,1,bi,bj) (=uIce(I,J+1,3,bi,bj) at this  
> time). One could replace these lines by:
>
>>           URT(I,J)=FXY(I,J,bi,bj)+AA3
>>      &          +UVRT1(I,J,bi,bj)*uIce(I,J-1,3,bi,bj)
>>      &          +UVRT2(I,J,bi,bj)*uIce(I,J+1,3,bi,bj)
>
> which changes the results (lab_sea fails with cg2d=10), but then the  
> solution is symmetric, when it should be. Also this formulation  
> removes a dependency from the j-loop which impairs vectorization. Can  
> I change that?
>
> Martin
>
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-- 

Jinlun Zhang
Polar Science Center, Applied Physics Laboratory
University of Washington, 1013 NE 40th St, Seattle, WA 98105-6698

Phone: (206)-543-5569;  Fax: (206)-616-3142
zhang at apl.washington.edu
http://psc.apl.washington.edu/pscweb2002/Staff/zhang/zhang.html

 

 

                         

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