[Mitgcm-support] Re: gmredi_slope_limit

[mitgcm-support at dev.mitgcm.org]

Ralf,

I've solved the problem.
It was indeed a numerical problem related to
very large slope squares (probably related to
very small dSigmaDr's).

Sorry for the false alarm.
Cheers
-Patrick



Ralf Giering wrote:
> Hi Patrick,
> 
> The temporary should not make any difference.
> But I like to have a look at the adjoint differences.
> Can you send me the relevant diff output please.
> 
> Ralf
> 
> On Wednesday 08 January 2003 05:40 pm, you wrote:
> 
>>Hi Ralf,
>>
>>I have another problem in the gmredi_slope_limit routine.
>>I'm not sure whether it's a numerical issue or TAF-related:
>>
>>I am currently testing all tapering schemes.
>>Most of  them look good, but the option
>>        IF (GM_taper_scheme.EQ.'linear') THEN
>>is totally off.
>>
>>I can easily fix it by replacing the expression in this block
>>           ELSE IF ( SlopeSqr(i,j) .GT. maxSlopeSqr )  THEN
>>            taperFct(i,j) = sqrt(maxSlopeSqr / SlopeSqr(i,j))
>>           ENDIF
>>by
>>           ELSE IF ( SlopeSqr(i,j) .GT. maxSlopeSqr )  THEN
>>            tmpfld(i,j) = maxSlopeSqr / SlopeSqr(i,j)
>>            taperFct(i,j) = sqrt(tmpfld(i,j))
>>           ENDIF
>>The latter produces OK gradient checks.
>>
>>I quickly compared the adjoint codes, they seemed OK,
>>but I may have overlooked something.
>>
>>Just want to make sure, there's no bug.
>>
>>Thanks
>>-Patrick
> 
> 


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Patrick Heimbach     Massachusetts Institute of Technology
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