[MITgcm-support] Adjoins advection schemes

[Patrick Heimbach]

Chris,

I've just made some code changes to try to enable SOM in the adjoint.
It passes at least simple gradient checks, which is necessary,
but by no means sufficient
(have added an extra verification in tutorial_tracer_adjsens/).

If you feel courageous you could give it a try.
Update code to the latest (after making sure that you have a 
backup of your current working version ;) 

Then, in GAD_OPTIONS.h set:
#define GAD_ALLOW_TS_SOM_ADV

and in data set:
 multiDimAdvection=.TRUE.,
 tempAdvScheme=81,
 saltAdvScheme=81,
(or 80 for non-flux-limited version).

There remain some recomputation inefficiencies, but I think (hope)
they can be tolerated at this point.
Would be curious to know how it goes.

Happy 14th of July
-Patrick



On Jul 2, 2012, at 2:54 PM, Christopher L. P. Wolfe wrote:

> 
> Thanks Patrick,
> 
> TAF choked on OS7MP, but DST3 seems to be working well for the moment.
> 
> Cheers,
> Christopher
> 
> On Jul 2, 2012, at 6:41 AM, Patrick Heimbach wrote:
> 
>> 
>> Christopher,
>> 
>> our scheme of choice for the adjoint has become
>> 3rd-order direct space and time DST3 in non-flux limited form, i.e. scheme 30.
>> DST3FL (33) causes problems for certain applications, and we haven't followed up on this
>> (the obvious issue being how the limiters are formulated).
>> 
>> SOM is very memory-consuming, so we've staid away from this one for the adjoint
>> (which amplifies memory-consumption).
>> 
>> OS7MP is also currently disabled but might be worth a try
>> (would need some tweak though before it can be attempted).
>> 
>> -Patrick
>> 
>> On Jul 2, 2012, at 3:58 AM, Martin Losch wrote:
>> 
>>> Christopher, 
>>> 
>>> the easiest way to find out is to have a look at gad_advection or gad_calc_rhs (the calls to GAD_*_ADV_X/Y). You'll see that most schemes "work" (i.e., they are allowed to be used) but in particular OS7MP (and I think SOM) doesn't work. From my experience I recommend using linear advection schemes (which rules out all flux limited schemes) for more accurate gradients.  
>>> 
>>> Martin
>>> 
>>> On Jun 29, 2012, at 10:25 PM, Christopher L. P. Wolfe wrote:
>>> 
>>>> Hi all,
>>>> 
>>>> Does anyone know if there exists a list of advection schemes which are known to "work" with adjoint? I'm particular interested in the higher order schemes like OS7MP and SOM and their flux limited forms. 
>>>> 
>>>> Thanks in advance,
>>>> Christopher
>>>> 
>>>> 
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>>> 
>>> 
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>> 
>> ---
>> Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
>> MIT | EAPS 54-1420 | 77 Massachusetts Ave | Cambridge MA 02139 USA
>> FON +1-617-253-5259 | FAX +1-617-253-4464 | SKYPE patrick.heimbach
>> 
>> 
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> 
> 
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---
Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
MIT | EAPS 54-1420 | 77 Massachusetts Ave | Cambridge MA 02139 USA
FON +1-617-253-5259 | FAX +1-617-253-4464 | SKYPE patrick.heimbach


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