[MITgcm-support] Nonlinear free surface and the adjoint

[Patrick Heimbach]

Hi Christopher, 

there shouldn’t be too many recomputation warnings.
The devil is in the details, as usual, so would be good to know what 
specific warnings you get.
As a good starting point of a set of CPP options, take a look at either
MITgcm/verification/global_ocean.cs32x15/code_ad/CPP_OPTIONS.h
or at the ECCO v4 config. in
MITgcm_contrib/gael/verification/global_oce_llc90/code/CPP_OPTIONS.h

Both use NLFS as well as z* (zstar) in forward and adjoint
(the former being a more lightweight configuration that is tested
on a nightly basis).

An important part is to disable the SIGMA_CODE,
which we haven’t pushed through TAF (nor OpenAD) yet, i.e. set:
#define NONLIN_FRSURF
# undef DISABLE_RSTAR_CODE
#define DISABLE_SIGMA_CODE

-Patrick



On May 29, 2014, at 1:45 PM, Christopher L. P. Wolfe <christopher.wolfe at stonybrook.edu> wrote:

> Hi all,
> 
> I’m trying to do sensitivity studies using a nonlinear free surface. TAF gives warnings about extensive recomputations that disappear when I turn off the NLFS using #undef NONLIN_FRSURF in CPP_OPTIONS. I’ve heard that ECCOv4 uses the NLFS in both forward and adjoint mode, so either the recomputations are not that bad or there’s a way to make them go away. Does anyone know which is the case?
> 
> If neither, is there a flag I could set to use the NLFS for the forward integration but have it turned off in the adjoint?
> 
> Thanks,
> Christopher
> 
> 
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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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