[MITgcm-devel] bling adjoint example

[Patrick Heimbach]

Hi Matt,

please see inlined below.

> On Sep 14, 2016, at 4:38 PM, Matthew Mazloff <mmazloff at ucsd.edu> wrote:
> 
> Hello
> 
> I checked in a bling adjoint example. 
> http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/verification_other/global_oce_biogeo_bling/code_ad/
> 
> Note two files in code_ad that I would rather not have there:
> addummy_in_stepping.F
> external_forcing_surf.F
> 
> In addummy_in_stepping.F
> I had to comment out:
> 152	cmm         CALL ADEXCH_UV_XY_RS( adFu, adFv, .TRUE., myThid )
> 153	cmm         CALL ADEXCH_XY_RS( adQnet, myThid )
> 154	cmm         CALL ADEXCH_XY_RS( adEmPmR, myThid )
> is this a bug?

Not sure what's going on since this piece of code has been around for years, 
but you may have stumbled over a wider problem
(or it may be too late in the day and I am writing nonsense?):

Looking at the common block for addynvars_r that TAF generates
(in file ad_taf_output.f), we get:

      common /addynvars_r/ etan_ad, uvel_ad, vvel_ad, wvel_ad, theta_ad,
     $ salt_ad, gu_ad, gv_ad, gunm1_ad, gvnm1_ad, gtnm1_ad, gsnm1_ad

But looking at the common block we provide 
(in pkg/autodiff/adcommon.h), it is:
      common /addynvars_r/
     &                     adetan,
     &                     aduvel, advvel, adwvel,
     &                     adtheta, adsalt,
     &                     adgu, adgv, adgt, adgs,
#ifdef ALLOW_ADAMSBASHFORTH_3
     &                     adgunm, adgvnm, adgtnm, adgsnm
#else
     &                     adgunm1, adgvnm1, adgtnm1, adgsnm1
#endif

Comparing the two, there are two entries missing in the
new code that TAF generates: adgt, adgs, 
(or rather, gt_ad, gs_ad ,in TAF's newer notation, doesn't matter).

What this means is we may be screwing up the memory by changing/omitting common block entries?
That's not good (or, I can't see right away why this should be benign).

> In external_forcing_surf.F
> I had to add 
> 161	CMM(
> 162	CADJ STORE EmPmR = comlev1, key = ikey_dynamics,  kind = isbyte
> 163	CMM)
> Can/should this be added to main code (perhaps with an ifdef ALLOW_BLING around it. Though I am surprised DIC doesn’t need this too.)

Hard to know without knowing details of bling.
But seems fine with me to commit to main branch with the bracket you suggest.

Cheers
-Patrick

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--------------------------------------------------------
Patrick Heimbach, Ph.D. | http://heimbach.wordpress.com

* The University of Texas at Austin *
The Institute for Computational Engineering and Sciences
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* Massachusetts Institute of Technology *
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