[MITgcm-support] diagnosing problems with the adjoint

[Matthew Mazloff]

Hi Holly,

Your adjoint is definitely blowing up (how many timesteps is your grad  
check....its blowing up fast).   Try turning off packages when you run  
the adjoint and see if that helps.  Are you using the divided  
adjoint?  If so you can just change some things to false in data.pkg  
when its about to start.  Turn off KPP and GMREDI and packages of that  
nature.  If you are not using the divided adjoint then you have to use  
autodiff_inadmode_set.F to turn these things off.  In this file just set
       usePtracers  = .FALSE.
       useKPP = .FALSE.
       useGMREDI = .FALSE.
       useSEAICE = .FALSE.

Then try again

-Matt

ps> out of curiosity, what viscosity and diffusivity are you trying to  
run the adjoint with?

Oh, and also some of the advection schemes may not be stable.  I am  
using
  multiDimAdvection=.FALSE.,
  tempAdvScheme=30,
  saltAdvScheme=30,


   pps> of course the real expert is just upstairs from you -- bug  
him :o)




On Aug 12, 2009, at 8:14 AM, Holly Dail wrote:

> Hello all -
>
> I'd like to use optimization with a regional North Atlantic setup.   
> As a first case, I started with the approach laid out in  
> tutorial_global_oce_optim --
> - cost based on (1) divergence of annual mean surface temperatures  
> in the model from climatology and (2) reasonable magnitude of  
> control vector
> - control is a time-mean heat flux correction (2-d field)
>
> My sensitivities are astronomical (i.e. adxx = 10^16), the gradient  
> check seems to fail (as shown below, finite difference gradients  
> seem okay, adjoint gradients not so much), and optim.x fails with  
> message 'the linesearch failed'.
>
> (PID.TID 0000.0001) grdchk output:            procId                
> I        ITIL  EPOS        JTILEPOS           LAYER             
> X(I)      X(I)+/-EPS
> (PID.TID 0000.0001) grdchk output:            FC              
> FC1             FC2 FC1-FC2/(2*EPS)    ADJ GRAD(FC)   1-FDGRD/ADGRD
> (PID.TID 0000.0001) grdchk output:                 0                
> 1             56              35               1 0.000000000D+00 -. 
> 100000000D+00
> (PID.TID 0000.0001) grdchk output:                   0.261232434D+02  
> 0.261232444     D+02 0.261232340D+02 0.523051129D-04 -.115313924+108  
> 0.100000000D+01
>
> I suppose this may mean the adjoint is blowing up?  I've tried  
> reducing my time step and increasing viscosity and I checked that my  
> climatology & error fields are defined at all wet points; are there  
> other fixes folks have had success with?  Also if you have scripts  
> that you use to diagnose your optimization runs that would be really  
> appreciated.
>
> Thanks -
> Holly
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