[Mitgcm-support] Re: TAF bug for tangent linear

[mitgcm-support at dev.mitgcm.org]

Hi Ralf,

thanks for the fixes & improvements.
There is a further little problem:
If I call g_the_main_loop multiple times,
e.g. for forward mode gradient checks,
then g_fc is not re-initialized to zero
(in fact, it's never properly initialized).
That has caused only the first check to be ok
and all the following ones to be off.
I can fix it by reinitialising from the grdchk package,
  but I think it should rather be fixed in TAF.

BTW:
You were right about argument 3 of the exch_uv directives.

Cheers
Patrick

Ralf Giering wrote:

> Hi Patrick,
> 
> I found the bug and fixed it.
> 
> In addition TAF in forward mode was very slow on your code and needed a lot of 
> memory (14 minutes and 1.9Gbyte).
> So, I also worked on the forward mode and was able to reduce time and space
> resources by about a factor of 20 (44sec and 95Mbyte)!
> 
> The new version is already installed.
> 
> Thanks,
> Ralf
> 
> P.S. I think the following flow directives are wrong, argument 3 is not 
> output!
> 
> cadj SUBROUTINE exch_uv_xyz_rl INPUT   = 1, 2, 3, 4
> cadj SUBROUTINE exch_uv_xyz_rl OUTPUT  = 1, 2, 3
> cadj SUBROUTINE exch_uv_xyz_rl ACTIVE  = 1, 2
> cadj SUBROUTINE exch_uv_xyz_rl DEPEND  = 3, 4
> cadj SUBROUTINE exch_uv_xyz_rl ADNAME  = adexch_uv_xyz_rl
> cadj SUBROUTINE exch_uv_xyz_rl FTLNAME = exch_uv_xyz_rl
> 
> On Thursday 12 September 2002 06:10 pm, you wrote:
> 
>>twain.lcs.mit.edu:/scratch/heimbach/ecco/MITgcm/adjoint/
>>
>>make ftltaf
>>
>>ergibt fuer den TAF-Aufruf:
>>
>>~fastopt/bin/taf -forward -ftlmark g_ -i4 -r4 -flow taf_flow.log
>>-nonew_arg  -toplevel the_main_loop -input  '    xx_theta_dummy
>>xx_salt_dummy xx_tr1_dummy xx_hflux_dummy xx_sflux_dummy xx_tauu_dummy
>>xx_tauv_dummy xx_sst_dummy xx_sss_dummy xx_diffkr_dummy xx_kapgm_dummy
>>xx_efluxy_dummy xx_efluxp_dummy' -output 'fc' tamc_code.f
>>
>>Patrick
>>
>>Ralf Giering wrote:
>>
>>>Hi Patrick,
>>>
>>>Das ist eher ein Bug.
>>>Kanst Du mir bitte path und command line geben.
>>>
>>>Ralf
>>>
>>>On Thursday 12 September 2002 05:52 pm, you wrote:
>>>
>>>>Hi Ralf,
>>>>
>>>>es gibt ein Problem mit Version 1.4.12 im forward mode
>>>>(auf twain):
>>>>
>>>>Segmentation fault
>>>>make: *** [ftlmodeltaf] Error 139
>>>>
>>>>reverse mode scheint OK zu sein.
>>>>Vielleicht out of memory?
>>>>
>>>>Patrick
>>>>
>>>>Ralf Giering wrote:
>>>>
>>>>>Hi Patrick,
>>>>>
>>>>>That was indeed a general problem.
>>>>>I have fixed it by saving the input variables on auxiliary variables
>>>>>and reset the input variables before calling the linear routine the
>>>>>second time.
>>>>>
>>>>>I have not choosen the alternative, which is to recalculate the
>>>>>overwritten input variables because, in its extreme, that might require
>>>>>to recompute a lot from scratch. In your example the recomputation is
>>>>>trivial.
>>>>>
>>>>>In addtion TAF gives an information message to the user in this case.
>>>>>I have installed the new version TAF 1.4.12 on through and twain.
>>>>>
>>>>>Ralf
>>>>>
>>>>>On Wednesday 11 September 2002 05:49 pm, you wrote:
>>>>>
>>>>>>Hi Ralf,
>>>>>>
>>>>>>there is a problem with the forward mode of TAF
>>>>>>when exploiting self-adjointness.
>>>>>>
>>>>>>What happens is that in S/R g_solve_for_pressure
>>>>>>cg2d is called first to compute the g_... quantities
>>>>>>(g_cg2d_b,g_cg2d_x),
>>>>>>then called again to calculate the actual state
>>>>>>(cg2d_b,cg2d_x).
>>>>>>Before the second call the indices should be reset, thus
>>>>>>     firstresidual = 0.
>>>>>>     lastresidual = 0.
>>>>>>     numiters = cg2dmaxiters
>>>>>>but the reset is missing.
>>>>>>
>>>>>>The flow directive should have the information,
>>>>>>since the correct resetting is done in the adjoint code:
>>>>>>
>>>>>>C----------------------------------------
>>>>>>C subroutine  cg2d
>>>>>>C----------------------------------------
>>>>>>CADJ SUBROUTINE cg2d ADNAME  = cg2d
>>>>>>CADJ SUBROUTINE cg2d FTLNAME = cg2d
>>>>>>CADJ SUBROUTINE cg2d INPUT   = 1,2,3,4,5,6
>>>>>>CADJ SUBROUTINE cg2d OUTPUT  =   2,3,4,5
>>>>>>CADJ SUBROUTINE cg2d ACTIVE  = 1,2
>>>>>>CADJ SUBROUTINE cg2d DEPEND  =           6
>>>>>>
>>>>>>
>>>>>>Another issue (or, why I do all this) is that
>>>>>>I try to do forward mode vs. finite difference gradient checks.
>>>>>>Assuming that
>>>>>>  g_fc = (grad J)_(ith-component) * (delta xx)_(ith-component)
>>>>>>I should be able to recover (grad J)_(ith-component)
>>>>>>by setting
>>>>>>  (delta xx)_(ith-component) = 1.
>>>>>>(all others = 0.).
>>>>>>Well, I get the correct order of magnitude,
>>>>>>but not really correct gradients.
>>>>>>Do you have an idea what else could go wrong
>>>>>>(I've tried it with my above hand-fix).
>>>>>>
>>>>>>Cheers
>>>>>>Patrick
>>>>>>
> 


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Patrick Heimbach     Massachusetts Institute of Technology
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