[MITgcm-devel] snapshots and divided.ctrl

[Patrick Heimbach]

Hi Matt,

not sure I understand your question.
If DIVA is enabled (via #define ALLOW_DIVIDED_ADJOINT)
TAF automatically picks the outermost checkpoint level 
(by default ilev_3, in your case ilev_4)
as the interval with which to checkpoint the adjoint snapshots,
because it is here that we tell TAF to do so:
c**************************************
#   ifdef ALLOW_DIVIDED_ADJOINT
CADJ loop = divided
#   endif
c**************************************

There is no extra directive of where the I/O itself should take place,
the natural place to do this is:
* to read the snapshot files right before the ilev_4 loop gets incremented, i.e. before
      do ilev_4 = idivbeg, idivend+1, -1
* to overwrite that snapshot file after that same loop is completed, i.e.
      enddo (of the above loop)

So you should know exactly where in S/R the_main_loop.F TAF will target the read/write, 
namely just before block:
#   ifdef AUTODIFF_4_LEVEL_CHECKPOINT
      do ilev_4 = 1,nchklev_4
         if(ilev_4.le.max_lev4) then

and just after block:
#    ifdef AUTODIFF_4_LEVEL_CHECKPOINT
       endif
      enddo
#    endif

But I guess you know this, so not sure if this helps.

Cheers
-Patrick

On Jun 29, 2012, at 8:07 PM, Matthew Mazloff wrote:

> Hello
> 
> I am having an issue where occasionally the adjoint snapshot files are not properly written out.  I wanted to troubleshoot this and perhaps just change the way the I/O for these files are performed, but I am having trouble figuring out where taf gets the info for snapshots.  Is there a place where we tell taf to write the adjoint state snapshot, or does it do that on its own?  I can't seem to locate in any forward code the call that generates the adjoint code:
> 
> C----------------------------------------------
> C read snapshot
> C----------------------------------------------
> 9813 continue
>      if (idivbeg .lt. nchklev_4) then
>        open(unit=77,file='snapshot'//filen,status='old',form=
>     $'unformatted',iostat=iers)
>        if (iers .eq. 0) then
>          read(unit=77) adapressure0,adapressure1,adaqh0,adaqh1,adarea,
> ...
> 
> and the later write snapshot one either.  How is this information provided to taf?
> 
> 
> Matt
> 
> 
> 
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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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