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Subsections
5.2.3 The AD build process in detail
The make <MODE>all target consists of the following procedures:
- A header file AD_CONFIG.h is generated which contains a CPP option
on which code ought to be generated. Depending on the make target,
the contents is one of the following:
- #define ALLOW_ADJOINT_RUN
- #define ALLOW_TANGENTLINEAR_RUN
- #define ALLOW_ECCO_OPTIMIZATION
- A single file <MODE>_input_code.f is concatenated
consisting of all .f files that are part of the list AD_FILES
and all .flow files that are part of the list AD_FLOW_FILES.
- The AD tool is invoked with the <MODE>_<TOOL>_FLAGS.
The default AD tool flags in genmake2 can be overrwritten by
an adjoint_options file (similar to the platform-specific
build_options, see Section ???.
The AD tool writes the resulting AD code into the file
<MODE>_input_code_ad.f
- A short sed script adjoint_sed is applied to
<MODE>_input_code_ad.f
to reinstate myThid into the CALL argument list of active file I/O.
The result is written to file <MODE>_<TOOL>_output.f.
- All routines are compiled and an executable is generated
(see Table ???).
Not all routines are presented to the AD tool.
Routines typically hidden are diagnostics routines which
do not influence the cost function, but may create
artificial flow dependencies such as I/O of active variables.
genmake2 generates a list (or variable) AD_FILES
which contains all routines that are shown to the AD tool.
This list is put together from all files with suffix .list
that genmake2 finds in its search directories.
The list file for the core MITgcm routines is in model/src/
is called model_ad_diff.list.
Note that no wrapper routine is shown to TAF. These are either
not visible at all to the AD code, or hand-written AD code
is available (see next section).
Each package directory contains its package-specific
list file <PKG>_ad_diff.list. For example,
pkg/ptracers/ contains the file ptracers_ad_diff.list.
Thus, enabling a package will automatically extend the
AD_FILES list of genmake2 to incorporate the
package-specific routines.
Note that you will need to regenerate the Makefile if
you enable a package (e.g. by adding it to packages.conf)
and a Makefile already exists.
TAMC and TAF can evaluate user-specified directives
that start with a specific syntax (CADJ, C$TAF, !$TAF).
The main categories of directives are STORE directives and
FLOW directives. Here, we are concerned with flow directives,
store directives are treated elsewhere.
Flow directives enable the AD tool to evaluate how it should treat
routines that are 'hidden' by the user, i.e. routines which are
not contained in the AD_FILES list (see previous section),
but which are called in part of the code that the AD tool does see.
The flow directive tell the AD tool
- which subroutine arguments are input/output
- which subroutine arguments are active
- which subroutine arguments are required to compute the cost
- which subroutine arguments are dependent
The syntax for the flow directives can be found in the
AD tool manuals.
genmake2 generates a list (or variable) AD_FLOW_FILES
which contains all files with suffix.flow that it finds
in its search directories.
The flow directives for the core MITgcm routines of
eesupp/src/ and model/src/
reside in pkg/autodiff/.
This directory also contains hand-written adjoint code
for the MITgcm WRAPPER (section 4).
Flow directives for package-specific routines are contained in
the corresponding package directories in the file
<PKG>_ad.flow, e.g. ptracers-specific directives are in
ptracers_ad.flow.
The storing that is required at each period of the
3-level checkpointing is controled by three
top-level headers.
do ilev_3 = 1, nchklev_3
# include ``checkpoint_lev3.h''
do ilev_2 = 1, nchklev_2
# include ``checkpoint_lev2.h''
do ilev_1 = 1, nchklev_1
# include ``checkpoint_lev1.h''
...
end do
end do
end do
All files checkpoint_lev?.h are contained in directory
pkg/autodiff/.
Next: 5.2.4 The cost function
Up: 5.2 TLM and ADM
Previous: 5.2.2 Building the AD
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