View source for Compiling GCHP

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#[[GCHP_Hardware_and_Software_Requirements|Hardware and Software Requirements]]
#[[Downloading_GCHP|Downloading Source Code and Data Directories]]
#[[Obtaining_a_GCHP_Run_Directory|Obtaining a Run Directory]]
#[[Setting_Up_the_GCHP_Environment|Setting Up the GCHP Environment]]
#<span style="color:blue">'''Compiling'''</span>
#[[Running_GCHP:_Basics|Running GCHP: Basics]]
#[[Running_GCHP:_Configuration|Running GCHP: Configuration]]
#[[GCHP_Output_Data|Output Data]]
#[[Developing_GCHP|Developing GCHP]]
#[[GCHP_Run_Configuration_Files|Run Configuration Files]]
<br>

== Overview ==

This section provides instructions on how to clean and compile GCHP. There are several options for cleaning and compiling which allow clean and compilation of subsets of modules, thereby minimizing recompilation to only modules you have modified.

You are ready to compile GCHP after you have obtained the GCHP source code, set up your run directory, and set your environment. First time compilation can take a while (30 minutes or more) because it requires building large modules, including [https://www.earthsystemcog.org/projects/esmf/ ESMF], [https://geos5.org/wiki/index.php?title=MAPL_software MAPL], [https://www.gfdl.noaa.gov/fv3/ FV3 dycore advection], and GEOS-Chem. MAPL, which is short for Modeling, Analysis and Prediction Layer, is built on ESMF, aka the Earth System Modeling Framework. Both systems are highly flexible but highly complex, with significant compilation times. Fortunately, MAPL and ESMF do not need to be recompiled unless parts of their code have been modified which is usually not necessary. Subsequent compile times will therefore be significantly shorter, on the same order of magnitude as compiling GEOS-Chem Classic.

If you run into problems compiling GCHP and cannot figure out why, please create an issue on the GCHP issue tracker located at [https://github.com/geoschem/gchp/issues https://github.com/geoschem/gchp/issues].

== Run Directory Makefile ==

The GCHP run directory <tt>Makefile</tt> contains several options for cleaning and compiling source code, as well as utility options you might find useful. Options are printed out by typing the following at the command line:

 make help

We encourage you to do this and browse the options available. Several options are particularly useful for cleaning up files in your run directory and displaying the status of your source code.

=== Initial Compile ===

To compile GCHP from scratch, navigate to your run directory and check that your <tt>gchp.env</tt> symbolic link is pointing to the environment file you wish to use. Next, type the following within the run directory:

 make clean
 make build

These commands will execute <tt>./build.sh clean</tt> and <tt>./build.sh build</tt>. All build information is sent to both the terminal window and to a log file called <tt>compile.log</tt>. Git information for both source code repositories at compile time are recorded in a separate file called <tt>lastbuild</tt> for future reference. Upon successful compilation, the following empty files are created in your GCHP source code directories:
* <tt>GCHP/ESMF/esmf.install</tt>
* <tt>GCHP/Shared/mapl.install</tt>
* <tt>GCHP/FVdycoreCubed_GridComp/fvdycore.install</tt>

These files indicate successful compilation per module and their presence prompts the GCHP source code <tt>Makefile</tt> to skip compiling each component during future builds unless you explicitly clean the source code. If you are ever uncertain on whether your ESMF, MAPL, and FV3 dycore were previously built, check if these files exist.

=== Recompile ===

For subsequent GCHP compilations you have several options. You can remind yourself of all options by typing the following at the prompt from within your run directory:

 make help

For compilation the make targets you are interested in are clean, clean_mapl, clean_gc, build, build_mapl, build_gc, and build_gc_debug. Here is a brief summary of these options.

Clean/compile ALL source code, including ESMF, MAPL, and FV3:
 make clean
 make build

Clean/compile all source code except ESMF:
 make clean_mapl
 make build_mapl

Clean/compile all source code except ESMF, MAPL, and FV3:
 make clean_gc
 make build_gc

Same as above but compile GEOS-Chem with debug flags turned on (note that this will slow down the model)
 make build_gc_debug

A typical workflow would be:
#create a run directory
#compile from scratch (make clean; make build)
#edit GEOS-Chem code in GeosCore
#recompile with debug flags on (make build_gc_debug)
#do a short test run to see if any of the debug flags trigger a problem
#recompile with debug flags off (make build_gc) to speed up the model

The last few steps would be repeated as needed. Since this workflow is the most common, the default make target, meaning the target used when none is specified, is set to build_gc. Therefore to rebuild GEOS-Chem after changing GEOS-Chem files or any high-level files in the GCHP directory you can simply type this:

 make

Note that if you change your underlying libraries (configured in your environment file) you MUST do a full source code clean before rebuilding. Otherwise you will likely encounter a segmentation fault when running the model. For this reason it is recommended that you create a new run directory for each new environment you want to run in, e.g. if you want to test with both Intel and GNU fortran compilers.

Also note that these build targets were added in GCHP version 12.2.0. If you are using an earlier version type <tt>make help</tt> to view your make options.

== Compilation Tips ==

If a GCHP executable exists in the GEOS-Chem bin/ folder to be copied to your run directory, then you should see the following message at the end of compilation:

 ###################################
 ### GCHP compiled successfully! ###
 ###################################

If you did a clean compile of you code and you see this message then you know that GCHP compiled without error. Compiler output, including warnings and error messages, will be stored in a log file called <tt>compile.log</tt>. If you inspect your log file or watch the compile output real-time, you will notice that there are many warnings and error messages. Many of these errors are due to leftover components in MAPL which are no longer used but which still try to compile. As long as the compilation continues, these errors can almost always be ignored and they will have no effect on the operation of GCHP. 

If you are recompiling your source code and see this message then your compilation may or may not have been successful. Why? Because compilation may fail but the previous executable may still be available to be copied, which is the criteria for this message.

The general rule-of-thumb is if you clean compile or if you build using 'make build_gc' and therefore skip building MAPL, then you can trust the 'GCHP compiled successfully' message. However, if you recompile using 'make build_mapl' without cleaning first, then you will need to dig a little deeper to ensure a successful rebuild. The best way to do this is to do keyword search for 'making install' in <tt>compile.log</tt> and scan the few lines directly above all instances of it. If there was a problem with MAPL you will spot it immediately in one of these areas. If you plan on developing within MAPL please make sure you fully understand this approach to debugging MAPL since it will save you a lot of time and frustration.

Why is this necessary? It is because MAPL will continue to compile even if a compile error occurs. MAPL compilation involves compiling a series of components, many of them dependent on components that came before, and compilation rules are relaxed to allow minor problems. One component may fail compilation but the compilation will not crash until the built file is needed later on in the build sequence. It is therefore necessary to search your log file for errors high above the final error in the event of compile failure. The log file will be long so this should be done by keyword search. 

While this has already been stated, we will state it again since it is so useful. Here are strategies that typically hone in immediately on the original MAPL error:

# Search for string "making install" look at the lines immediately above all results of your keyword search.
# A second and more tedious option is to search for string "error". Ignore results where error is in a filename or in a source code string that triggered a warning.

Here are some tips for troubleshooting this sort of problem.

# Check your compilation log file for errors using the guidelines presented above.
# If in doubt, check the source code directory to see the file times. If the binary for the file you updated is older than the other binaries then it encountered a compile error in your update.

== Advanced Compilation Topics ==

The <tt>Makefile</tt> in the run directory invokes a bash shell script called <tt>build.sh</tt> that includes changing into the source code directory and invoking source code Makefiles. At its core, building GCHP simply requires the inclusion of additional target <tt>HPC=yes</tt> if cleaning and <tt>hpc</tt> if compiling when invoking make in the GEOS-Chem repository. Cleaning GCHP also requires changing into the GCHP directory explicitly to clean ESMF, MAPL, and FV3 dycore.

If you are interested in seeing the core <tt>make</tt> commands used for all options provided in the run directory <tt>Makefile</tt>, see the commands defined in <tt>build.sh</tt>. You can then trace the build sequence by looking at the Makefiles in the GEOS-Chem and GCHP repositories. Note that calling <tt>make</tt> always invokes the <tt>Makefile</tt> in the directory you are in and changing into the GEOS-Chem and GCHP source code directories occurs within <tt>build.sh</tt>. Also note that the <tt>GRID=4x5</tt> argument has no effect on the resolution at which the model runs since GCHP functions on the cubed-sphere grid. However, passing <tt>GRID</tt> is required so that components of GEOS-Chem Classic are functional.

If you are interested in the build sequence for MAPL, look at the various *.mk files <tt>ESMA_base.mk</tt>, <tt>ESMA_arch.mk</tt>, and <tt>GMAO_base.mk</tt> in <tt>GCHP/Shared/Config</tt> as well as <tt>GNUMakefile</tt> within <tt>GCHP/Shared</tt> and all its subdirectories. Also see <tt>GIGC.mk</tt> in the highest level of the GCHP repository for the include dependencies between GCHP modules.

Currently GCHP does not compile with cmake but work is in progress to make this possible in the future.

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'''''[[Setting Up the GCHP Environment|Previous]] | [[GCHP_Basic_Example_Run|Next]] | [[Getting_Started_With_GCHP|User Manual Home]] | [[GEOS-Chem_HP|GCHP Home]]'''''