The CCSM2'0 Quick Start Guide

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The CCSM2.0 Quick Start Guide
Lawrence Buja CCSM Software Engineering Group
ccsm_at_ucar.edu June 29 2002
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CCSM2.0 Quick Start Guide

• What is needed to run CCSM2?
• Downloading the CCSM2.0 distribution
• The CCSM source code
• Input datasets
• Building the CCSM
• Running the CCSM
• CCSM output data

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What is needed to run CCSM2?

• OS IBM AIX or SGI IRIX64
• Compilers Fortran 90, C
• Tools gunzip, gnumake, Perl5, Perl/Tk
• Permanent Temporary disk space
• Libraries MPI and netCDF
• Input data 0.2 GB for T31_gx3 grid,
  0.8 GB for T42_gx1v3 grid
• CCSM2 source code 35 MB

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The CCSM2.0 distribution

• CCSM2.0 is available via the web from
• http//www.cgd.ucar.edu/csm/models/ccsm2.0
• ccsm2.0.tar.gz
  CCSM2.0 source codes
• ccsm2.0.inputdata.T42_gx1v3.tar input
  data for T42_gx1v3 resolution
• ccsm2.0.inputdata.T31_gx3.tar input
  data for T31_gx3 resolution
• ccsm2.0.inputdata.T62.tar latm
  data for T62 resolution
• ccsm2.0.inputdata.CLM_SPINUP_FILES.tar are CLM
  datasets
• gunzip -c ccsm2.0.tar.gz tar -xf -
• tar -xf ccsm2.0.inputdata.T42_gx1v3.tar
  

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The CCSM distribution
ccsm2.0.tar.gz (35 Mbytes) Scripts Model Code
ccsm2.0.inputdata.T42_gx1v3.tar (.8 Gbytes
) Initial data
/fs/LOGNAME/
HOME/
inputdata/ CSMDATA
ccsm2.0/ CSMROOT
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The CCSM source code inputdata/
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The CCSM source code Top Level
(CSMROOT)
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The CCSM source code models/
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The CCSM source code scripts/
test.a1.run cpl.setup.csh atm.setup.csh ocn.setup.
csh ice.setup.csh lnd.setup.csh datm.setup.csh doc
n.setup.csh dice.setup.csh dlnd.setup.csh ccsm_arc
hive test.a1.har
ccsm_gui.pl
ccsm_checkenvs ccsm_cpdata ccsm_getfile ccsm_getin
put ccsm_getrestart ccsm_msmkdir ccsm_msread ccsm_
mswrite ccsm_splitdf modules.AIX.seaborg modules.I
RIX64.nirvana modules.IRIX64.ute test.a1.mods.
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Building the CCSM

• Three levels of c-shell scripts are used
• Run script builds runs CCSM (i.e. test.a1.run)
• Define the CCSM environment
• Run each component setup script
• Execute all components simultaneously
• Setup scripts builds each model (i.e.
  ice.setup.csh)
• Position any input data needed by that component
• Generate the component's namelist input file
• Build the component executable
• Utility tools (i.e. ccsm_getinput)

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Building the CCSM

• A sample run script (test.a1.run) is distributed.
• Functional summary of test.a1.run
• setenv A abc
• setenv B xyz
• foreach i (cpl atm ocn ice lnd)
• i.setup.csh
• end
• mpirun cpl atm ocn ice lnd
• exit

Define environment
Loop over setup scripts
Run CCSM
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Building the CCSM CASE

• CASE identifies a CCSM run.
• The sample CASE is test.a1,
• CASE for the CCSM control run is b20.007
• To define a new CASE
• Copy all of test.a1/ into CASE/
• rename test.a1.run to CASE.run
• Modify the main run script
• CASE CASESTR CSMROOT CSMDATA EXEROOT ARCROOT
• HOME/ccsm2.0/scripts/CASE/CASE.run submitted
  to the batch queue.

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Building the CCSM
Initial data
Scripts Model Code
HOME/ccsm2.0/ CSMROOT
/fs/LOGANME/inputdata/ CSMDATA
doc/
models/
scripts/
Large model build/execute directories
/ptmp/LOGNAME/CASE EXEROOT
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Methods for starting the CCSM

• New CCSM case is started as either a startup,
  hybrid or branch run, depending on the science
  requirements.
• startup new run from arbitrary input files
• hybrid new run from initial or restart files
• branch new run from restart files
• continue extend an existing run exactly

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General concepts Exact Restarts

• Wall-clock limits in the batch queues typically
  restrict runs to a finite length, usually 1-3
  model years.
• At specified intervals, restart and initial files
  will be created by all components
• Runs are extended as "continue" runs.
• A continued run must give exactly the same
  results as if the run had never stopped.

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Exact Restarts

• Are your results reproducible?
• Factors
• Any change in machine architecture
• Any change in math libraries
• Running on different number of processors
• Changes you've made to the code
• Additional variables added to model not
• properly written to restart files

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Changing the code

• Frozen Code
• Keep the CCSM2.0 model code "frozen"
• To introduce code changes
• copy specific model files to new directory
• modify the new copies of model code
• tell the model setup scripts to get the modified
  code from the new directory first, then get
  rest of unchanged model code from the
  "frozen" version
• This method encapsulates modified code
• Use same "frozen code" for different work

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Changing the code

• Three levels of change
• 1. "Bit-for-bit" (no change to answers)
• adding/subtracting output
• 2. Machine-level (answers similar at the bit
  level)
• Changes in operation order
• Changes in math libraries
• changes in compiler options/flags/versions
• 3. Algorithm changes (answers change)
• Different parameterization
• Rerun control integration

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CCSM Components
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CCSM2 Performance

• OCN
• ICE
• LND
• ATM
• CPL

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Output log files

• The printed output from each CCSM component is
  saved in a "log file" A coordinated timestamp
  links filenames
• LID is of the form YYMMDD-hhmmss, where YYMMDD
  are the Year, Month, Day and hhmmss are hour,
  minute and second that the run began (i.e.
  EXEROOT/ocn/ocn.log.000626-082714) .

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History and restart output data

• Default netCDF monthly averaged history files
  for all components in netCDF format.
• CCSM2.0 also writes out binary restart files from
  all components at regular intervals.
• The total output volume of the model output can
  vary greatly depending upon the output
  frequencies and options selected.

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CCSM Yearly Output (b20.014)
cpl atm ocn ice lnd
1.4 Gbytes 0.7 Gbytes 4.1 Gbytes .6 Gbytes
.4 Gbytes
Tape Archive Devices
7.4 Gbytes/year
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Getting help

• http//www.ccsm.ucar.edu forum
• ccsm_at_ucar.edu