/[MITgcm]/manual/s_getstarted/text/getting_started.tex

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-revision 1.1.1.1 by adcroft,
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+revision 1.44 by jmc,
Mon Aug 30 23:09:20 2010 UTC
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  % $Header$
  % $Name$
+ %\section{Getting started}
- \begin{center}
+ We believe the best way to familiarize yourself with the
- {\Large \textbf{Using the model}}
+ model is to run the case study examples provided with the base
+ version. Information on how to obtain, compile, and run the code is
- \vspace*{4mm}
+ found here as well as a brief description of the model structure
+ directory and the case study examples. Information is also provided
- \vspace*{3mm} {\large July 2001}
+ here on how to customize the code when you are ready to try implementing
- \end{center}
+ the configuration you have in mind.  The code and algorithm
+ are described more fully in chapters \ref{chap:discretization} and
+ \ref{chap:sarch}.
+ \section{Where to find information}
+ \label{sec:whereToFindInfo}
+ \begin{rawhtml}
+ <!-- CMIREDIR:whereToFindInfo: -->
+ \end{rawhtml}
+ There is a web-archived support mailing list for the model that
+ you can email at \texttt{MITgcm-support@mitgcm.org} or browse at:
+ \begin{rawhtml} <A href=http://mitgcm.org/mailman/listinfo/mitgcm-support/ target="idontexist"> \end{rawhtml}
+ \begin{verbatim}
+ http://mitgcm.org/mailman/listinfo/mitgcm-support/
+ http://mitgcm.org/pipermail/mitgcm-support/
+ \end{verbatim}
+ \begin{rawhtml} </A> \end{rawhtml}
+ \section{Obtaining the code}
+ \label{sec:obtainingCode}
+ \begin{rawhtml}
+ <!-- CMIREDIR:obtainingCode: -->
+ \end{rawhtml}
+ MITgcm can be downloaded from our system by following
+ the instructions below. As a courtesy we ask that you send e-mail to us at
+ \begin{rawhtml} <A href=mailto:MITgcm-support@mitgcm.org> \end{rawhtml}
+ MITgcm-support@mitgcm.org
+ \begin{rawhtml} </A> \end{rawhtml}
+ to enable us to keep track of who's using the model and in what application.
+ You can download the model two ways:
+ \begin{enumerate}
+ \item Using CVS software. CVS is a freely available source code management
+ tool. To use CVS you need to have the software installed. Many systems
+ come with CVS pre-installed, otherwise good places to look for
+ the software for a particular platform are
+ \begin{rawhtml} <A href=http://www.cvshome.org/ target="idontexist"> \end{rawhtml}
+ cvshome.org
+ \begin{rawhtml} </A> \end{rawhtml}
+ and
+ \begin{rawhtml} <A href=http://www.wincvs.org/ target="idontexist"> \end{rawhtml}
+ wincvs.org
+ \begin{rawhtml} </A> \end{rawhtml}
+ .
+ \item Using a tar file. This method is simple and does not
+ require any special software. However, this method does not
+ provide easy support for maintenance updates.
- In this part, we describe how to use the model. In the first section, we
+ \end{enumerate}
- provide enough information to help you get started with the model. We
- believe the best way to familiarize yourself with the model is to run the
- case study examples provided with the base version. Information on how to
- obtain, compile, and run the code is found there as well as a brief
- description of the model structure directory and the case study examples.
- The latter and the code structure are described more fully in sections 2 and
-, respectively. In section 4, we provide information on how to customize
- the code when you are ready to try implementing the configuration you have
- in mind.
- \section{Getting started}
+ \subsection{Method 1 - Checkout from CVS}
+ \label{sec:cvs_checkout}
- \subsection{Obtaining the code}
+ If CVS is available on your system, we strongly encourage you to use it. CVS
+ provides an efficient and elegant way of organizing your code and keeping
+ track of your changes. If CVS is not available on your machine, you can also
+ download a tar file.
- The reference web site for the model is:
+ Before you can use CVS, the following environment variable(s) should
+ be set within your shell.  For a csh or tcsh shell, put the following
  \begin{verbatim}
- http://mitgcm.org
+ % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/gcmpack
  \end{verbatim}
+ in your \texttt{.cshrc} or \texttt{.tcshrc} file.  For bash or sh
- On this site, you can download the model as well as find useful information,
+ shells, put:
- some of which might overlap with what is written here. There is also a
- support news group for the model located at (send your message to \texttt{%
- support@mitgcm.org}):
  \begin{verbatim}
- news://mitgcm.org/mitgcm.support
+ % export CVSROOT=':pserver:cvsanon@mitgcm.org:/u/gcmpack'
  \end{verbatim}
+ in your \texttt{.profile} or \texttt{.bashrc} file.
- If CVS is available on your system, we strongly encourage you to use it. CVS
- provides an efficient and elegant way of organizing your code and keeping
- track of your changes. If CVS is not available on your machine, you can also
- download a tar file.
- \subsubsection{using CVS}
- Before you can use CVS, the following environment variable has to be set in
+ To get MITgcm through CVS, first register with the MITgcm CVS server
- your .cshrc or .tcshrc:
+ using command:
  \begin{verbatim}
- % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/u0/gcmpack
  % cvs login ( CVS password: cvsanon )
  \end{verbatim}
+ You only need to do a ``cvs login'' once.
- You only need to do ``cvs login'' once. To obtain the latest source:
+ To obtain the latest sources type:
  \begin{verbatim}
- % cvs co -d directory models/MITgcmUV
+ % cvs co MITgcm
  \end{verbatim}
+ or to get a specific release type:
- This creates a directory called \textit{directory}. If \textit{directory}
- exists this command updates your code based on the repository. Each
- directory in the source tree contains a directory \textit{CVS}. This
- information is required by CVS to keep track of your file versions with
- respect to the repository. Don't edit the files in \textit{CVS}! To obtain a
- specific \textit{version} that is not the latest source:
  \begin{verbatim}
- % cvs co -d directory -r version models/MITgcmUV
+ % cvs co -P -r checkpoint52i_post  MITgcm
  \end{verbatim}
+ The MITgcm web site contains further directions concerning the source
- \subsubsection{other methods}
+ code and CVS.  It also contains a web interface to our CVS archive so
+ that one may easily view the state of files, revisions, and other
- You can download the model as a tar file from the reference web site at:
+ development milestones:
+ \begin{rawhtml} <A href="http://mitgcm.org/viewvc/MITgcm/MITgcm/" target="idontexist"> \end{rawhtml}
+ \begin{verbatim}
+ http://mitgcm.org/viewvc/MITgcm/MITgcm/
+ \end{verbatim}
+ \begin{rawhtml} </A> \end{rawhtml}
+ As a convenience, the MITgcm CVS server contains aliases which are
+ named subsets of the codebase.  These aliases can be especially
+ helpful when used over slow internet connections or on machines with
+ restricted storage space.  Table \ref{tab:cvsModules} contains a list
+ of CVS aliases
+ \begin{table}[htb]
+   \centering
+   \begin{tabular}[htb]{|lp{3.25in}|}\hline
+     \textbf{Alias Name}    &  \textbf{Information (directories) Contained}  \\\hline
+     \texttt{MITgcm\_code}  &  Only the source code -- none of the verification examples.  \\
+     \texttt{MITgcm\_verif\_basic}
+     &  Source code plus a small set of the verification examples
+     (\texttt{global\_ocean.90x40x15}, \texttt{aim.5l\_cs}, \texttt{hs94.128x64x5},
+     \texttt{front\_relax}, and \texttt{plume\_on\_slope}).  \\
+     \texttt{MITgcm\_verif\_atmos}  &  Source code plus all of the atmospheric examples.  \\
+     \texttt{MITgcm\_verif\_ocean}  &  Source code plus all of the oceanic examples.  \\
+     \texttt{MITgcm\_verif\_all}    &  Source code plus all of the
+     verification examples. \\\hline
+   \end{tabular}
+   \caption{MITgcm CVS Modules}
+   \label{tab:cvsModules}
+ \end{table}
+ The checkout process creates a directory called \texttt{MITgcm}. If
+ the directory \texttt{MITgcm} exists this command updates your code
+ based on the repository. Each directory in the source tree contains a
+ directory \texttt{CVS}. This information is required by CVS to keep
+ track of your file versions with respect to the repository. Don't edit
+ the files in \texttt{CVS}!  You can also use CVS to download code
+ updates.  More extensive information on using CVS for maintaining
+ MITgcm code can be found
+ \begin{rawhtml} <A href="http://mitgcm.org/public/using_cvs.html" target="idontexist"> \end{rawhtml}
+ here
+ \begin{rawhtml} </A> \end{rawhtml}
+ .
+ It is important to note that the CVS aliases in Table
+ \ref{tab:cvsModules} cannot be used in conjunction with the CVS
+ \texttt{-d DIRNAME} option.  However, the \texttt{MITgcm} directories
+ they create can be changed to a different name following the check-out:
+ \begin{verbatim}
+    %  cvs co MITgcm_verif_basic
+    %  mv MITgcm MITgcm_verif_basic
+ \end{verbatim}
+ \subsubsection{Upgrading from an earlier version}
+ If you already have an earlier version of the code you can ``upgrade''
+ your copy instead of downloading the entire repository again. First,
+ ``cd'' (change directory) to the top of your working copy:
+ \begin{verbatim}
+ % cd MITgcm
+ \end{verbatim}
+ and then issue the cvs update command such as:
+ \begin{verbatim}
+ % cvs -q update -r checkpoint52i_post -d -P
+ \end{verbatim}
+ This will update the ``tag'' to ``checkpoint52i\_post'', add any new
+ directories (-d) and remove any empty directories (-P). The -q option
+ means be quiet which will reduce the number of messages you'll see in
+ the terminal. If you have modified the code prior to upgrading, CVS
+ will try to merge your changes with the upgrades. If there is a
+ conflict between your modifications and the upgrade, it will report
+ that file with a ``C'' in front, e.g.:
+ \begin{verbatim}
+ C model/src/ini_parms.F
+ \end{verbatim}
+ If the list of conflicts scrolled off the screen, you can re-issue the
+ cvs update command and it will report the conflicts. Conflicts are
+ indicated in the code by the delimites ``$<<<<<<<$'', ``======='' and
+ ``$>>>>>>>$''. For example,
+ {\small
+ \begin{verbatim}
+ <<<<<<< ini_parms.F
+      & bottomDragLinear,myOwnBottomDragCoefficient,
+ =======
+      & bottomDragLinear,bottomDragQuadratic,
+ >>>>>>> 1.18
+ \end{verbatim}
+ }
+ means that you added ``myOwnBottomDragCoefficient'' to a namelist at
+ the same time and place that we added ``bottomDragQuadratic''. You
+ need to resolve this conflict and in this case the line should be
+ changed to:
+ {\small
+ \begin{verbatim}
+      & bottomDragLinear,bottomDragQuadratic,myOwnBottomDragCoefficient,
+ \end{verbatim}
+ }
+ and the lines with the delimiters ($<<<<<<$,======,$>>>>>>$) be deleted.
+ Unless you are making modifications which exactly parallel
+ developments we make, these types of conflicts should be rare.
+ \paragraph*{Upgrading to the current pre-release version}
+ We don't make a ``release'' for every little patch and bug fix in
+ order to keep the frequency of upgrades to a minimum. However, if you
+ have run into a problem for which ``we have already fixed in the
+ latest code'' and we haven't made a ``tag'' or ``release'' since that
+ patch then you'll need to get the latest code:
+ \begin{verbatim}
+ % cvs -q update -A -d -P
+ \end{verbatim}
+ Unlike, the ``check-out'' and ``update'' procedures above, there is no
+ ``tag'' or release name. The -A tells CVS to upgrade to the
+ very latest version. As a rule, we don't recommend this since you
+ might upgrade while we are in the processes of checking in the code so
+ that you may only have part of a patch. Using this method of updating
+ also means we can't tell what version of the code you are working
+ with. So please be sure you understand what you're doing.
+ \subsection{Method 2 - Tar file download}
+ \label{sec:conventionalDownload}
+ If you do not have CVS on your system, you can download the model as a
+ tar file from the web site at:
+ \begin{rawhtml} <A href=http://mitgcm.org/download/ target="idontexist"> \end{rawhtml}
  \begin{verbatim}
  http://mitgcm.org/download/
  \end{verbatim}
+ \begin{rawhtml} </A> \end{rawhtml}
+ The tar file still contains CVS information which we urge you not to
+ delete; even if you do not use CVS yourself the information can help
+ us if you should need to send us your copy of the code.  If a recent
+ tar file does not exist, then please contact the developers through
+ the
+ \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
+ MITgcm-support@mitgcm.org
+ \begin{rawhtml} </A> \end{rawhtml}
+ mailing list.
+ \section{Model and directory structure}
+ \begin{rawhtml}
+ <!-- CMIREDIR:directory_structure: -->
+ \end{rawhtml}
+ The ``numerical'' model is contained within a execution environment
+ support wrapper. This wrapper is designed to provide a general
+ framework for grid-point models. MITgcmUV is a specific numerical
+ model that uses the framework. Under this structure the model is split
+ into execution environment support code and conventional numerical
+ model code. The execution environment support code is held under the
+ \texttt{eesupp} directory. The grid point model code is held under the
+ \texttt{model} directory. Code execution actually starts in the
+ \texttt{eesupp} routines and not in the \texttt{model} routines. For
+ this reason the top-level \texttt{MAIN.F} is in the
+ \texttt{eesupp/src} directory. In general, end-users should not need
+ to worry about this level. The top-level routine for the numerical
+ part of the code is in \texttt{model/src/THE\_MODEL\_MAIN.F}. Here is
+ a brief description of the directory structure of the model under the
+ root tree (a detailed description is given in section 3: Code
+ structure).
+ \begin{itemize}
+ \item \texttt{doc}: contains brief documentation notes.
+ \item \texttt{eesupp}: contains the execution environment source code.
+   Also subdivided into two subdirectories \texttt{inc} and
+   \texttt{src}.
+ \item \texttt{model}: this directory contains the main source code.
+   Also subdivided into two subdirectories \texttt{inc} and
+   \texttt{src}.
+ \item \texttt{pkg}: contains the source code for the packages. Each
+   package corresponds to a subdirectory. For example, \texttt{gmredi}
+   contains the code related to the Gent-McWilliams/Redi scheme,
+   \texttt{aim} the code relative to the atmospheric intermediate
+   physics. The packages are described in detail in chapter \ref{chap:packagesI}.
+ \item \texttt{tools}: this directory contains various useful tools.
+   For example, \texttt{genmake2} is a script written in csh (C-shell)
+   that should be used to generate your makefile. The directory
+   \texttt{adjoint} contains the makefile specific to the Tangent
+   linear and Adjoint Compiler (TAMC) that generates the adjoint code.
+   The latter is described in detail in part \ref{chap.ecco}.
+   This directory also contains the subdirectory build\_options, which
+   contains the `optfiles' with the compiler options for the different
+   compilers and machines that can run MITgcm.
+ \item \texttt{utils}: this directory contains various utilities. The
+   subdirectory \texttt{knudsen2} contains code and a makefile that
+   compute coefficients of the polynomial approximation to the knudsen
+   formula for an ocean nonlinear equation of state. The
+   \texttt{matlab} subdirectory contains matlab scripts for reading
+   model output directly into matlab. \texttt{scripts} contains C-shell
+   post-processing scripts for joining processor-based and tiled-based
+   model output. The subdirectory exch2 contains the code needed for
+   the exch2 package to work with different combinations of domain
+   decompositions.
+ \item \texttt{verification}: this directory contains the model
+   examples. See section \ref{sec:modelExamples}.
+ \item \texttt{jobs}: contains sample job scripts for running MITgcm.
+ \item \texttt{lsopt}: Line search code used for optimization.
+ \item \texttt{optim}: Interface between MITgcm and line search code.
+ \end{itemize}
+ \section[Building MITgcm]{Building the code}
+ \label{sec:buildingCode}
+ \begin{rawhtml}
+ <!-- CMIREDIR:buildingCode: -->
+ \end{rawhtml}
+ To compile the code, we use the \texttt{make} program. This uses a
+ file (\texttt{Makefile}) that allows us to pre-process source files,
+ specify compiler and optimization options and also figures out any
+ file dependencies. We supply a script (\texttt{genmake2}), described
+ in section \ref{sec:genmake}, that automatically creates the
+ \texttt{Makefile} for you. You then need to build the dependencies and
+ compile the code.
+ As an example, assume that you want to build and run experiment
+ \texttt{verification/exp2}. The are multiple ways and places to
+ actually do this but here let's build the code in
+ \texttt{verification/exp2/build}:
+ \begin{verbatim}
+ % cd verification/exp2/build
+ \end{verbatim}
+ First, build the \texttt{Makefile}:
+ \begin{verbatim}
+ % ../../../tools/genmake2 -mods=../code
+ \end{verbatim}
+ The command line option tells \texttt{genmake} to override model source
+ code with any files in the directory \texttt{../code/}.
+ On many systems, the \texttt{genmake2} program will be able to
+ automatically recognize the hardware, find compilers and other tools
+ within the user's path (``\texttt{echo \$PATH}''), and then choose an
+ appropriate set of options from the files (``optfiles'') contained in
+ the \texttt{tools/build\_options} directory.  Under some
+ circumstances, a user may have to create a new ``optfile'' in order to
+ specify the exact combination of compiler, compiler flags, libraries,
+ and other options necessary to build a particular configuration of
+ MITgcm.  In such cases, it is generally helpful to read the existing
+ ``optfiles'' and mimic their syntax.
+ Through the MITgcm-support list, the MITgcm developers are willing to
+ provide help writing or modifing ``optfiles''.  And we encourage users
+ to post new ``optfiles'' (particularly ones for new machines or
+ architectures) to the
+ \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
+ MITgcm-support@mitgcm.org
+ \begin{rawhtml} </A> \end{rawhtml}
+ list.
- \subsection{Model and directory structure}
+ To specify an optfile to \texttt{genmake2}, the syntax is:
+ \begin{verbatim}
- The ``numerical'' model is contained within a execution environment support
+ % ../../../tools/genmake2 -mods=../code -of /path/to/optfile
- wrapper. This wrapper is designed to provide a general framework for
+ \end{verbatim}
- grid-point models. MITgcmUV is a specific numerical model that uses the
- framework. Under this structure the model is split into execution
- environment support code and conventional numerical model code. The
- execution environment support code is held under the \textit{eesupp}
- directory. The grid point model code is held under the \textit{model}
- directory. Code execution actually starts in the \textit{eesupp} routines
- and not in the \textit{model} routines. For this reason the top-level
- \textit{MAIN.F} is in the \textit{eesupp/src} directory. In general,
- end-users should not need to worry about this level. The top-level routine
- for the numerical part of the code is in \textit{model/src/THE\_MODEL\_MAIN.F%
- }. Here is a brief description of the directory structure of the model under
- the root tree (a detailed description is given in section 3: Code structure).
- \begin{itemize}
- \item \textit{bin}: this directory is initially empty. It is the default
- directory in which to compile the code.
- \item \textit{diags}: contains the code relative to time-averaged
- diagnostics. It is subdivided into two subdirectories \textit{inc} and
- \textit{src} that contain include files (*.\textit{h} files) and fortran
- subroutines (*.\textit{F} files), respectively.
- \item \textit{doc}: contains brief documentation notes.
- \item \textit{eesupp}: contains the execution environment source code. Also
- subdivided into two subdirectories \textit{inc} and \textit{src}.
- \item \textit{exe}: this directory is initially empty. It is the default
- directory in which to execute the code.
- \item \textit{model}: this directory contains the main source code. Also
- subdivided into two subdirectories \textit{inc} and \textit{src}.
- \item \textit{pkg}: contains the source code for the packages. Each package
- corresponds to a subdirectory. For example, \textit{gmredi} contains the
- code related to the Gent-McWilliams/Redi scheme, \textit{aim} the code
- relative to the atmospheric intermediate physics. The packages are described
- in detail in section 3.
- \item \textit{tools}: this directory contains various useful tools. For
- example, \textit{genmake} is a script written in csh (C-shell) that should
- be used to generate your makefile. The directory \textit{adjoint} contains
- the makefile specific to the Tangent linear and Adjoint Compiler (TAMC) that
- generates the adjoint code. The latter is described in details in part V.
- \item \textit{utils}: this directory contains various utilities. The
- subdirectory \textit{knudsen2} contains code and a makefile that compute
- coefficients of the polynomial approximation to the knudsen formula for an
- ocean nonlinear equation of state. The \textit{matlab} subdirectory contains
- matlab scripts for reading model output directly into matlab. \textit{scripts%
- } contains C-shell post-processing scripts for joining processor-based and
- tiled-based model output.
- \item \textit{verification}: this directory contains the model examples. See
- below.
- \end{itemize}
- \subsection{Model examples}
- Now that you have successfully downloaded the model code we recommend that
- you first try to run the examples provided with the base version. You will
- probably want to run the example that is the closest to the configuration
- you will use eventually. The examples are located in subdirectories under
- the directory \textit{verification} and are briefly described below (a full
- description is given in section 2):
- \subsubsection{List of model examples}
- \begin{itemize}
- \item \textit{exp0} - single layer, ocean double gyre (barotropic with
- free-surface).
- \item \textit{exp1} - 4 layers, ocean double gyre.
- \item \textit{exp2} - 4x4 degree global ocean simulation with steady
- climatological forcing.
- \item \textit{exp4} - flow over a Gaussian bump in open-water or channel
- with open boundaries.
- \item \textit{exp5} - inhomogenously forced ocean convection in a doubly
- periodic box.
- \item \textit{front\_relax} - relaxation of an ocean thermal front (test for
- Gent/McWilliams scheme). 2D (Y-Z).
- \item \textit{internal wave} - ocean internal wave forced by open boundary
- conditions.
- \item \textit{natl\_box} - eastern subtropical North Atlantic with KPP
- scheme; 1 month integration
- \item \textit{hs94.1x64x5} - zonal averaged atmosphere using Held and Suarez
- '94 forcing.
- \item \textit{hs94.128x64x5} - 3D atmosphere dynamics using Held and Suarez
- '94 forcing.
- \item \textit{hs94.cs-32x32x5} - 3D atmosphere dynamics using Held and
- Suarez '94 forcing on the cubed sphere.
- \item \textit{aim.5l\_zon-ave} - Intermediate Atmospheric physics, 5 layers
- Molteni physics package. Global Zonal Mean configuration, 1x64x5 resolution.
- \item \textit{aim.5l\_XZ\_Equatorial\_Slice} - Intermediate Atmospheric
- physics, 5 layers Molteni physics package. Equatorial Slice configuration.
-D (X-Z).
- \item \textit{aim.5l\_Equatorial\_Channel} - Intermediate Atmospheric
- physics, 5 layers Molteni physics package. 3D Equatorial Channel
- configuration (not completely tested).
- \item \textit{aim.5l\_LatLon} - Intermediate Atmospheric physics, 5 layers
- Molteni physics package. Global configuration, 128x64x5 resolution.
- \item \textit{adjustment.128x64x1}
- \item \textit{adjustment.cs-32x32x1}
- \end{itemize}
- \subsubsection{Directory structure of model examples}
- Each example directory has the following subdirectories:
- \begin{itemize}
- \item \textit{code}: contains the code particular to the example. At a
- minimum, this directory includes the following files:
- \begin{itemize}
- \item \textit{code/CPP\_EEOPTIONS.h}: declares CPP keys relative to the
- ``execution environment'' part of the code. The default version is located
- in \textit{eesupp/inc}.
- \item \textit{code/CPP\_OPTIONS.h}: declares CPP keys relative to the
- ``numerical model'' part of the code. The default version is located in
- \textit{model/inc}.
- \item \textit{code/SIZE.h}: declares size of underlying computational grid.
- The default version is located in \textit{model/inc}.
- \end{itemize}
- In addition, other include files and subroutines might be present in \textit{%
- code} depending on the particular experiment. See section 2 for more details.
- \item \textit{input}: contains the input data files required to run the
- example. At a mimimum, the \textit{input} directory contains the following
- files:
- \begin{itemize}
- \item \textit{input/data}: this file, written as a namelist, specifies the
- main parameters for the experiment.
- \item \textit{input/data.pkg}: contains parameters relative to the packages
- used in the experiment.
- \item \textit{input/eedata}: this file contains ``execution environment''
- data. At present, this consists of a specification of the number of threads
- to use in $X$ and $Y$ under multithreaded execution.
- \end{itemize}
- In addition, you will also find in this directory the forcing and topography
- files as well as the files describing the initial state of the experiment.
- This varies from experiment to experiment. See section 2 for more details.
- \item \textit{results}: this directory contains the output file \textit{%
- output.txt} produced by the simulation example. This file is useful for
- comparison with your own output when you run the experiment.
- \end{itemize}
- Once you have chosen the example you want to run, you are ready to compile
- the code.
- \subsection{Compiling the code}
- \subsubsection{The script \textit{genmake}}
- To compile the code, use the script \textit{genmake} located in the \textit{%
- tools} directory. \textit{genmake} is a script that generates the makefile.
- It has been written so that the code can be compiled on a wide diversity of
- machines and systems. However, if it doesn't work the first time on your
- platform, you might need to edit certain lines of \textit{genmake} in the
- section containing the setups for the different machines. The file is
- structured like this:
- \begin{verbatim}
-         .
-         .
-         .
- general instructions (machine independent)
-         .
-         .
-         .
-     - setup machine 1
-     - setup machine 2
-     - setup machine 3
-     - setup machine 4
-        etc
-         .
-         .
-         .
- \end{verbatim}
- For example, the setup corresponding to a DEC alpha machine is reproduced
- here:
- \begin{verbatim}
-   case OSF1+mpi:
-     echo "Configuring for DEC Alpha"
-     set CPP        = ( '/usr/bin/cpp -P' )
-     set DEFINES    = ( ${DEFINES}  '-DTARGET_DEC -DWORDLENGTH=1' )
-     set KPP        = ( 'kapf' )
-     set KPPFILES   = ( 'main.F' )
-     set KFLAGS1    = ( '-scan=132 -noconc -cmp=' )
-     set FC         = ( 'f77' )
-     set FFLAGS     = ( '-convert big_endian -r8 -extend_source -automatic -call_shared -notransform_loops -align dcommons' )
-     set FOPTIM     = ( '-O5 -fast -tune host -inline all' )
-     set NOOPTFLAGS = ( '-O0' )
-     set LIBS       = ( '-lfmpi -lmpi -lkmp_osfp10 -pthread' )
-     set NOOPTFILES = ( 'barrier.F different_multiple.F external_fields_load.F')
-     set RMFILES    = ( '*.p.out' )
-     breaksw
- \end{verbatim}
- Typically, these are the lines that you might need to edit to make \textit{%
- genmake} work on your platform if it doesn't work the first time. \textit{%
- genmake} understands several options that are described here:
- \begin{itemize}
- \item -rootdir=dir
- indicates where the model root directory is relative to the directory where
- you are compiling. This option is not needed if you compile in the \textit{%
- bin} directory (which is the default compilation directory) or within the
- \textit{verification} tree.
- \item -mods=dir1,dir2,...
- indicates the relative or absolute paths directories where the sources
- should take precedence over the default versions (located in \textit{model},
- \textit{eesupp},...). Typically, this option is used when running the
- examples, see below.
- \item -enable=pkg1,pkg2,...
- enables packages source code \textit{pkg1}, \textit{pkg2},... when creating
- the makefile.
- \item -disable=pkg1,pkg2,...
- disables packages source code \textit{pkg1}, \textit{pkg2},... when creating
+ Once a \texttt{Makefile} has been generated, we create the
- the makefile.
+ dependencies with the command:
+ \begin{verbatim}
+ % make depend
+ \end{verbatim}
+ This modifies the \texttt{Makefile} by attaching a (usually, long)
+ list of files upon which other files depend. The purpose of this is to
+ reduce re-compilation if and when you start to modify the code. The
+ {\tt make depend} command also creates links from the model source to
+ this directory.  It is important to note that the {\tt make depend}
+ stage will occasionally produce warnings or errors since the
+ dependency parsing tool is unable to find all of the necessary header
+ files (\textit{eg.}  \texttt{netcdf.inc}).  In these circumstances, it
+ is usually OK to ignore the warnings/errors and proceed to the next
+ step.
- \item -platform=machine
+ Next one can compile the code using:
+ \begin{verbatim}
+ % make
+ \end{verbatim}
+ The {\tt make} command creates an executable called \texttt{mitgcmuv}.
+ Additional make ``targets'' are defined within the makefile to aid in
+ the production of adjoint and other versions of MITgcm.  On SMP
+ (shared multi-processor) systems, the build process can often be sped
+ up appreciably using the command:
+ \begin{verbatim}
+ % make -j 2
+ \end{verbatim}
+ where the ``2'' can be replaced with a number that corresponds to the
+ number of CPUs available.
- specifies the platform for which you want the makefile. In general, you
+ Now you are ready to run the model. General instructions for doing so are
- won't need this option. \textit{genmake} will select the right machine for
+ given in section \ref{sec:runModel}. Here, we can run the model by
- you (the one you're working on!). However, this option is useful if you have
+ first creating links to all the input files:
- a choice of several compilers on one machine and you want to use the one
+ \begin{verbatim}
- that is not the default (ex: \texttt{pgf77} instead of \texttt{f77} under
+ ln -s ../input/* .
- Linux).
+ \end{verbatim}
+ and then calling the executable with:
+ \begin{verbatim}
+ ./mitgcmuv > output.txt
+ \end{verbatim}
+ where we are re-directing the stream of text output to the file
+ \texttt{output.txt}.
- \item -mpi
+ \subsection{Building/compiling the code elsewhere}
- this is used when you want to run the model in parallel processing mode
+ In the example above (section \ref{sec:buildingCode}) we built the
- under mpi (see section on parallel computation for more details).
+ executable in the {\em input} directory of the experiment for
+ convenience. You can also configure and compile the code in other
+ locations, for example on a scratch disk with out having to copy the
+ entire source tree. The only requirement to do so is you have {\tt
+   genmake2} in your path or you know the absolute path to {\tt
+   genmake2}.
- \item -jam
+ The following sections outline some possible methods of organizing
+ your source and data.
- this is used when you want to run the model in parallel processing mode
+ \subsubsection{Building from the {\em ../code directory}}
- under jam (see section on parallel computation for more details).
- \end{itemize}
- For some of the examples, there is a file called \textit{.genmakerc} in the
+ This is just as simple as building in the {\em input/} directory:
- \textit{input} directory that has the relevant \textit{genmake} options for
- that particular example. In this way you don't need to type the options when
- invoking \textit{genmake}.
- \subsubsection{Compiling}
- Let's assume that you want to run, say, example \textit{exp2} in the \textit{%
- input} directory. To compile the code, type the following commands from the
- model root tree:
  \begin{verbatim}
- % cd verification/exp2/input
+ % cd verification/exp2/code
- % ../../../tools/genmake
+ % ../../../tools/genmake2
  % make depend
  % make
  \end{verbatim}
+ However, to run the model the executable ({\em mitgcmuv}) and input
- If there is no \textit{.genmakerc} in the \textit{input} directory, you have
+ files must be in the same place. If you only have one calculation to make:
- to use the following options when invoking \textit{genmake}:
  \begin{verbatim}
- % ../../../tools/genmake  -mods=../code
+ % cd ../input
+ % cp ../code/mitgcmuv ./
+ % ./mitgcmuv > output.txt
  \end{verbatim}
+ or if you will be making multiple runs with the same executable:
- In addition, you will probably want to disable some of the packages. Taking
- again the case of \textit{exp2}, the full \textit{genmake} command will
- probably look like this:
  \begin{verbatim}
- % ../../../tools/genmake  -mods=../code  -disable=kpp,gmredi,aim,...
+ % cd ../
+ % cp -r input run1
+ % cp code/mitgcmuv run1
+ % cd run1
+ % ./mitgcmuv > output.txt
  \end{verbatim}
- The make command creates an executable called \textit{mitgcmuv}.
+ \subsubsection{Building from a new directory}
- Note that you can compile and run the code in another directory than \textit{%
+ Since the {\em input} directory contains input files it is often more
- input}. You just need to make sure that you copy the input data files into
+ useful to keep {\em input} pristine and build in a new directory
- the directory where you want to run the model. For example to compile from
+ within {\em verification/exp2/}:
- \textit{code}:
  \begin{verbatim}
- % cd verification/exp2/code
+ % cd verification/exp2
- % ../../../tools/genmake
+ % mkdir build
+ % cd build
+ % ../../../tools/genmake2 -mods=../code
  % make depend
  % make
  \end{verbatim}
+ This builds the code exactly as before but this time you need to copy
+ either the executable or the input files or both in order to run the
+ model. For example,
+ \begin{verbatim}
+ % cp ../input/* ./
+ % ./mitgcmuv > output.txt
+ \end{verbatim}
+ or if you tend to make multiple runs with the same executable then
+ running in a new directory each time might be more appropriate:
+ \begin{verbatim}
+ % cd ../
+ % mkdir run1
+ % cp build/mitgcmuv run1/
+ % cp input/* run1/
+ % cd run1
+ % ./mitgcmuv > output.txt
+ \end{verbatim}
+ \subsubsection{Building on a scratch disk}
+ Model object files and output data can use up large amounts of disk
+ space so it is often the case that you will be operating on a large
+ scratch disk. Assuming the model source is in {\em ~/MITgcm} then the
+ following commands will build the model in {\em /scratch/exp2-run1}:
+ \begin{verbatim}
+ % cd /scratch/exp2-run1
+ % ~/MITgcm/tools/genmake2 -rootdir=~/MITgcm \
+   -mods=~/MITgcm/verification/exp2/code
+ % make depend
+ % make
+ \end{verbatim}
+ To run the model here, you'll need the input files:
+ \begin{verbatim}
+ % cp ~/MITgcm/verification/exp2/input/* ./
+ % ./mitgcmuv > output.txt
+ \end{verbatim}
- \subsection{Running the model}
+ As before, you could build in one directory and make multiple runs of
+ the one experiment:
- The first thing to do is to run the code by typing \textit{mitgcmuv} and see
+ \begin{verbatim}
- what happens. You can compare what you get with what is in the \textit{%
+ % cd /scratch/exp2
- results} directory. Unless noted otherwise, most examples are set up to run
+ % mkdir build
- for a few time steps only so that you can quickly figure out whether the
+ % cd build
- model is working or not.
+ % ~/MITgcm/tools/genmake2 -rootdir=~/MITgcm \
+   -mods=~/MITgcm/verification/exp2/code
- \subsubsection{Output files}
+ % make depend
+ % make
- The model produces various output files. At a minimum, the instantaneous
+ % cd ../
- ``state'' of the model is written out, which is made of the following files:
+ % cp -r ~/MITgcm/verification/exp2/input run2
+ % cd run2
- \begin{itemize}
+ % ./mitgcmuv > output.txt
- \item \textit{U.00000nIter} - zonal component of velocity field (m/s and $>
+ \end{verbatim}
-$ eastward).
- \item \textit{V.00000nIter} - meridional component of velocity field (m/s
- and $> 0$ northward).
- \item \textit{W.00000nIter} - vertical component of velocity field (ocean:
- m/s and $> 0$ upward, atmosphere: Pa/s and $> 0$ towards increasing pressure
- i.e. downward).
- \item \textit{T.00000nIter} - potential temperature (ocean: $^{0}$C,
- atmosphere: $^{0}$K).
- \item \textit{S.00000nIter} - ocean: salinity (psu), atmosphere: water vapor
+ \subsection{Using \texttt{genmake2}}
- (g/kg).
+ \label{sec:genmake}
+ To compile the code, first use the program \texttt{genmake2} (located
+ in the \texttt{tools} directory) to generate a Makefile.
+ \texttt{genmake2} is a shell script written to work with all
+ ``sh''--compatible shells including bash v1, bash v2, and Bourne.
+ %Internally, \texttt{genmake2} determines the locations of needed
+ %files, the compiler, compiler options, libraries, and Unix tools.  It
+ %relies upon a number of ``optfiles'' located in the
+ %\texttt{tools/build\_options} directory.
+ \texttt{genmake2} parses information from the following sources:
+ \begin{description}
+ \item[-] a {\em gemake\_local} file if one is found in the current
+   directory
+ \item[-] command-line options
+ \item[-] an "options file" as specified by the command-line option
+   \texttt{--optfile=/PATH/FILENAME}
+ \item[-] a {\em packages.conf} file (if one is found) with the
+   specific list of packages to compile. The search path for
+   file {\em packages.conf} is, first, the current directory and
+   then each of the "MODS" directories in the given order (see below).
+ \end{description}
+ \subsubsection{Optfiles in \texttt{tools/build\_options} directory:}
+ The purpose of the optfiles is to provide all the compilation options
+ for particular ``platforms'' (where ``platform'' roughly means the
+ combination of the hardware and the compiler) and code configurations.
+ Given the combinations of possible compilers and library dependencies
+ ({\it eg.}  MPI and NetCDF) there may be numerous optfiles available
+ for a single machine.  The naming scheme for the majority of the
+ optfiles shipped with the code is
+ \begin{center}
+   {\bf OS\_HARDWARE\_COMPILER }
+ \end{center}
+ where
+ \begin{description}
+ \item[OS] is the name of the operating system (generally the
+   lower-case output of the {\tt 'uname'} command)
+ \item[HARDWARE] is a string that describes the CPU type and
+   corresponds to output from the  {\tt 'uname -m'} command:
+   \begin{description}
+   \item[ia32] is for ``x86'' machines such as i386, i486, i586, i686,
+     and athlon
+   \item[ia64] is for Intel IA64 systems (eg. Itanium, Itanium2)
+   \item[amd64] is AMD x86\_64 systems
+   \item[ppc] is for Mac PowerPC systems
+   \end{description}
+ \item[COMPILER] is the compiler name (generally, the name of the
+   FORTRAN executable)
+ \end{description}
+ In many cases, the default optfiles are sufficient and will result in
+ usable Makefiles.  However, for some machines or code configurations,
+ new ``optfiles'' must be written. To create a new optfile, it is
+ generally best to start with one of the defaults and modify it to suit
+ your needs.  Like \texttt{genmake2}, the optfiles are all written
+ using a simple ``sh''--compatible syntax.  While nearly all variables
+ used within \texttt{genmake2} may be specified in the optfiles, the
+ critical ones that should be defined are:
+ \begin{description}
+ \item[FC] the FORTRAN compiler (executable) to use
+ \item[DEFINES] the command-line DEFINE options passed to the compiler
+ \item[CPP] the C pre-processor to use
+ \item[NOOPTFLAGS] options flags for special files that should not be
+   optimized
+ \end{description}
+ For example, the optfile for a typical Red Hat Linux machine (``ia32''
+ architecture) using the GCC (g77) compiler is
+ \begin{verbatim}
+ FC=g77
+ DEFINES='-D_BYTESWAPIO -DWORDLENGTH=4'
+ CPP='cpp  -traditional -P'
+ NOOPTFLAGS='-O0'
+ #  For IEEE, use the "-ffloat-store" option
+ if test "x$IEEE" = x ; then
+     FFLAGS='-Wimplicit -Wunused -Wuninitialized'
+     FOPTIM='-O3 -malign-double -funroll-loops'
+ else
+     FFLAGS='-Wimplicit -Wunused -ffloat-store'
+     FOPTIM='-O0 -malign-double'
+ fi
+ \end{verbatim}
+ If you write an optfile for an unrepresented machine or compiler, you
+ are strongly encouraged to submit the optfile to the MITgcm project
+ for inclusion.  Please send the file to the
+ \begin{rawhtml} <A href="mail-to:MITgcm-support@mitgcm.org"> \end{rawhtml}
+ \begin{center}
+   MITgcm-support@mitgcm.org
+ \end{center}
+ \begin{rawhtml} </A> \end{rawhtml}
+ mailing list.
- \item \textit{Eta.00000nIter} - ocean: surface elevation (m), atmosphere:
+ \subsubsection{Command-line options:}
- surface pressure anomaly (Pa).
- \end{itemize}
- The chain \textit{00000nIter} consists of ten figures that specify the
+ In addition to the optfiles, \texttt{genmake2} supports a number of
- iteration number at which the output is written out. For example, \textit{%
+ helpful command-line options.  A complete list of these options can be
- U.0000000300} is the zonal velocity at iteration 300.
+ obtained from:
+ \begin{verbatim}
+ % genmake2 -h
+ \end{verbatim}
+ The most important command-line options are:
+ \begin{description}
+ \item[\texttt{--optfile=/PATH/FILENAME}] specifies the optfile that
+   should be used for a particular build.
+   If no "optfile" is specified (either through the command line or the
+   MITGCM\_OPTFILE environment variable), genmake2 will try to make a
+   reasonable guess from the list provided in {\em
+     tools/build\_options}.  The method used for making this guess is
+   to first determine the combination of operating system and hardware
+   (eg. "linux\_ia32") and then find a working FORTRAN compiler within
+   the user's path.  When these three items have been identified,
+   genmake2 will try to find an optfile that has a matching name.
+ \item[\texttt{--mods='DIR1 DIR2 DIR3 ...'}] specifies a list of
+   directories containing ``modifications''.  These directories contain
+   files with names that may (or may not) exist in the main MITgcm
+   source tree but will be overridden by any identically-named sources
+   within the ``MODS'' directories.
+   The order of precedence for this "name-hiding" is as follows:
+   \begin{itemize}
+   \item ``MODS'' directories (in the order given)
+   \item Packages either explicitly specified or provided by default
+     (in the order given)
+   \item Packages included due to package dependencies (in the order
+     that that package dependencies are parsed)
+   \item The "standard dirs" (which may have been specified by the
+     ``-standarddirs'' option)
+   \end{itemize}
+ \item[\texttt{--pgroups=/PATH/FILENAME}] specifies the file
+   where package groups are defined. If not set, the package-groups
+   definition will be read from {\em pkg/pkg\_groups}.
+   It also contains the default list of packages (defined
+   as the group ``{\it default\_pkg\_list}'' which is used
+   when no specific package list ({\em packages.conf})
+   is found in current directory or in any "MODS" directory.
+ \item[\texttt{--pdepend=/PATH/FILENAME}] specifies the dependency file
+   used for packages.
+   If not specified, the default dependency file {\em pkg/pkg\_depend}
+   is used.  The syntax for this file is parsed on a line-by-line basis
+   where each line containes either a comment ("\#") or a simple
+   "PKGNAME1 (+|-)PKGNAME2" pairwise rule where the "+" or "-" symbol
+   specifies a "must be used with" or a "must not be used with"
+   relationship, respectively.  If no rule is specified, then it is
+   assumed that the two packages are compatible and will function
+   either with or without each other.
+ \item[\texttt{--adof=/path/to/file}] specifies the "adjoint" or
+   automatic differentiation options file to be used.  The file is
+   analogous to the ``optfile'' defined above but it specifies
+   information for the AD build process.
+   The default file is located in {\em
+     tools/adjoint\_options/adjoint\_default} and it defines the "TAF"
+   and "TAMC" compilers.  An alternate version is also available at
+   {\em tools/adjoint\_options/adjoint\_staf} that selects the newer
+   "STAF" compiler.  As with any compilers, it is helpful to have their
+   directories listed in your {\tt \$PATH} environment variable.
+ \item[\texttt{--mpi}] This option enables certain MPI features (using
+   CPP \texttt{\#define}s) within the code and is necessary for MPI
+   builds (see Section \ref{sec:mpi-build}).
+ \item[\texttt{--make=/path/to/gmake}] Due to the poor handling of
+   soft-links and other bugs common with the \texttt{make} versions
+   provided by commercial Unix vendors, GNU \texttt{make} (sometimes
+   called \texttt{gmake}) should be preferred.  This option provides a
+   means for specifying the make executable to be used.
+ \item[\texttt{--bash=/path/to/sh}] On some (usually older UNIX)
+   machines, the ``bash'' shell is unavailable.  To run on these
+   systems, \texttt{genmake2} can be invoked using an ``sh'' (that is,
+   a Bourne, POSIX, or compatible) shell.  The syntax in these
+   circumstances is:
+   \begin{center}
+     \texttt{\%  /bin/sh genmake2 -bash=/bin/sh [...options...]}
+   \end{center}
+   where \texttt{/bin/sh} can be replaced with the full path and name
+   of the desired shell.
+ \end{description}
+ \subsection{Building with MPI}
+ \label{sec:mpi-build}
+ Building MITgcm to use MPI libraries can be complicated due to the
+ variety of different MPI implementations available, their dependencies
+ or interactions with different compilers, and their often ad-hoc
+ locations within file systems.  For these reasons, its generally a
+ good idea to start by finding and reading the documentation for your
+ machine(s) and, if necessary, seeking help from your local systems
+ administrator.
+ The steps for building MITgcm with MPI support are:
+ \begin{enumerate}
+ \item Determine the locations of your MPI-enabled compiler and/or MPI
+   libraries and put them into an options file as described in Section
+   \ref{sec:genmake}.  One can start with one of the examples in:
+   \begin{rawhtml} <A
+     href="http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/build_options/">
+   \end{rawhtml}
+   \begin{center}
+     \texttt{MITgcm/tools/build\_options/}
+   \end{center}
+   \begin{rawhtml} </A> \end{rawhtml}
+   such as \texttt{linux\_ia32\_g77+mpi\_cg01} or
+   \texttt{linux\_ia64\_efc+mpi} and then edit it to suit the machine at
+   hand.  You may need help from your user guide or local systems
+   administrator to determine the exact location of the MPI libraries.
+   If libraries are not installed, MPI implementations and related
+   tools are available including:
+   \begin{itemize}
+   \item \begin{rawhtml} <A
+       href="http://www-unix.mcs.anl.gov/mpi/mpich/">
+     \end{rawhtml}
+     MPICH
+     \begin{rawhtml} </A> \end{rawhtml}
+   \item \begin{rawhtml} <A
+       href="http://www.lam-mpi.org/">
+     \end{rawhtml}
+     LAM/MPI
+     \begin{rawhtml} </A> \end{rawhtml}
+   \item \begin{rawhtml} <A
+       href="http://www.osc.edu/~pw/mpiexec/">
+     \end{rawhtml}
+     MPIexec
+     \begin{rawhtml} </A> \end{rawhtml}
+   \end{itemize}
+ \item Build the code with the \texttt{genmake2} \texttt{-mpi} option
+   (see Section \ref{sec:genmake}) using commands such as:
+ {\footnotesize \begin{verbatim}
+   %  ../../../tools/genmake2 -mods=../code -mpi -of=YOUR_OPTFILE
+   %  make depend
+   %  make
+ \end{verbatim} }
+ \item Run the code with the appropriate MPI ``run'' or ``exec''
+   program provided with your particular implementation of MPI.
+   Typical MPI packages such as MPICH will use something like:
+ \begin{verbatim}
+   %  mpirun -np 4 -machinefile mf ./mitgcmuv
+ \end{verbatim}
+   Sightly more complicated scripts may be needed for many machines
+   since execution of the code may be controlled by both the MPI
+   library and a job scheduling and queueing system such as PBS,
+   LoadLeveller, Condor, or any of a number of similar tools.  A few
+   example scripts (those used for our \begin{rawhtml} <A
+     href="http://mitgcm.org/public/testing.html"> \end{rawhtml}regular
+   verification runs\begin{rawhtml} </A> \end{rawhtml}) are available
+   at:
+   \begin{rawhtml} <A
+     href="http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/example_scripts/">
+   \end{rawhtml}
+   {\footnotesize \tt
+     http://mitgcm.org/viewvc/MITgcm/MITgcm/tools/example\_scripts/ }
+   \begin{rawhtml} </A> \end{rawhtml}
+   or at:
+   \begin{rawhtml} <A
+     href="http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/test_scripts/">
+   \end{rawhtml}
+   {\footnotesize \tt
+     http://mitgcm.org/viewvc/MITgcm/MITgcm\_contrib/test\_scripts/ }
+   \begin{rawhtml} </A> \end{rawhtml}
+ \end{enumerate}
+ An example of the above process on the MITgcm cluster (``cg01'') using
+ the GNU g77 compiler and the mpich MPI library is:
+ {\footnotesize \begin{verbatim}
+   %  cd MITgcm/verification/exp5
+   %  mkdir build
+   %  cd build
+   %  ../../../tools/genmake2 -mpi -mods=../code \
+        -of=../../../tools/build_options/linux_ia32_g77+mpi_cg01
+   %  make depend
+   %  make
+   %  cd ../input
+   %  /usr/local/pkg/mpi/mpi-1.2.4..8a-gm-1.5/g77/bin/mpirun.ch_gm \
+        -machinefile mf --gm-kill 5 -v -np 2  ../build/mitgcmuv
+ \end{verbatim} }
+ \section[Running MITgcm]{Running the model in prognostic mode}
+ \label{sec:runModel}
+ \begin{rawhtml}
+ <!-- CMIREDIR:runModel: -->
+ \end{rawhtml}
+ If compilation finished succesfully (section \ref{sec:buildingCode})
+ then an executable called \texttt{mitgcmuv} will now exist in the
+ local directory.
+ To run the model as a single process (\textit{ie.} not in parallel)
+ simply type:
+ \begin{verbatim}
+ % ./mitgcmuv
+ \end{verbatim}
+ The ``./'' is a safe-guard to make sure you use the local executable
+ in case you have others that exist in your path (surely odd if you
+ do!). The above command will spew out many lines of text output to
+ your screen.  This output contains details such as parameter values as
+ well as diagnostics such as mean Kinetic energy, largest CFL number,
+ etc. It is worth keeping this text output with the binary output so we
+ normally re-direct the \texttt{stdout} stream as follows:
+ \begin{verbatim}
+ % ./mitgcmuv > output.txt
+ \end{verbatim}
+ In the event that the model encounters an error and stops, it is very
+ helpful to include the last few line of this \texttt{output.txt} file
+ along with the (\texttt{stderr}) error message within any bug reports.
+ For the example experiments in \texttt{verification}, an example of the
+ output is kept in \texttt{results/output.txt} for comparison. You can
+ compare your \texttt{output.txt} with the corresponding one for that
+ experiment to check that the set-up works.
+ \subsection{Output files}
+ The model produces various output files and, when using \texttt{mnc},
+ sometimes even directories.  Depending upon the I/O package(s)
+ selected at compile time (either \texttt{mdsio} or \texttt{mnc} or
+ both as determined by \texttt{code/packages.conf}) and the run-time
+ flags set (in \texttt{input/data.pkg}), the following output may
+ appear.
+ \subsubsection{MDSIO output files}
+ The ``traditional'' output files are generated by the \texttt{mdsio}
+ package.  At a minimum, the instantaneous ``state'' of the model is
+ written out, which is made of the following files:
+ \begin{itemize}
+ \item \texttt{U.00000nIter} - zonal component of velocity field (m/s
+   and positive eastward).
+ \item \texttt{V.00000nIter} - meridional component of velocity field
+   (m/s and positive northward).
+ \item \texttt{W.00000nIter} - vertical component of velocity field
+   (ocean: m/s and positive upward, atmosphere: Pa/s and positive
+   towards increasing pressure i.e. downward).
+ \item \texttt{T.00000nIter} - potential temperature (ocean:
+   $^{\circ}\mathrm{C}$, atmosphere: $^{\circ}\mathrm{K}$).
+ \item \texttt{S.00000nIter} - ocean: salinity (psu), atmosphere: water
+   vapor (g/kg).
+ \item \texttt{Eta.00000nIter} - ocean: surface elevation (m),
+   atmosphere: surface pressure anomaly (Pa).
+ \end{itemize}
+ The chain \texttt{00000nIter} consists of ten figures that specify the
+ iteration number at which the output is written out. For example,
+ \texttt{U.0000000300} is the zonal velocity at iteration 300.
  In addition, a ``pickup'' or ``checkpoint'' file called:
  \begin{itemize}
- \item \textit{pickup.00000nIter}
+ \item \texttt{pickup.00000nIter}
  \end{itemize}
  is written out. This file represents the state of the model in a condensed
-Line 440 
 form and is used for restarting the inte
+Line 898 
 form and is used for restarting the inte
  there is an additional ``pickup'' file:
  \begin{itemize}
- \item \textit{pickup\_cd.00000nIter}
+ \item \texttt{pickup\_cd.00000nIter}
  \end{itemize}
  containing the D-grid velocity data and that has to be written out as well
  in order to restart the integration. Rolling checkpoint files are the same
  as the pickup files but are named differently. Their name contain the chain
- \textit{ckptA} or \textit{ckptB} instead of \textit{00000nIter}. They can be
+ \texttt{ckptA} or \texttt{ckptB} instead of \texttt{00000nIter}. They can be
  used to restart the model but are overwritten every other time they are
  output to save disk space during long integrations.
- \subsubsection{Looking at the output}
+ \subsubsection{MNC output files}
- All the model data are written according to a ``meta/data'' file format.
- Each variable is associated with two files with suffix names \textit{.data}
- and \textit{.meta}. The \textit{.data} file contains the data written in
- binary form (big\_endian by default). The \textit{.meta} file is a
- ``header'' file that contains information about the size and the structure
- of the \textit{.data} file. This way of organizing the output is
- particularly useful when running multi-processors calculations. The base
- version of the model includes a few matlab utilities to read output files
- written in this format. The matlab scripts are located in the directory
- \textit{utils/matlab} under the root tree. The script \textit{rdmds.m} reads
- the data. Look at the comments inside the script to see how to use it.
- \section{Code structure}
- \section{Doing it yourself: customizing the code}
- \subsection{\protect\bigskip Configuration and setup}
- When you are ready to run the model in the configuration you want, the
- easiest thing is to use and adapt the setup of the case studies experiment
- (described previously) that is the closest to your configuration. Then, the
- amount of setup will be minimized. In this section, we focus on the setup
- relative to the ''numerical model'' part of the code (the setup relative to
- the ''execution environment'' part is covered in the parallel implementation
- section) and on the variables and parameters that you are likely to change.
- The CPP keys relative to the ''numerical model'' part of the code are all
- defined and set in the file \textit{CPP\_OPTIONS.h }in the directory \textit{%
- model/inc }or in one of the \textit{code }directories of the case study
- experiments under \textit{verification.} The model parameters are defined
- and declared in the file \textit{model/inc/PARAMS.h }and their default
- values are set in the routine \textit{model/src/set\_defaults.F. }The
- default values can be modified in the namelist file \textit{data }which
- needs to be located in the directory where you will run the model. The
- parameters are initialized in the routine \textit{model/src/ini\_parms.F}.
- Look at this routine to see in what part of the namelist the parameters are
- located.
- In what follows the parameters are grouped into categories related to the
- computational domain, the equations solved in the model, and the simulation
- controls.
- \subsubsection{Computational domain, geometry and time-discretization}
- \begin{itemize}
- \item dimensions
- \end{itemize}
- The number of points in the x, y,\textit{\ }and r\textit{\ }directions are
- represented by the variables \textbf{sNx}\textit{, }\textbf{sNy}\textit{, }%
- and \textbf{Nr}\textit{\ }respectively which are declared and set in the
- file \textit{model/inc/SIZE.h. }(Again, this assumes a mono-processor
- calculation. For multiprocessor calculations see section on parallel
- implementation.)
- \begin{itemize}
- \item grid
- \end{itemize}
- Three different grids are available: cartesian, spherical polar, and
- curvilinear (including the cubed sphere). The grid is set through the
- logical variables \textbf{usingCartesianGrid}\textit{, }\textbf{%
- usingSphericalPolarGrid}\textit{, }and \textit{\ }\textbf{%
- usingCurvilinearGrid}\textit{. }In the case of spherical and curvilinear
- grids, the southern boundary is defined through the variable \textbf{phiMin}%
- \textit{\ }which corresponds to the latitude of the southern most cell face
- (in degrees). The resolution along the x and y directions is controlled by
- the 1D arrays \textbf{delx}\textit{\ }and \textbf{dely}\textit{\ }(in meters
- in the case of a cartesian grid, in degrees otherwise). The vertical grid
- spacing is set through the 1D array \textbf{delz }for the ocean (in meters)
- or \textbf{delp}\textit{\ }for the atmosphere (in Pa). The variable \textbf{%
- Ro\_SeaLevel} represents the standard position of Sea-Level in ''R''
- coordinate. This is typically set to 0m for the ocean (default value) and 10$%
- ^{5}$Pa for the atmosphere. For the atmosphere, also set the logical
- variable \textbf{groundAtK1} to '.\texttt{TRUE}.'. which put the first level
- (k=1) at the lower boundary (ground).
- For the cartesian grid case, the Coriolis parameter $f$ is set through the
- variables \textbf{f0}\textit{\ }and \textbf{beta}\textit{\ }which correspond
- to the reference Coriolis parameter (in s$^{-1}$) and $\frac{\partial f}{%
- \partial y}$(in m$^{-1}$s$^{-1}$) respectively. If \textbf{beta }\textit{\ }%
- is set to a nonzero value, \textbf{f0}\textit{\ }is the value of $f$ at the
- southern edge of the domain.
- \begin{itemize}
- \item topography - full and partial cells
- \end{itemize}
- The domain bathymetry is read from a file that contains a 2D (x,y) map of
- depths (in m) for the ocean or pressures (in Pa) for the atmosphere. The
- file name is represented by the variable \textbf{bathyFile}\textit{. }The
- file is assumed to contain binary numbers giving the depth (pressure) of the
- model at each grid cell, ordered with the x coordinate varying fastest. The
- points are ordered from low coordinate to high coordinate for both axes. The
- model code applies without modification to enclosed, periodic, and double
- periodic domains. Periodicity is assumed by default and is suppressed by
- setting the depths to 0m for the cells at the limits of the computational
- domain (note: not sure this is the case for the atmosphere). The precision
- with which to read the binary data is controlled by the integer variable
- \textbf{readBinaryPrec }which can take the value \texttt{32} (single
- precision) or \texttt{64} (double precision). See the matlab program \textit{%
- gendata.m }in the \textit{input }directories under \textit{verification }to
- see how the bathymetry files are generated for the case study experiments.
- To use the partial cell capability, the variable \textbf{hFacMin}\textit{\ }%
- needs to be set to a value between 0 and 1 (it is set to 1 by default)
- corresponding to the minimum fractional size of the cell. For example if the
- bottom cell is 500m thick and \textbf{hFacMin}\textit{\ }is set to 0.1, the
- actual thickness of the cell (i.e. used in the code) can cover a range of
- discrete values 50m apart from 50m to 500m depending on the value of the
- bottom depth (in \textbf{bathyFile}) at this point.
- Note that the bottom depths (or pressures) need not coincide with the models
- levels as deduced from \textbf{delz}\textit{\ }or\textit{\ }\textbf{delp}%
- \textit{. }The model will interpolate the numbers in \textbf{bathyFile}%
- \textit{\ }so that they match the levels obtained from \textbf{delz}\textit{%
- \ }or\textit{\ }\textbf{delp}\textit{\ }and \textbf{hFacMin}\textit{. }
- (Note: the atmospheric case is a bit more complicated than what is written
- here I think. To come soon...)
- \begin{itemize}
+ Unlike the \texttt{mdsio} output, the \texttt{mnc}--generated output
- \item time-discretization
+ is usually (though not necessarily) placed within a subdirectory with
- \end{itemize}
+ a name such as \texttt{mnc\_test\_\${DATE}\_\${SEQ}}.
- The time steps are set through the real variables \textbf{deltaTMom }and
- \textbf{deltaTtracer }(in s) which represent the time step for the momentum
- and tracer equations, respectively. For synchronous integrations, simply set
- the two variables to the same value (or you can prescribe one time step only
- through the variable \textbf{deltaT}). The Adams-Bashforth stabilizing
- parameter is set through the variable \textbf{abEps }(dimensionless). The
- stagger baroclinic time stepping can be activated by setting the logical
- variable \textbf{staggerTimeStep }to '.\texttt{TRUE}.'.
- \subsubsection{Equation of state}
- First, because the model equations are written in terms of perturbations, a
- reference thermodynamic state needs to be specified. This is done through
- the 1D arrays \textbf{tRef}\textit{\ }and \textbf{sRef}. \textbf{tRef }%
- specifies the reference potential temperature profile (in $^{o}$C for
- the ocean and $^{o}$K for the atmosphere) starting from the level
- k=1. Similarly, \textbf{sRef}\textit{\ }specifies the reference salinity
- profile (in ppt) for the ocean or the reference specific humidity profile
- (in g/kg) for the atmosphere.
- The form of the equation of state is controlled by the character variables
- \textbf{buoyancyRelation}\textit{\ }and \textbf{eosType}\textit{. }\textbf{%
- buoyancyRelation}\textit{\ }is set to '\texttt{OCEANIC}' by default and
- needs to be set to '\texttt{ATMOSPHERIC}' for atmosphere simulations. In
- this case, \textbf{eosType}\textit{\ }must be set to '\texttt{IDEALGAS}'.
- For the ocean, two forms of the equation of state are available: linear (set
- \textbf{eosType}\textit{\ }to '\texttt{LINEAR}') and a polynomial
- approximation to the full nonlinear equation ( set \textbf{eosType}\textit{\
- }to '\texttt{POLYNOMIAL}'). In the linear case, you need to specify the
- thermal and haline expansion coefficients represented by the variables
- \textbf{tAlpha}\textit{\ }(in K$^{-1}$) and \textbf{sBeta}\textit{\ }(in ppt$%
- ^{-1}$). For the nonlinear case, you need to generate a file of polynomial
- coefficients called \textit{POLY3.COEFFS. }To do this, use the program
- \textit{utils/knudsen2/knudsen2.f }under the model tree (a Makefile is
- available in the same directory and you will need to edit the number and the
- values of the vertical levels in \textit{knudsen2.f }so that they match
- those of your configuration). \textit{\ }
- \subsubsection{Momentum equations}
- In this section, we only focus for now on the parameters that you are likely
- to change, i.e. the ones relative to forcing and dissipation for example.
- The details relevant to the vector-invariant form of the equations and the
- various advection schemes are not covered for the moment. We assume that you
- use the standard form of the momentum equations (i.e. the flux-form) with
- the default advection scheme. Also, there are a few logical variables that
- allow you to turn on/off various terms in the momentum equation. These
- variables are called \textbf{momViscosity, momAdvection, momForcing,
- useCoriolis, momPressureForcing, momStepping}\textit{, }and \textit{\ }%
- \textbf{metricTerms }and are assumed to be set to '.\texttt{TRUE}.' here.
- Look at the file \textit{model/inc/PARAMS.h }for a precise definition of
- these variables.
- \begin{itemize}
- \item initialization
- \end{itemize}
- The velocity components are initialized to 0 unless the simulation is
- starting from a pickup file (see section on simulation control parameters).
- \begin{itemize}
- \item forcing
- \end{itemize}
- This section only applies to the ocean. You need to generate wind-stress
- data into two files \textbf{zonalWindFile}\textit{\ }and \textbf{%
- meridWindFile }corresponding to the zonal and meridional components of the
- wind stress, respectively (if you want the stress to be along the direction
- of only one of the model horizontal axes, you only need to generate one
- file). The format of the files is similar to the bathymetry file. The zonal
- (meridional) stress data are assumed to be in Pa and located at U-points
- (V-points). As for the bathymetry, the precision with which to read the
- binary data is controlled by the variable \textbf{readBinaryPrec}.\textbf{\ }
- See the matlab program \textit{gendata.m }in the \textit{input }directories
- under \textit{verification }to see how simple analytical wind forcing data
- are generated for the case study experiments.
- There is also the possibility of prescribing time-dependent periodic
- forcing. To do this, concatenate the successive time records into a single
- file (for each stress component) ordered in a (x, y, t) fashion and set the
- following variables: \textbf{periodicExternalForcing }to '.\texttt{TRUE}.',
- \textbf{externForcingPeriod }to the period (in s) of which the forcing
- varies (typically 1 month), and \textbf{externForcingCycle }to the repeat
- time (in s) of the forcing (typically 1 year -- note: \textbf{%
- externForcingCycle }must be a multiple of \textbf{externForcingPeriod}).
- With these variables set up, the model will interpolate the forcing linearly
- at each iteration.
- \begin{itemize}
+ \subsection{Looking at the output}
- \item dissipation
- \end{itemize}
- The lateral eddy viscosity coefficient is specified through the variable
- \textbf{viscAh}\textit{\ }(in m$^{2}$s$^{-1}$). The vertical eddy viscosity
- coefficient is specified through the variable \textbf{viscAz }(in m$^{2}$s$%
- ^{-1}$) for the ocean and \textbf{viscAp}\textit{\ }(in Pa$^{2}$s$^{-1}$)
- for the atmosphere. The vertical diffusive fluxes can be computed implicitly
- by setting the logical variable \textbf{implicitViscosity }to '.\texttt{TRUE}%
- .'. In addition, biharmonic mixing can be added as well through the variable
- \textbf{viscA4}\textit{\ }(in m$^{4}$s$^{-1}$). On a spherical polar grid,
- you might also need to set the variable \textbf{cosPower} which is set to 0
- by default and which represents the power of cosine of latitude to multiply
- viscosity. Slip or no-slip conditions at lateral and bottom boundaries are
- specified through the logical variables \textbf{no\_slip\_sides}\textit{\ }%
- and \textbf{no\_slip\_bottom}. If set to '\texttt{.FALSE.}', free-slip
- boundary conditions are applied. If no-slip boundary conditions are applied
- at the bottom, a bottom drag can be applied as well. Two forms are
- available: linear (set the variable \textbf{bottomDragLinear}\textit{\ }in s$%
- ^{-1}$) and quadratic (set the variable \textbf{bottomDragQuadratic}\textit{%
- \ }in m$^{-1}$).
- The Fourier and Shapiro filters are described elsewhere.
- \begin{itemize}
- \item C-D scheme
- \end{itemize}
- If you run at a sufficiently coarse resolution, you will need the C-D scheme
- for the computation of the Coriolis terms. The variable\textbf{\ tauCD},
- which represents the C-D scheme coupling timescale (in s) needs to be set.
- \begin{itemize}
- \item calculation of pressure/geopotential
- \end{itemize}
- First, to run a non-hydrostatic ocean simulation, set the logical variable
- \textbf{nonHydrostatic} to '.\texttt{TRUE}.'. The pressure field is then
- inverted through a 3D elliptic equation. (Note: this capability is not
- available for the atmosphere yet.) By default, a hydrostatic simulation is
- assumed and a 2D elliptic equation is used to invert the pressure field. The
- parameters controlling the behaviour of the elliptic solvers are the
- variables \textbf{cg2dMaxIters}\textit{\ }and \textbf{cg2dTargetResidual }%
- for the 2D case and \textbf{cg3dMaxIters}\textit{\ }and \textbf{%
- cg3dTargetResidual }for the 3D case. You probably won't need to alter the
- default values (are we sure of this?).
- For the calculation of the surface pressure (for the ocean) or surface
- geopotential (for the atmosphere) you need to set the logical variables
- \textbf{rigidLid} and \textbf{implicitFreeSurface}\textit{\ }(set one to '.%
- \texttt{TRUE}.' and the other to '.\texttt{FALSE}.' depending on how you
- want to deal with the ocean upper or atmosphere lower boundary).
- \subsubsection{Tracer equations}
- This section covers the tracer equations i.e. the potential temperature
- equation and the salinity (for the ocean) or specific humidity (for the
- atmosphere) equation. As for the momentum equations, we only describe for
- now the parameters that you are likely to change. The logical variables
- \textbf{tempDiffusion}\textit{, }\textbf{tempAdvection}\textit{, }\textbf{%
- tempForcing}\textit{,} and \textbf{tempStepping} allow you to turn on/off
- terms in the temperature equation (same thing for salinity or specific
- humidity with variables \textbf{saltDiffusion}\textit{, }\textbf{%
- saltAdvection}\textit{\ }etc). These variables are all assumed here to be
- set to '.\texttt{TRUE}.'. Look at file \textit{model/inc/PARAMS.h }for a
- precise definition.
- \begin{itemize}
- \item initialization
- \end{itemize}
- The initial tracer data can be contained in the binary files \textbf{%
+ The ``traditional'' or mdsio model data are written according to a
- hydrogThetaFile }and \textbf{hydrogSaltFile}. These files should contain 3D
+ ``meta/data'' file format.  Each variable is associated with two files
- data ordered in an (x, y, r) fashion with k=1 as the first vertical level.
+ with suffix names \texttt{.data} and \texttt{.meta}. The
- If no file names are provided, the tracers are then initialized with the
+ \texttt{.data} file contains the data written in binary form
- values of \textbf{tRef }and \textbf{sRef }mentioned above (in the equation
+ (big\_endian by default). The \texttt{.meta} file is a ``header'' file
- of state section). In this case, the initial tracer data are uniform in x
+ that contains information about the size and the structure of the
- and y for each depth level.
+ \texttt{.data} file. This way of organizing the output is particularly
+ useful when running multi-processors calculations. The base version of
+ the model includes a few matlab utilities to read output files written
+ in this format. The matlab scripts are located in the directory
+ \texttt{utils/matlab} under the root tree. The script \texttt{rdmds.m}
+ reads the data. Look at the comments inside the script to see how to
+ use it.
- \begin{itemize}
+ Some examples of reading and visualizing some output in {\em Matlab}:
- \item forcing
+ \begin{verbatim}
- \end{itemize}
+ % matlab
+ >> H=rdmds('Depth');
- This part is more relevant for the ocean, the procedure for the atmosphere
+ >> contourf(H');colorbar;
- not being completely stabilized at the moment.
+ >> title('Depth of fluid as used by model');
- A combination of fluxes data and relaxation terms can be used for driving
- the tracer equations. \ For potential temperature, heat flux data (in W/m$%
- ^{2}$) can be stored in the 2D binary file \textbf{surfQfile}\textit{. }%
- Alternatively or in addition, the forcing can be specified through a
- relaxation term. The SST data to which the model surface temperatures are
- restored to are supposed to be stored in the 2D binary file \textbf{%
- thetaClimFile}\textit{. }The corresponding relaxation time scale coefficient
- is set through the variable \textbf{tauThetaClimRelax}\textit{\ }(in s). The
- same procedure applies for salinity with the variable names \textbf{EmPmRfile%
- }\textit{, }\textbf{saltClimFile}\textit{, }and \textbf{tauSaltClimRelax}%
- \textit{\ }for freshwater flux (in m/s) and surface salinity (in ppt) data
- files and relaxation time scale coefficient (in s), respectively. Also for
- salinity, if the CPP key \textbf{USE\_NATURAL\_BCS} is turned on, natural
- boundary conditions are applied i.e. when computing the surface salinity
- tendency, the freshwater flux is multiplied by the model surface salinity
- instead of a constant salinity value.
- As for the other input files, the precision with which to read the data is
- controlled by the variable \textbf{readBinaryPrec}. Time-dependent, periodic
- forcing can be applied as well following the same procedure used for the
- wind forcing data (see above).
- \begin{itemize}
- \item dissipation
- \end{itemize}
- Lateral eddy diffusivities for temperature and salinity/specific humidity
+ >> eta=rdmds('Eta',10);
- are specified through the variables \textbf{diffKhT }and \textbf{diffKhS }%
+ >> imagesc(eta');axis ij;colorbar;
- (in m$^{2}$/s). Vertical eddy diffusivities are specified through the
+ >> title('Surface height at iter=10');
- variables \textbf{diffKzT }and \textbf{diffKzS }(in m$^{2}$/s) for the ocean
- and \textbf{diffKpT }and \textbf{diffKpS }(in Pa$^{2}$/s) for the
- atmosphere. The vertical diffusive fluxes can be computed implicitly by
- setting the logical variable \textbf{implicitDiffusion }to '.\texttt{TRUE}%
- .'. In addition, biharmonic diffusivities can be specified as well through
- the coefficients \textbf{diffK4T }and \textbf{diffK4S }(in m$^{4}$/s). Note
- that the cosine power scaling (specified through \textbf{cosPower }- see the
- momentum equations section) is applied to the tracer diffusivities
- (Laplacian and biharmonic) as well. The Gent and McWilliams parameterization
- for oceanic tracers is described in the package section. Finally, note that
- tracers can be also subject to Fourier and Shapiro filtering (see the
- corresponding section on these filters).
- \begin{itemize}
+ >> eta=rdmds('Eta',[0:10:100]);
- \item ocean convection
+ >> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end
- \end{itemize}
+ \end{verbatim}
- Two options are available to parameterize ocean convection: one is to use
+ Similar scripts for netCDF output (\texttt{rdmnc.m}) are available and
- the convective adjustment scheme. In this case, you need to set the variable
+ they are described in Section \ref{sec:pkg:mnc}.
- \textbf{cadjFreq}, which represents the frequency (in s) with which the
- adjustment algorithm is called, to a non-zero value (if set to a negative
- value by the user, the model will set it to the tracer time step). The other
- option is to parameterize convection with implicit vertical diffusion. To do
- this, set the logical variable \textbf{implicitDiffusion }to '.\texttt{TRUE}%
- .' and the real variable \textbf{ivdc\_kappa }to a value (in m$^{2}$/s) you
- wish the tracer vertical diffusivities to have when mixing tracers
- vertically due to static instabilities. Note that \textbf{cadjFreq }and
- \textbf{ivdc\_kappa }can not both have non-zero value.
- \subsubsection{Simulation controls}
- The model ''clock'' is defined by the variable \textbf{deltaTClock }(in s)
- which determines the IO frequencies and is used in tagging output.
- Typically, you will set it to the tracer time step for accelerated runs
- (otherwise it is simply set to the default time step \textbf{deltaT}).
- Frequency of checkpointing and dumping of the model state are referenced to
- this clock (see below).
+ The MNC output files are all in the ``self-describing'' netCDF
+ format and can thus be browsed and/or plotted using tools such as:
  \begin{itemize}
- \item run duration
+ \item \texttt{ncdump} is a utility which is typically included
- \end{itemize}
+   with every netCDF install:
+   \begin{rawhtml} <A href="http://www.unidata.ucar.edu/packages/netcdf/"> \end{rawhtml}
- The beginning of a simulation is set by specifying a start time (in s)
+ \begin{verbatim}
- through the real variable \textbf{startTime }or by specifying an initial
+ http://www.unidata.ucar.edu/packages/netcdf/
- iteration number through the integer variable \textbf{nIter0}. If these
+ \end{verbatim}
- variables are set to nonzero values, the model will look for a ''pickup''
+   \begin{rawhtml} </A> \end{rawhtml} and it converts the netCDF
- file \textit{pickup.0000nIter0 }to restart the integration\textit{. }The end
+   binaries into formatted ASCII text files.
- of a simulation is set through the real variable \textbf{endTime }(in s).
- Alternatively, you can specify instead the number of time steps to execute
- through the integer variable \textbf{nTimeSteps}.
- \begin{itemize}
+ \item \texttt{ncview} utility is a very convenient and quick way
- \item frequency of output
+   to plot netCDF data and it runs on most OSes:
+   \begin{rawhtml} <A href="http://meteora.ucsd.edu/~pierce/ncview_home_page.html"> \end{rawhtml}
+ \begin{verbatim}
+ http://meteora.ucsd.edu/~pierce/ncview_home_page.html
+ \end{verbatim}
+   \begin{rawhtml} </A> \end{rawhtml}
+ \item MatLAB(c) and other common post-processing environments provide
+   various netCDF interfaces including:
+   \begin{rawhtml} <A href="http://mexcdf.sourceforge.net/"> \end{rawhtml}
+ \begin{verbatim}
+ http://mexcdf.sourceforge.net/
+ \end{verbatim}
+   \begin{rawhtml} </A> \end{rawhtml}
+   \begin{rawhtml} <A href="http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html"> \end{rawhtml}
+ \begin{verbatim}
+ http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html
+ \end{verbatim}
+   \begin{rawhtml} </A> \end{rawhtml}
  \end{itemize}
- Real variables defining frequencies (in s) with which output files are
- written on disk need to be set up. \textbf{dumpFreq }controls the frequency
- with which the instantaneous state of the model is saved. \textbf{chkPtFreq }%
- and \textbf{pchkPtFreq }control the output frequency of rolling and
- permanent checkpoint files, respectively. See section 1.5.1 Output files for the
- definition of model state and checkpoint files. In addition, time-averaged
- fields can be written out by setting the variable \textbf{taveFreq} (in s).
- The precision with which to write the binary data is controlled by the
- integer variable w\textbf{riteBinaryPrec }(set it to \texttt{32} or \texttt{%
-}).

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