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3    
4  %\section{Getting started}  %\section{Getting started}
5    
6  In this section, we describe how to use the model. In the first  We believe the best way to familiarize yourself with the
 section, we provide enough information to help you get started with  
 the model. We believe the best way to familiarize yourself with the  
7  model is to run the case study examples provided with the base  model is to run the case study examples provided with the base
8  version. Information on how to obtain, compile, and run the code is  version. Information on how to obtain, compile, and run the code is
9  found there as well as a brief description of the model structure  found here as well as a brief description of the model structure
10  directory and the case study examples.  The latter and the code  directory and the case study examples. Information is also provided
11  structure are described more fully in chapters  here on how to customize the code when you are ready to try implementing
12  \ref{chap:discretization} and \ref{chap:sarch}, respectively. Here, in  the configuration you have in mind.  The code and algorithm
13  this section, we provide information on how to customize the code when  are described more fully in chapters \ref{chap:discretization} and
14  you are ready to try implementing the configuration you have in mind.  \ref{chap:sarch}.
15    
16  \section{Where to find information}  \section{Where to find information}
17  \label{sect:whereToFindInfo}  \label{sect:whereToFindInfo}
18    \begin{rawhtml}
19  A web site is maintained for release 1 (Sealion) of MITgcm:  <!-- CMIREDIR:whereToFindInfo: -->
20    \end{rawhtml}
21    
22    There is a web-archived support mailing list for the model that
23    you can email at \texttt{MITgcm-support@mitgcm.org} or browse at:
24    \begin{rawhtml} <A href=http://mitgcm.org/mailman/listinfo/mitgcm-support/ target="idontexist"> \end{rawhtml}
25  \begin{verbatim}  \begin{verbatim}
26  http://mitgcm.org/sealion  http://mitgcm.org/mailman/listinfo/mitgcm-support/
27    http://mitgcm.org/pipermail/mitgcm-support/
28  \end{verbatim}  \end{verbatim}
29  Here you will find an on-line version of this document, a  \begin{rawhtml} </A> \end{rawhtml}
 ``browsable'' copy of the code and a searchable database of the model  
 and site, as well as links for downloading the model and  
 documentation, to data-sources and other related sites.  
   
 There is also a support news group for the model that you can email at  
 \texttt{support@mitgcm.org} or browse at:  
 \begin{verbatim}  
 news://mitgcm.org/mitgcm.support  
 \end{verbatim}  
 A mail to the email list will reach all the developers and be archived  
 on the newsgroup. A users email list will be established at some time  
 in the future.  
   
30    
31  \section{Obtaining the code}  \section{Obtaining the code}
32  \label{sect:obtainingCode}  \label{sect:obtainingCode}
33    \begin{rawhtml}
34    <!-- CMIREDIR:obtainingCode: -->
35    \end{rawhtml}
36    
37    MITgcm can be downloaded from our system by following
38    the instructions below. As a courtesy we ask that you send e-mail to us at
39    \begin{rawhtml} <A href=mailto:MITgcm-support@mitgcm.org> \end{rawhtml}
40    MITgcm-support@mitgcm.org
41    \begin{rawhtml} </A> \end{rawhtml}
42    to enable us to keep track of who's using the model and in what application.
43    You can download the model two ways:
44    
45    \begin{enumerate}
46    \item Using CVS software. CVS is a freely available source code management
47    tool. To use CVS you need to have the software installed. Many systems
48    come with CVS pre-installed, otherwise good places to look for
49    the software for a particular platform are
50    \begin{rawhtml} <A href=http://www.cvshome.org/ target="idontexist"> \end{rawhtml}
51    cvshome.org
52    \begin{rawhtml} </A> \end{rawhtml}
53    and
54    \begin{rawhtml} <A href=http://www.wincvs.org/ target="idontexist"> \end{rawhtml}
55    wincvs.org
56    \begin{rawhtml} </A> \end{rawhtml}
57    .
58    
59    \item Using a tar file. This method is simple and does not
60    require any special software. However, this method does not
61    provide easy support for maintenance updates.
62    
63    \end{enumerate}
64    
65    \subsection{Method 1 - Checkout from CVS}
66    \label{sect:cvs_checkout}
67    
68  If CVS is available on your system, we strongly encourage you to use it. CVS  If CVS is available on your system, we strongly encourage you to use it. CVS
69  provides an efficient and elegant way of organizing your code and keeping  provides an efficient and elegant way of organizing your code and keeping
70  track of your changes. If CVS is not available on your machine, you can also  track of your changes. If CVS is not available on your machine, you can also
71  download a tar file.  download a tar file.
72    
73  Before you can use CVS, the following environment variable has to be set in  Before you can use CVS, the following environment variable(s) should
74  your .cshrc or .tcshrc:  be set within your shell.  For a csh or tcsh shell, put the following
75  \begin{verbatim}  \begin{verbatim}
76  % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/u0/gcmpack  % setenv CVSROOT :pserver:cvsanon@mitgcm.org:/u/gcmpack
77  \end{verbatim}  \end{verbatim}
78    in your \texttt{.cshrc} or \texttt{.tcshrc} file.  For bash or sh
79  To start using CVS, "login" to the server using:  shells, put:
80  \begin{verbatim}  \begin{verbatim}
81  % cvs login ( CVS password: cvsanon )  % export CVSROOT=':pserver:cvsanon@mitgcm.org:/u/gcmpack'
82  \end{verbatim}  \end{verbatim}
83  You only need to do ``cvs login'' once.  in your \texttt{.profile} or \texttt{.bashrc} file.
84    
85    
86  To obtain the source for the release:  To get MITgcm through CVS, first register with the MITgcm CVS server
87    using command:
88  \begin{verbatim}  \begin{verbatim}
89  % cvs co -d directory -P -r release1 MITgcmUV  % cvs login ( CVS password: cvsanon )
90  \end{verbatim}  \end{verbatim}
91    You only need to do a ``cvs login'' once.
92    
93  This creates a directory called \textit{directory}. If \textit{directory}  To obtain the latest sources type:
 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  
 different \textit{version} that is not the latest source:  
94  \begin{verbatim}  \begin{verbatim}
95  % cvs co -d directory -P -r version MITgcm  % cvs co MITgcm
96  \end{verbatim}  \end{verbatim}
97  or the latest development version:  or to get a specific release type:
98  \begin{verbatim}  \begin{verbatim}
99  % cvs co -d directory -P MITgcm  % cvs co -P -r checkpoint52i_post  MITgcm
100  \end{verbatim}  \end{verbatim}
101    The MITgcm web site contains further directions concerning the source
102    code and CVS.  It also contains a web interface to our CVS archive so
103    that one may easily view the state of files, revisions, and other
104    development milestones:
105    \begin{rawhtml} <A href="http://mitgcm.org/download" target="idontexist"> \end{rawhtml}
106    \begin{verbatim}
107    http://mitgcm.org/source_code.html
108    \end{verbatim}
109    \begin{rawhtml} </A> \end{rawhtml}
110    
111    As a convenience, the MITgcm CVS server contains aliases which are
112    named subsets of the codebase.  These aliases can be especially
113    helpful when used over slow internet connections or on machines with
114    restricted storage space.  Table \ref{tab:cvsModules} contains a list
115    of CVS aliases
116    \begin{table}[htb]
117      \centering
118      \begin{tabular}[htb]{|lp{3.25in}|}\hline
119        \textbf{Alias Name}    &  \textbf{Information (directories) Contained}  \\\hline
120        \texttt{MITgcm\_code}  &  Only the source code -- none of the verification examples.  \\
121        \texttt{MITgcm\_verif\_basic}
122        &  Source code plus a small set of the verification examples
123        (\texttt{global\_ocean.90x40x15}, \texttt{aim.5l\_cs}, \texttt{hs94.128x64x5},
124        \texttt{front\_relax}, and \texttt{plume\_on\_slope}).  \\
125        \texttt{MITgcm\_verif\_atmos}  &  Source code plus all of the atmospheric examples.  \\
126        \texttt{MITgcm\_verif\_ocean}  &  Source code plus all of the oceanic examples.  \\
127        \texttt{MITgcm\_verif\_all}    &  Source code plus all of the
128        verification examples. \\\hline
129      \end{tabular}
130      \caption{MITgcm CVS Modules}
131      \label{tab:cvsModules}
132    \end{table}
133    
134    The checkout process creates a directory called \texttt{MITgcm}. If
135    the directory \texttt{MITgcm} exists this command updates your code
136    based on the repository. Each directory in the source tree contains a
137    directory \texttt{CVS}. This information is required by CVS to keep
138    track of your file versions with respect to the repository. Don't edit
139    the files in \texttt{CVS}!  You can also use CVS to download code
140    updates.  More extensive information on using CVS for maintaining
141    MITgcm code can be found
142    \begin{rawhtml} <A href="http://mitgcm.org/usingcvstoget.html" target="idontexist"> \end{rawhtml}
143    here
144    \begin{rawhtml} </A> \end{rawhtml}
145    .
146    It is important to note that the CVS aliases in Table
147    \ref{tab:cvsModules} cannot be used in conjunction with the CVS
148    \texttt{-d DIRNAME} option.  However, the \texttt{MITgcm} directories
149    they create can be changed to a different name following the check-out:
150    \begin{verbatim}
151       %  cvs co MITgcm_verif_basic
152       %  mv MITgcm MITgcm_verif_basic
153    \end{verbatim}
154    
155    \subsubsection{Upgrading from an earlier version}
156    
157    If you already have an earlier version of the code you can ``upgrade''
158    your copy instead of downloading the entire repository again. First,
159    ``cd'' (change directory) to the top of your working copy:
160    \begin{verbatim}
161    % cd MITgcm
162    \end{verbatim}
163    and then issue the cvs update command such as:
164    \begin{verbatim}
165    % cvs -q update -r checkpoint52i_post -d -P
166    \end{verbatim}
167    This will update the ``tag'' to ``checkpoint52i\_post'', add any new
168    directories (-d) and remove any empty directories (-P). The -q option
169    means be quiet which will reduce the number of messages you'll see in
170    the terminal. If you have modified the code prior to upgrading, CVS
171    will try to merge your changes with the upgrades. If there is a
172    conflict between your modifications and the upgrade, it will report
173    that file with a ``C'' in front, e.g.:
174    \begin{verbatim}
175    C model/src/ini_parms.F
176    \end{verbatim}
177    If the list of conflicts scrolled off the screen, you can re-issue the
178    cvs update command and it will report the conflicts. Conflicts are
179    indicated in the code by the delimites ``$<<<<<<<$'', ``======='' and
180    ``$>>>>>>>$''. For example,
181    {\small
182    \begin{verbatim}
183    <<<<<<< ini_parms.F
184         & bottomDragLinear,myOwnBottomDragCoefficient,
185    =======
186         & bottomDragLinear,bottomDragQuadratic,
187    >>>>>>> 1.18
188    \end{verbatim}
189    }
190    means that you added ``myOwnBottomDragCoefficient'' to a namelist at
191    the same time and place that we added ``bottomDragQuadratic''. You
192    need to resolve this conflict and in this case the line should be
193    changed to:
194    {\small
195    \begin{verbatim}
196         & bottomDragLinear,bottomDragQuadratic,myOwnBottomDragCoefficient,
197    \end{verbatim}
198    }
199    and the lines with the delimiters ($<<<<<<$,======,$>>>>>>$) be deleted.
200    Unless you are making modifications which exactly parallel
201    developments we make, these types of conflicts should be rare.
202    
203    \paragraph*{Upgrading to the current pre-release version}
204    
205    We don't make a ``release'' for every little patch and bug fix in
206    order to keep the frequency of upgrades to a minimum. However, if you
207    have run into a problem for which ``we have already fixed in the
208    latest code'' and we haven't made a ``tag'' or ``release'' since that
209    patch then you'll need to get the latest code:
210    \begin{verbatim}
211    % cvs -q update -A -d -P
212    \end{verbatim}
213    Unlike, the ``check-out'' and ``update'' procedures above, there is no
214    ``tag'' or release name. The -A tells CVS to upgrade to the
215    very latest version. As a rule, we don't recommend this since you
216    might upgrade while we are in the processes of checking in the code so
217    that you may only have part of a patch. Using this method of updating
218    also means we can't tell what version of the code you are working
219    with. So please be sure you understand what you're doing.
220    
221  \paragraph*{Conventional download method}  \subsection{Method 2 - Tar file download}
222  \label{sect:conventionalDownload}  \label{sect:conventionalDownload}
223    
224  If you do not have CVS on your system, you can download the model as a  If you do not have CVS on your system, you can download the model as a
225  tar file from the reference web site at:  tar file from the web site at:
226    \begin{rawhtml} <A href=http://mitgcm.org/download target="idontexist"> \end{rawhtml}
227  \begin{verbatim}  \begin{verbatim}
228  http://mitgcm.org/download/  http://mitgcm.org/download/
229  \end{verbatim}  \end{verbatim}
230    \begin{rawhtml} </A> \end{rawhtml}
231  The tar file still contains CVS information which we urge you not to  The tar file still contains CVS information which we urge you not to
232  delete; even if you do not use CVS yourself the information can help  delete; even if you do not use CVS yourself the information can help
233  us if you should need to send us your copy of the code.  us if you should need to send us your copy of the code.  If a recent
234    tar file does not exist, then please contact the developers through
235    the
236    \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
237    MITgcm-support@mitgcm.org
238    \begin{rawhtml} </A> \end{rawhtml}
239    mailing list.
240    
241  \section{Model and directory structure}  \section{Model and directory structure}
242    \begin{rawhtml}
243  The ``numerical'' model is contained within a execution environment support  <!-- CMIREDIR:directory_structure: -->
244  wrapper. This wrapper is designed to provide a general framework for  \end{rawhtml}
245  grid-point models. MITgcmUV is a specific numerical model that uses the  
246  framework. Under this structure the model is split into execution  The ``numerical'' model is contained within a execution environment
247  environment support code and conventional numerical model code. The  support wrapper. This wrapper is designed to provide a general
248  execution environment support code is held under the \textit{eesupp}  framework for grid-point models. MITgcmUV is a specific numerical
249  directory. The grid point model code is held under the \textit{model}  model that uses the framework. Under this structure the model is split
250  directory. Code execution actually starts in the \textit{eesupp} routines  into execution environment support code and conventional numerical
251  and not in the \textit{model} routines. For this reason the top-level  model code. The execution environment support code is held under the
252  \textit{MAIN.F} is in the \textit{eesupp/src} directory. In general,  \texttt{eesupp} directory. The grid point model code is held under the
253  end-users should not need to worry about this level. The top-level routine  \texttt{model} directory. Code execution actually starts in the
254  for the numerical part of the code is in \textit{model/src/THE\_MODEL\_MAIN.F%  \texttt{eesupp} routines and not in the \texttt{model} routines. For
255  }. Here is a brief description of the directory structure of the model under  this reason the top-level \texttt{MAIN.F} is in the
256  the root tree (a detailed description is given in section 3: Code structure).  \texttt{eesupp/src} directory. In general, end-users should not need
257    to worry about this level. The top-level routine for the numerical
258  \begin{itemize}  part of the code is in \texttt{model/src/THE\_MODEL\_MAIN.F}. Here is
259  \item \textit{bin}: this directory is initially empty. It is the default  a brief description of the directory structure of the model under the
260  directory in which to compile the code.  root tree (a detailed description is given in section 3: Code
261    structure).
262  \item \textit{diags}: contains the code relative to time-averaged  
263  diagnostics. It is subdivided into two subdirectories \textit{inc} and  \begin{itemize}
264  \textit{src} that contain include files (*.\textit{h} files) and fortran  
265  subroutines (*.\textit{F} files), respectively.  \item \texttt{doc}: contains brief documentation notes.
266      
267  \item \textit{doc}: contains brief documentation notes.  \item \texttt{eesupp}: contains the execution environment source code.
268      Also subdivided into two subdirectories \texttt{inc} and
269  \item \textit{eesupp}: contains the execution environment source code. Also    \texttt{src}.
270  subdivided into two subdirectories \textit{inc} and \textit{src}.    
271    \item \texttt{model}: this directory contains the main source code.
272  \item \textit{exe}: this directory is initially empty. It is the default    Also subdivided into two subdirectories \texttt{inc} and
273  directory in which to execute the code.    \texttt{src}.
274      
275  \item \textit{model}: this directory contains the main source code. Also  \item \texttt{pkg}: contains the source code for the packages. Each
276  subdivided into two subdirectories \textit{inc} and \textit{src}.    package corresponds to a subdirectory. For example, \texttt{gmredi}
277      contains the code related to the Gent-McWilliams/Redi scheme,
278  \item \textit{pkg}: contains the source code for the packages. Each package    \texttt{aim} the code relative to the atmospheric intermediate
279  corresponds to a subdirectory. For example, \textit{gmredi} contains the    physics. The packages are described in detail in chapter \ref{chap.packagesI}.
280  code related to the Gent-McWilliams/Redi scheme, \textit{aim} the code    
281  relative to the atmospheric intermediate physics. The packages are described  \item \texttt{tools}: this directory contains various useful tools.
282  in detail in section 3.    For example, \texttt{genmake2} is a script written in csh (C-shell)
283      that should be used to generate your makefile. The directory
284  \item \textit{tools}: this directory contains various useful tools. For    \texttt{adjoint} contains the makefile specific to the Tangent
285  example, \textit{genmake} is a script written in csh (C-shell) that should    linear and Adjoint Compiler (TAMC) that generates the adjoint code.
286  be used to generate your makefile. The directory \textit{adjoint} contains    The latter is described in detail in part \ref{chap.ecco}.
287  the makefile specific to the Tangent linear and Adjoint Compiler (TAMC) that    This directory also contains the subdirectory build\_options, which
288  generates the adjoint code. The latter is described in details in part V.    contains the `optfiles' with the compiler options for the different
289      compilers and machines that can run MITgcm.
290  \item \textit{utils}: this directory contains various utilities. The    
291  subdirectory \textit{knudsen2} contains code and a makefile that  \item \texttt{utils}: this directory contains various utilities. The
292  compute coefficients of the polynomial approximation to the knudsen    subdirectory \texttt{knudsen2} contains code and a makefile that
293  formula for an ocean nonlinear equation of state. The \textit{matlab}    compute coefficients of the polynomial approximation to the knudsen
294  subdirectory contains matlab scripts for reading model output directly    formula for an ocean nonlinear equation of state. The
295  into matlab. \textit{scripts} contains C-shell post-processing    \texttt{matlab} subdirectory contains matlab scripts for reading
296  scripts for joining processor-based and tiled-based model output.    model output directly into matlab. \texttt{scripts} contains C-shell
297      post-processing scripts for joining processor-based and tiled-based
298  \item \textit{verification}: this directory contains the model examples. See    model output. The subdirectory exch2 contains the code needed for
299  section \ref{sect:modelExamples}.    the exch2 package to work with different combinations of domain
300  \end{itemize}    decompositions.
301      
302  \section{Example experiments}  \item \texttt{verification}: this directory contains the model
303  \label{sect:modelExamples}    examples. See section \ref{sect:modelExamples}.
304    
305  Now that you have successfully downloaded the model code we recommend that  \item \texttt{jobs}: contains sample job scripts for running MITgcm.
306  you first try to run the examples provided with the base version. You will    
307  probably want to run the example that is the closest to the configuration  \item \texttt{lsopt}: Line search code used for optimization.
308  you will use eventually. The examples are located in subdirectories under    
309  the directory \textit{verification} and are briefly described below (a full  \item \texttt{optim}: Interface between MITgcm and line search code.
310  description is given in section 2):    
   
 \subsection{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.  
 2D (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}  
311  \end{itemize}  \end{itemize}
312    
313  \subsection{Directory structure of model examples}  \section[Building MITgcm]{Building the code}
   
 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.  
   
 \section{Building the code}  
314  \label{sect:buildingCode}  \label{sect:buildingCode}
315    \begin{rawhtml}
316    <!-- CMIREDIR:buildingCode: -->
317    \end{rawhtml}
318    
319    To compile the code, we use the \texttt{make} program. This uses a
320    file (\texttt{Makefile}) that allows us to pre-process source files,
321    specify compiler and optimization options and also figures out any
322    file dependencies. We supply a script (\texttt{genmake2}), described
323    in section \ref{sect:genmake}, that automatically creates the
324    \texttt{Makefile} for you. You then need to build the dependencies and
325    compile the code.
326    
327    As an example, assume that you want to build and run experiment
328    \texttt{verification/exp2}. The are multiple ways and places to
329    actually do this but here let's build the code in
330    \texttt{verification/exp2/build}:
331    \begin{verbatim}
332    % cd verification/exp2/build
333    \end{verbatim}
334    First, build the \texttt{Makefile}:
335    \begin{verbatim}
336    % ../../../tools/genmake2 -mods=../code
337    \end{verbatim}
338    The command line option tells \texttt{genmake} to override model source
339    code with any files in the directory \texttt{../code/}.
340    
341    On many systems, the \texttt{genmake2} program will be able to
342    automatically recognize the hardware, find compilers and other tools
343    within the user's path (``\texttt{echo \$PATH}''), and then choose an
344    appropriate set of options from the files (``optfiles'') contained in
345    the \texttt{tools/build\_options} directory.  Under some
346    circumstances, a user may have to create a new ``optfile'' in order to
347    specify the exact combination of compiler, compiler flags, libraries,
348    and other options necessary to build a particular configuration of
349    MITgcm.  In such cases, it is generally helpful to read the existing
350    ``optfiles'' and mimic their syntax.
351    
352    Through the MITgcm-support list, the MITgcm developers are willing to
353    provide help writing or modifing ``optfiles''.  And we encourage users
354    to post new ``optfiles'' (particularly ones for new machines or
355    architectures) to the
356    \begin{rawhtml} <A href="mailto:MITgcm-support@mitgcm.org"> \end{rawhtml}
357    MITgcm-support@mitgcm.org
358    \begin{rawhtml} </A> \end{rawhtml}
359    list.
360    
361  To compile the code, we use the {\em make} program. This uses a file  To specify an optfile to \texttt{genmake2}, the syntax is:
 ({\em Makefile}) that allows us to pre-process source files, specify  
 compiler and optimization options and also figures out any file  
 dependancies. We supply a script ({\em genmake}), described in section  
 \ref{sect:genmake}, that automatically creates the {\em Makefile} for  
 you. You then need to build the dependancies and compile the code.  
   
 As an example, let's assume that you want to build and run experiment  
 \textit{verification/exp2}. The are multiple ways and places to actually  
 do this but here let's build the code in  
 \textit{verification/exp2/input}:  
 \begin{verbatim}  
 % cd verification/exp2/input  
 \end{verbatim}  
 First, build the {\em Makefile}:  
362  \begin{verbatim}  \begin{verbatim}
363  % ../../../tools/genmake -mods=../code  % ../../../tools/genmake2 -mods=../code -of /path/to/optfile
364  \end{verbatim}  \end{verbatim}
 The command line option tells {\em genmake} to override model source  
 code with any files in the directory {\em ./code/}.  
365    
366  If there is no \textit{.genmakerc} in the \textit{input} directory, you have  Once a \texttt{Makefile} has been generated, we create the
367  to use the following options when invoking \textit{genmake}:  dependencies with the command:
 \begin{verbatim}  
 % ../../../tools/genmake  -mods=../code  
 \end{verbatim}  
   
 Next, create the dependancies:  
368  \begin{verbatim}  \begin{verbatim}
369  % make depend  % make depend
370  \end{verbatim}  \end{verbatim}
371  This modifies {\em Makefile} by attaching a [long] list of files on  This modifies the \texttt{Makefile} by attaching a (usually, long)
372  which other files depend. The purpose of this is to reduce  list of files upon which other files depend. The purpose of this is to
373  re-compilation if and when you start to modify the code. {\tt make  reduce re-compilation if and when you start to modify the code. The
374  depend} also created links from the model source to this directory.  {\tt make depend} command also creates links from the model source to
375    this directory.  It is important to note that the {\tt make depend}
376    stage will occasionally produce warnings or errors since the
377    dependency parsing tool is unable to find all of the necessary header
378    files (\textit{eg.}  \texttt{netcdf.inc}).  In these circumstances, it
379    is usually OK to ignore the warnings/errors and proceed to the next
380    step.
381    
382  Now compile the code:  Next one can compile the code using:
383  \begin{verbatim}  \begin{verbatim}
384  % make  % make
385  \end{verbatim}  \end{verbatim}
386  The {\tt make} command creates an executable called \textit{mitgcmuv}.  The {\tt make} command creates an executable called \texttt{mitgcmuv}.
387    Additional make ``targets'' are defined within the makefile to aid in
388    the production of adjoint and other versions of MITgcm.  On SMP
389    (shared multi-processor) systems, the build process can often be sped
390    up appreciably using the command:
391    \begin{verbatim}
392    % make -j 2
393    \end{verbatim}
394    where the ``2'' can be replaced with a number that corresponds to the
395    number of CPUs available.
396    
397  Now you are ready to run the model. General instructions for doing so are  Now you are ready to run the model. General instructions for doing so are
398  given in section \ref{sect:runModel}. Here, we can run the model with:  given in section \ref{sect:runModel}. Here, we can run the model by
399    first creating links to all the input files:
400    \begin{verbatim}
401    ln -s ../input/* .
402    \end{verbatim}
403    and then calling the executable with:
404  \begin{verbatim}  \begin{verbatim}
405  ./mitgcmuv > output.txt  ./mitgcmuv > output.txt
406  \end{verbatim}  \end{verbatim}
407  where we are re-directing the stream of text output to the file {\em  where we are re-directing the stream of text output to the file
408  output.txt}.  \texttt{output.txt}.
   
409    
410  \subsection{Building/compiling the code elsewhere}  \subsection{Building/compiling the code elsewhere}
411    
# Line 326  executable in the {\em input} directory Line 414  executable in the {\em input} directory
414  convenience. You can also configure and compile the code in other  convenience. You can also configure and compile the code in other
415  locations, for example on a scratch disk with out having to copy the  locations, for example on a scratch disk with out having to copy the
416  entire source tree. The only requirement to do so is you have {\tt  entire source tree. The only requirement to do so is you have {\tt
417  genmake} in your path or you know the absolute path to {\tt genmake}.    genmake2} in your path or you know the absolute path to {\tt
418      genmake2}.
419    
420  The following sections outline some possible methods of organizing you  The following sections outline some possible methods of organizing
421  source and data.  your source and data.
422    
423  \subsubsection{Building from the {\em ../code directory}}  \subsubsection{Building from the {\em ../code directory}}
424    
425  This is just as simple as building in the {\em input/} directory:  This is just as simple as building in the {\em input/} directory:
426  \begin{verbatim}  \begin{verbatim}
427  % cd verification/exp2/code  % cd verification/exp2/code
428  % ../../../tools/genmake  % ../../../tools/genmake2
429  % make depend  % make depend
430  % make  % make
431  \end{verbatim}  \end{verbatim}
# Line 347  files must be in the same place. If you Line 436  files must be in the same place. If you
436  % cp ../code/mitgcmuv ./  % cp ../code/mitgcmuv ./
437  % ./mitgcmuv > output.txt  % ./mitgcmuv > output.txt
438  \end{verbatim}  \end{verbatim}
439  or if you will be making muliple runs with the same executable:  or if you will be making multiple runs with the same executable:
440  \begin{verbatim}  \begin{verbatim}
441  % cd ../  % cd ../
442  % cp -r input run1  % cp -r input run1
# Line 359  or if you will be making muliple runs wi Line 448  or if you will be making muliple runs wi
448  \subsubsection{Building from a new directory}  \subsubsection{Building from a new directory}
449    
450  Since the {\em input} directory contains input files it is often more  Since the {\em input} directory contains input files it is often more
451  useful to keep {\em input} prestine and build in a new directory  useful to keep {\em input} pristine and build in a new directory
452  within {\em verification/exp2/}:  within {\em verification/exp2/}:
453  \begin{verbatim}  \begin{verbatim}
454  % cd verification/exp2  % cd verification/exp2
455  % mkdir build  % mkdir build
456  % cd build  % cd build
457  % ../../../tools/genmake -mods=../code  % ../../../tools/genmake2 -mods=../code
458  % make depend  % make depend
459  % make  % make
460  \end{verbatim}  \end{verbatim}
# Line 387  running in a new directory each time mig Line 476  running in a new directory each time mig
476  % ./mitgcmuv > output.txt  % ./mitgcmuv > output.txt
477  \end{verbatim}  \end{verbatim}
478    
479  \subsubsection{Building from on a scratch disk}  \subsubsection{Building on a scratch disk}
480    
481  Model object files and output data can use up large amounts of disk  Model object files and output data can use up large amounts of disk
482  space so it is often the case that you will be operating on a large  space so it is often the case that you will be operating on a large
# Line 395  scratch disk. Assuming the model source Line 484  scratch disk. Assuming the model source
484  following commands will build the model in {\em /scratch/exp2-run1}:  following commands will build the model in {\em /scratch/exp2-run1}:
485  \begin{verbatim}  \begin{verbatim}
486  % cd /scratch/exp2-run1  % cd /scratch/exp2-run1
487  % ~/MITgcm/tools/genmake -rootdir=~/MITgcm -mods=~/MITgcm/verification/exp2/code  % ~/MITgcm/tools/genmake2 -rootdir=~/MITgcm \
488      -mods=~/MITgcm/verification/exp2/code
489  % make depend  % make depend
490  % make  % make
491  \end{verbatim}  \end{verbatim}
# Line 411  the one experiment: Line 501  the one experiment:
501  % cd /scratch/exp2  % cd /scratch/exp2
502  % mkdir build  % mkdir build
503  % cd build  % cd build
504  % ~/MITgcm/tools/genmake -rootdir=~/MITgcm -mods=~/MITgcm/verification/exp2/code  % ~/MITgcm/tools/genmake2 -rootdir=~/MITgcm \
505      -mods=~/MITgcm/verification/exp2/code
506  % make depend  % make depend
507  % make  % make
508  % cd ../  % cd ../
# Line 421  the one experiment: Line 512  the one experiment:
512  \end{verbatim}  \end{verbatim}
513    
514    
515    \subsection{Using \texttt{genmake2}}
 \subsection{\textit{genmake}}  
516  \label{sect:genmake}  \label{sect:genmake}
517    
518  To compile the code, use the script \textit{genmake} located in the \textit{%  To compile the code, first use the program \texttt{genmake2} (located
519  tools} directory. \textit{genmake} is a script that generates the makefile.  in the \texttt{tools} directory) to generate a Makefile.
520  It has been written so that the code can be compiled on a wide diversity of  \texttt{genmake2} is a shell script written to work with all
521  machines and systems. However, if it doesn't work the first time on your  ``sh''--compatible shells including bash v1, bash v2, and Bourne.
522  platform, you might need to edit certain lines of \textit{genmake} in the  Internally, \texttt{genmake2} determines the locations of needed
523  section containing the setups for the different machines. The file is  files, the compiler, compiler options, libraries, and Unix tools.  It
524  structured like this:  relies upon a number of ``optfiles'' located in the
525  \begin{verbatim}  \texttt{tools/build\_options} directory.
526          .  
527          .  The purpose of the optfiles is to provide all the compilation options
528          .  for particular ``platforms'' (where ``platform'' roughly means the
529  general instructions (machine independent)  combination of the hardware and the compiler) and code configurations.
530          .  Given the combinations of possible compilers and library dependencies
531          .  ({\it eg.}  MPI and NetCDF) there may be numerous optfiles available
532          .  for a single machine.  The naming scheme for the majority of the
533      - setup machine 1  optfiles shipped with the code is
534      - setup machine 2  \begin{center}
535      - setup machine 3    {\bf OS\_HARDWARE\_COMPILER }
536      - setup machine 4  \end{center}
537         etc  where
538          .  \begin{description}
539          .  \item[OS] is the name of the operating system (generally the
540          .    lower-case output of the {\tt 'uname'} command)
541  \end{verbatim}  \item[HARDWARE] is a string that describes the CPU type and
542      corresponds to output from the  {\tt 'uname -m'} command:
543  For example, the setup corresponding to a DEC alpha machine is reproduced    \begin{description}
544  here:    \item[ia32] is for ``x86'' machines such as i386, i486, i586, i686,
545  \begin{verbatim}      and athlon
546    case OSF1+mpi:    \item[ia64] is for Intel IA64 systems (eg. Itanium, Itanium2)
547      echo "Configuring for DEC Alpha"    \item[amd64] is AMD x86\_64 systems
548      set CPP        = ( '/usr/bin/cpp -P' )    \item[ppc] is for Mac PowerPC systems
549      set DEFINES    = ( ${DEFINES}  '-DTARGET_DEC -DWORDLENGTH=1' )    \end{description}
550      set KPP        = ( 'kapf' )  \item[COMPILER] is the compiler name (generally, the name of the
551      set KPPFILES   = ( 'main.F' )    FORTRAN executable)
552      set KFLAGS1    = ( '-scan=132 -noconc -cmp=' )  \end{description}
553      set FC         = ( 'f77' )  
554      set FFLAGS     = ( '-convert big_endian -r8 -extend_source -automatic -call_shared -notransform_loops -align dcommons' )  In many cases, the default optfiles are sufficient and will result in
555      set FOPTIM     = ( '-O5 -fast -tune host -inline all' )  usable Makefiles.  However, for some machines or code configurations,
556      set NOOPTFLAGS = ( '-O0' )  new ``optfiles'' must be written. To create a new optfile, it is
557      set LIBS       = ( '-lfmpi -lmpi -lkmp_osfp10 -pthread' )  generally best to start with one of the defaults and modify it to suit
558      set NOOPTFILES = ( 'barrier.F different_multiple.F external_fields_load.F')  your needs.  Like \texttt{genmake2}, the optfiles are all written
559      set RMFILES    = ( '*.p.out' )  using a simple ``sh''--compatible syntax.  While nearly all variables
560      breaksw  used within \texttt{genmake2} may be specified in the optfiles, the
561  \end{verbatim}  critical ones that should be defined are:
562    
563  Typically, these are the lines that you might need to edit to make \textit{%  \begin{description}
564  genmake} work on your platform if it doesn't work the first time. \textit{%  \item[FC] the FORTRAN compiler (executable) to use
565  genmake} understands several options that are described here:  \item[DEFINES] the command-line DEFINE options passed to the compiler
566    \item[CPP] the C pre-processor to use
567  \begin{itemize}  \item[NOOPTFLAGS] options flags for special files that should not be
568  \item -rootdir=dir    optimized
569    \end{description}
570  indicates where the model root directory is relative to the directory where  
571  you are compiling. This option is not needed if you compile in the \textit{%  For example, the optfile for a typical Red Hat Linux machine (``ia32''
572  bin} directory (which is the default compilation directory) or within the  architecture) using the GCC (g77) compiler is
573  \textit{verification} tree.  \begin{verbatim}
574    FC=g77
575  \item -mods=dir1,dir2,...  DEFINES='-D_BYTESWAPIO -DWORDLENGTH=4'
576    CPP='cpp  -traditional -P'
577  indicates the relative or absolute paths directories where the sources  NOOPTFLAGS='-O0'
578  should take precedence over the default versions (located in \textit{model},  #  For IEEE, use the "-ffloat-store" option
579  \textit{eesupp},...). Typically, this option is used when running the  if test "x$IEEE" = x ; then
580  examples, see below.      FFLAGS='-Wimplicit -Wunused -Wuninitialized'
581        FOPTIM='-O3 -malign-double -funroll-loops'
582  \item -enable=pkg1,pkg2,...  else
583        FFLAGS='-Wimplicit -Wunused -ffloat-store'
584  enables packages source code \textit{pkg1}, \textit{pkg2},... when creating      FOPTIM='-O0 -malign-double'
585  the makefile.  fi
586    \end{verbatim}
587  \item -disable=pkg1,pkg2,...  
588    If you write an optfile for an unrepresented machine or compiler, you
589  disables packages source code \textit{pkg1}, \textit{pkg2},... when creating  are strongly encouraged to submit the optfile to the MITgcm project
590  the makefile.  for inclusion.  Please send the file to the
591    \begin{rawhtml} <A href="mail-to:MITgcm-support@mitgcm.org"> \end{rawhtml}
592  \item -platform=machine  \begin{center}
593      MITgcm-support@mitgcm.org
594    \end{center}
595    \begin{rawhtml} </A> \end{rawhtml}
596    mailing list.
597    
598    In addition to the optfiles, \texttt{genmake2} supports a number of
599    helpful command-line options.  A complete list of these options can be
600    obtained from:
601    \begin{verbatim}
602    % genmake2 -h
603    \end{verbatim}
604    
605    The most important command-line options are:
606    \begin{description}
607      
608    \item[\texttt{--optfile=/PATH/FILENAME}] specifies the optfile that
609      should be used for a particular build.
610      
611      If no "optfile" is specified (either through the command line or the
612      MITGCM\_OPTFILE environment variable), genmake2 will try to make a
613      reasonable guess from the list provided in {\em
614        tools/build\_options}.  The method used for making this guess is
615      to first determine the combination of operating system and hardware
616      (eg. "linux\_ia32") and then find a working FORTRAN compiler within
617      the user's path.  When these three items have been identified,
618      genmake2 will try to find an optfile that has a matching name.
619      
620    \item[\texttt{--pdefault='PKG1 PKG2 PKG3 ...'}] specifies the default
621      set of packages to be used.  The normal order of precedence for
622      packages is as follows:
623      \begin{enumerate}
624      \item If available, the command line (\texttt{--pdefault}) settings
625        over-rule any others.
626    
627      \item Next, \texttt{genmake2} will look for a file named
628        ``\texttt{packages.conf}'' in the local directory or in any of the
629        directories specified with the \texttt{--mods} option.
630        
631      \item Finally, if neither of the above are available,
632        \texttt{genmake2} will use the \texttt{/pkg/pkg\_default} file.
633      \end{enumerate}
634      
635    \item[\texttt{--pdepend=/PATH/FILENAME}] specifies the dependency file
636      used for packages.
637      
638      If not specified, the default dependency file {\em pkg/pkg\_depend}
639      is used.  The syntax for this file is parsed on a line-by-line basis
640      where each line containes either a comment ("\#") or a simple
641      "PKGNAME1 (+|-)PKGNAME2" pairwise rule where the "+" or "-" symbol
642      specifies a "must be used with" or a "must not be used with"
643      relationship, respectively.  If no rule is specified, then it is
644      assumed that the two packages are compatible and will function
645      either with or without each other.
646      
647    \item[\texttt{--adof=/path/to/file}] specifies the "adjoint" or
648      automatic differentiation options file to be used.  The file is
649      analogous to the ``optfile'' defined above but it specifies
650      information for the AD build process.
651      
652      The default file is located in {\em
653        tools/adjoint\_options/adjoint\_default} and it defines the "TAF"
654      and "TAMC" compilers.  An alternate version is also available at
655      {\em tools/adjoint\_options/adjoint\_staf} that selects the newer
656      "STAF" compiler.  As with any compilers, it is helpful to have their
657      directories listed in your {\tt \$PATH} environment variable.
658      
659    \item[\texttt{--mods='DIR1 DIR2 DIR3 ...'}] specifies a list of
660      directories containing ``modifications''.  These directories contain
661      files with names that may (or may not) exist in the main MITgcm
662      source tree but will be overridden by any identically-named sources
663      within the ``MODS'' directories.
664      
665      The order of precedence for this "name-hiding" is as follows:
666      \begin{itemize}
667      \item ``MODS'' directories (in the order given)
668      \item Packages either explicitly specified or provided by default
669        (in the order given)
670      \item Packages included due to package dependencies (in the order
671        that that package dependencies are parsed)
672      \item The "standard dirs" (which may have been specified by the
673        ``-standarddirs'' option)
674      \end{itemize}
675      
676    \item[\texttt{--mpi}] This option enables certain MPI features (using
677      CPP \texttt{\#define}s) within the code and is necessary for MPI
678      builds (see Section \ref{sect:mpi-build}).
679      
680    \item[\texttt{--make=/path/to/gmake}] Due to the poor handling of
681      soft-links and other bugs common with the \texttt{make} versions
682      provided by commercial Unix vendors, GNU \texttt{make} (sometimes
683      called \texttt{gmake}) should be preferred.  This option provides a
684      means for specifying the make executable to be used.
685      
686    \item[\texttt{--bash=/path/to/sh}] On some (usually older UNIX)
687      machines, the ``bash'' shell is unavailable.  To run on these
688      systems, \texttt{genmake2} can be invoked using an ``sh'' (that is,
689      a Bourne, POSIX, or compatible) shell.  The syntax in these
690      circumstances is:
691      \begin{center}
692        \texttt{\%  /bin/sh genmake2 -bash=/bin/sh [...options...]}
693      \end{center}
694      where \texttt{/bin/sh} can be replaced with the full path and name
695      of the desired shell.
696    
697    \end{description}
698    
699    
700    \subsection{Building with MPI}
701    \label{sect:mpi-build}
702    
703    Building MITgcm to use MPI libraries can be complicated due to the
704    variety of different MPI implementations available, their dependencies
705    or interactions with different compilers, and their often ad-hoc
706    locations within file systems.  For these reasons, its generally a
707    good idea to start by finding and reading the documentation for your
708    machine(s) and, if necessary, seeking help from your local systems
709    administrator.
710    
711    The steps for building MITgcm with MPI support are:
712    \begin{enumerate}
713      
714    \item Determine the locations of your MPI-enabled compiler and/or MPI
715      libraries and put them into an options file as described in Section
716      \ref{sect:genmake}.  One can start with one of the examples in:
717      \begin{rawhtml} <A
718        href="http://mitgcm.org/cgi-bin/viewcvs.cgi/MITgcm/tools/build_options/">
719      \end{rawhtml}
720      \begin{center}
721        \texttt{MITgcm/tools/build\_options/}
722      \end{center}
723      \begin{rawhtml} </A> \end{rawhtml}
724      such as \texttt{linux\_ia32\_g77+mpi\_cg01} or
725      \texttt{linux\_ia64\_efc+mpi} and then edit it to suit the machine at
726      hand.  You may need help from your user guide or local systems
727      administrator to determine the exact location of the MPI libraries.
728      If libraries are not installed, MPI implementations and related
729      tools are available including:
730      \begin{itemize}
731      \item \begin{rawhtml} <A
732          href="http://www-unix.mcs.anl.gov/mpi/mpich/">
733        \end{rawhtml}
734        MPICH
735        \begin{rawhtml} </A> \end{rawhtml}
736    
737      \item \begin{rawhtml} <A
738          href="http://www.lam-mpi.org/">
739        \end{rawhtml}
740        LAM/MPI
741        \begin{rawhtml} </A> \end{rawhtml}
742    
743      \item \begin{rawhtml} <A
744          href="http://www.osc.edu/~pw/mpiexec/">
745        \end{rawhtml}
746        MPIexec
747        \begin{rawhtml} </A> \end{rawhtml}
748      \end{itemize}
749      
750    \item Build the code with the \texttt{genmake2} \texttt{-mpi} option
751      (see Section \ref{sect:genmake}) using commands such as:
752    {\footnotesize \begin{verbatim}
753      %  ../../../tools/genmake2 -mods=../code -mpi -of=YOUR_OPTFILE
754      %  make depend
755      %  make
756    \end{verbatim} }
757      
758    \item Run the code with the appropriate MPI ``run'' or ``exec''
759      program provided with your particular implementation of MPI.
760      Typical MPI packages such as MPICH will use something like:
761    \begin{verbatim}
762      %  mpirun -np 4 -machinefile mf ./mitgcmuv
763    \end{verbatim}
764      Sightly more complicated scripts may be needed for many machines
765      since execution of the code may be controlled by both the MPI
766      library and a job scheduling and queueing system such as PBS,
767      LoadLeveller, Condor, or any of a number of similar tools.  A few
768      example scripts (those used for our \begin{rawhtml} <A
769        href="http://mitgcm.org/testing.html"> \end{rawhtml}regular
770      verification runs\begin{rawhtml} </A> \end{rawhtml}) are available
771      at:
772      \begin{rawhtml} <A
773        href="http://mitgcm.org/cgi-bin/viewcvs.cgi/MITgcm_contrib/test_scripts/">
774      \end{rawhtml}
775      {\footnotesize \tt
776        http://mitgcm.org/cgi-bin/viewcvs.cgi/MITgcm\_contrib/test\_scripts/ }
777      \begin{rawhtml} </A> \end{rawhtml}
778    
779    \end{enumerate}
780    
781    An example of the above process on the MITgcm cluster (``cg01'') using
782    the GNU g77 compiler and the mpich MPI library is:
783    
784    {\footnotesize \begin{verbatim}
785      %  cd MITgcm/verification/exp5
786      %  mkdir build
787      %  cd build
788      %  ../../../tools/genmake2 -mpi -mods=../code \
789           -of=../../../tools/build_options/linux_ia32_g77+mpi_cg01
790      %  make depend
791      %  make
792      %  cd ../input
793      %  /usr/local/pkg/mpi/mpi-1.2.4..8a-gm-1.5/g77/bin/mpirun.ch_gm \
794           -machinefile mf --gm-kill 5 -v -np 2  ../build/mitgcmuv
795    \end{verbatim} }
796    
797  specifies the platform for which you want the makefile. In general, you  \section[Running MITgcm]{Running the model in prognostic mode}
 won't need this option. \textit{genmake} will select the right machine for  
 you (the one you're working on!). However, this option is useful if you have  
 a choice of several compilers on one machine and you want to use the one  
 that is not the default (ex: \texttt{pgf77} instead of \texttt{f77} under  
 Linux).  
   
 \item -mpi  
   
 this is used when you want to run the model in parallel processing mode  
 under mpi (see section on parallel computation for more details).  
   
 \item -jam  
   
 this is used when you want to run the model in parallel processing mode  
 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  
 \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}.  
   
   
 \section{Running the model}  
798  \label{sect:runModel}  \label{sect:runModel}
799    \begin{rawhtml}
800    <!-- CMIREDIR:runModel: -->
801    \end{rawhtml}
802    
803    If compilation finished succesfully (section \ref{sect:buildingCode})
804    then an executable called \texttt{mitgcmuv} will now exist in the
805    local directory.
806    
807  If compilation finished succesfuully (section \ref{sect:buildModel})  To run the model as a single process (\textit{ie.} not in parallel)
808  then an executable called {\em mitgcmuv} will now exist in the local  simply type:
 directory.  
   
 To run the model as a single process (ie. not in parallel) simply  
 type:  
809  \begin{verbatim}  \begin{verbatim}
810  % ./mitgcmuv  % ./mitgcmuv
811  \end{verbatim}  \end{verbatim}
# Line 543  do!). The above command will spew out ma Line 815  do!). The above command will spew out ma
815  your screen.  This output contains details such as parameter values as  your screen.  This output contains details such as parameter values as
816  well as diagnostics such as mean Kinetic energy, largest CFL number,  well as diagnostics such as mean Kinetic energy, largest CFL number,
817  etc. It is worth keeping this text output with the binary output so we  etc. It is worth keeping this text output with the binary output so we
818  normally re-direct the {\em stdout} stream as follows:  normally re-direct the \texttt{stdout} stream as follows:
819  \begin{verbatim}  \begin{verbatim}
820  % ./mitgcmuv > output.txt  % ./mitgcmuv > output.txt
821  \end{verbatim}  \end{verbatim}
822    In the event that the model encounters an error and stops, it is very
823  For the example experiments in {\em vericication}, an example of the  helpful to include the last few line of this \texttt{output.txt} file
824  output is kept in {\em results/output.txt} for comparison. You can compare  along with the (\texttt{stderr}) error message within any bug reports.
825  your {\em output.txt} with this one to check that the set-up works.  
826    For the example experiments in \texttt{verification}, an example of the
827    output is kept in \texttt{results/output.txt} for comparison. You can
828    compare your \texttt{output.txt} with the corresponding one for that
829    experiment to check that the set-up works.
830    
831    
832    
833  \subsection{Output files}  \subsection{Output files}
834    
835  The model produces various output files. At a minimum, the instantaneous  The model produces various output files and, when using \texttt{mnc},
836  ``state'' of the model is written out, which is made of the following files:  sometimes even directories.  Depending upon the I/O package(s)
837    selected at compile time (either \texttt{mdsio} or \texttt{mnc} or
838    both as determined by \texttt{code/packages.conf}) and the run-time
839    flags set (in \texttt{input/data.pkg}), the following output may
840    appear.
841    
842    
843    \subsubsection{MDSIO output files}
844    
845    The ``traditional'' output files are generated by the \texttt{mdsio}
846    package.  At a minimum, the instantaneous ``state'' of the model is
847    written out, which is made of the following files:
848    
849  \begin{itemize}  \begin{itemize}
850  \item \textit{U.00000nIter} - zonal component of velocity field (m/s and $>  \item \texttt{U.00000nIter} - zonal component of velocity field (m/s
851  0 $ eastward).    and positive eastward).
852    
853  \item \textit{V.00000nIter} - meridional component of velocity field (m/s  \item \texttt{V.00000nIter} - meridional component of velocity field
854  and $> 0$ northward).    (m/s and positive northward).
855    
856  \item \textit{W.00000nIter} - vertical component of velocity field (ocean:  \item \texttt{W.00000nIter} - vertical component of velocity field
857  m/s and $> 0$ upward, atmosphere: Pa/s and $> 0$ towards increasing pressure    (ocean: m/s and positive upward, atmosphere: Pa/s and positive
858  i.e. downward).    towards increasing pressure i.e. downward).
859    
860  \item \textit{T.00000nIter} - potential temperature (ocean: $^{0}$C,  \item \texttt{T.00000nIter} - potential temperature (ocean:
861  atmosphere: $^{0}$K).    $^{\circ}\mathrm{C}$, atmosphere: $^{\circ}\mathrm{K}$).
862    
863  \item \textit{S.00000nIter} - ocean: salinity (psu), atmosphere: water vapor  \item \texttt{S.00000nIter} - ocean: salinity (psu), atmosphere: water
864  (g/kg).    vapor (g/kg).
865    
866  \item \textit{Eta.00000nIter} - ocean: surface elevation (m), atmosphere:  \item \texttt{Eta.00000nIter} - ocean: surface elevation (m),
867  surface pressure anomaly (Pa).    atmosphere: surface pressure anomaly (Pa).
868  \end{itemize}  \end{itemize}
869    
870  The chain \textit{00000nIter} consists of ten figures that specify the  The chain \texttt{00000nIter} consists of ten figures that specify the
871  iteration number at which the output is written out. For example, \textit{%  iteration number at which the output is written out. For example,
872  U.0000000300} is the zonal velocity at iteration 300.  \texttt{U.0000000300} is the zonal velocity at iteration 300.
873    
874  In addition, a ``pickup'' or ``checkpoint'' file called:  In addition, a ``pickup'' or ``checkpoint'' file called:
875    
876  \begin{itemize}  \begin{itemize}
877  \item \textit{pickup.00000nIter}  \item \texttt{pickup.00000nIter}
878  \end{itemize}  \end{itemize}
879    
880  is written out. This file represents the state of the model in a condensed  is written out. This file represents the state of the model in a condensed
# Line 595  form and is used for restarting the inte Line 882  form and is used for restarting the inte
882  there is an additional ``pickup'' file:  there is an additional ``pickup'' file:
883    
884  \begin{itemize}  \begin{itemize}
885  \item \textit{pickup\_cd.00000nIter}  \item \texttt{pickup\_cd.00000nIter}
886  \end{itemize}  \end{itemize}
887    
888  containing the D-grid velocity data and that has to be written out as well  containing the D-grid velocity data and that has to be written out as well
889  in order to restart the integration. Rolling checkpoint files are the same  in order to restart the integration. Rolling checkpoint files are the same
890  as the pickup files but are named differently. Their name contain the chain  as the pickup files but are named differently. Their name contain the chain
891  \textit{ckptA} or \textit{ckptB} instead of \textit{00000nIter}. They can be  \texttt{ckptA} or \texttt{ckptB} instead of \texttt{00000nIter}. They can be
892  used to restart the model but are overwritten every other time they are  used to restart the model but are overwritten every other time they are
893  output to save disk space during long integrations.  output to save disk space during long integrations.
894    
895    \subsubsection{MNC output files}
896    
897    Unlike the \texttt{mdsio} output, the \texttt{mnc}--generated output
898    is usually (though not necessarily) placed within a subdirectory with
899    a name such as \texttt{mnc\_test\_\${DATE}\_\${SEQ}}.  
900    
901  \subsection{Looking at the output}  \subsection{Looking at the output}
902    
903  All the model data are written according to a ``meta/data'' file format.  The ``traditional'' or mdsio model data are written according to a
904  Each variable is associated with two files with suffix names \textit{.data}  ``meta/data'' file format.  Each variable is associated with two files
905  and \textit{.meta}. The \textit{.data} file contains the data written in  with suffix names \texttt{.data} and \texttt{.meta}. The
906  binary form (big\_endian by default). The \textit{.meta} file is a  \texttt{.data} file contains the data written in binary form
907  ``header'' file that contains information about the size and the structure  (big\_endian by default). The \texttt{.meta} file is a ``header'' file
908  of the \textit{.data} file. This way of organizing the output is  that contains information about the size and the structure of the
909  particularly useful when running multi-processors calculations. The base  \texttt{.data} file. This way of organizing the output is particularly
910  version of the model includes a few matlab utilities to read output files  useful when running multi-processors calculations. The base version of
911  written in this format. The matlab scripts are located in the directory  the model includes a few matlab utilities to read output files written
912  \textit{utils/matlab} under the root tree. The script \textit{rdmds.m} reads  in this format. The matlab scripts are located in the directory
913  the data. Look at the comments inside the script to see how to use it.  \texttt{utils/matlab} under the root tree. The script \texttt{rdmds.m}
914    reads the data. Look at the comments inside the script to see how to
915    use it.
916    
917  Some examples of reading and visualizing some output in {\em Matlab}:  Some examples of reading and visualizing some output in {\em Matlab}:
918  \begin{verbatim}  \begin{verbatim}
# Line 634  Some examples of reading and visualizing Line 929  Some examples of reading and visualizing
929  >> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end  >> for n=1:11; imagesc(eta(:,:,n)');axis ij;colorbar;pause(.5);end
930  \end{verbatim}  \end{verbatim}
931    
932  \section{Doing it yourself: customizing the code}  Similar scripts for netCDF output (\texttt{rdmnc.m}) are available and
933    they are described in Section \ref{sec:pkg:mnc}.
 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.  
   
 \subsection{Configuration and setup}  
   
 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.  
   
 \subsection{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}  
 \item time-discretization  
 \end{itemize}  
   
 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}.'.  
   
 \subsection{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{\ }  
   
 \subsection{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}  
 \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).  
   
 \subsection{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{%  
 hydrogThetaFile }and \textbf{hydrogSaltFile}. These files should contain 3D  
 data ordered in an (x, y, r) fashion with k=1 as the first vertical level.  
 If no file names are provided, the tracers are then initialized with the  
 values of \textbf{tRef }and \textbf{sRef }mentioned above (in the equation  
 of state section). In this case, the initial tracer data are uniform in x  
 and y for each depth level.  
   
 \begin{itemize}  
 \item forcing  
 \end{itemize}  
   
 This part is more relevant for the ocean, the procedure for the atmosphere  
 not being completely stabilized at the moment.  
   
 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).  
934    
935    The MNC output files are all in the ``self-describing'' netCDF
936    format and can thus be browsed and/or plotted using tools such as:
937  \begin{itemize}  \begin{itemize}
938  \item dissipation  \item \texttt{ncdump} is a utility which is typically included
939  \end{itemize}    with every netCDF install:
940      \begin{rawhtml} <A href="http://www.unidata.ucar.edu/packages/netcdf/"> \end{rawhtml}
941  Lateral eddy diffusivities for temperature and salinity/specific humidity  \begin{verbatim}
942  are specified through the variables \textbf{diffKhT }and \textbf{diffKhS }%  http://www.unidata.ucar.edu/packages/netcdf/
943  (in m$^{2}$/s). Vertical eddy diffusivities are specified through the  \end{verbatim}
944  variables \textbf{diffKzT }and \textbf{diffKzS }(in m$^{2}$/s) for the ocean    \begin{rawhtml} </A> \end{rawhtml} and it converts the netCDF
945  and \textbf{diffKpT }and \textbf{diffKpS }(in Pa$^{2}$/s) for the    binaries into formatted ASCII text files.
 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}  
 \item ocean convection  
 \end{itemize}  
   
 Two options are available to parameterize ocean convection: one is to use  
 the convective adjustment scheme. In this case, you need to set the variable  
 \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.  
   
 \subsection{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).  
   
 \begin{itemize}  
 \item run duration  
 \end{itemize}  
   
 The beginning of a simulation is set by specifying a start time (in s)  
 through the real variable \textbf{startTime }or by specifying an initial  
 iteration number through the integer variable \textbf{nIter0}. If these  
 variables are set to nonzero values, the model will look for a ''pickup''  
 file \textit{pickup.0000nIter0 }to restart the integration\textit{. }The end  
 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}.  
946    
947  \begin{itemize}  \item \texttt{ncview} utility is a very convenient and quick way
948  \item frequency of output    to plot netCDF data and it runs on most OSes:
949      \begin{rawhtml} <A href="http://meteora.ucsd.edu/~pierce/ncview_home_page.html"> \end{rawhtml}
950    \begin{verbatim}
951    http://meteora.ucsd.edu/~pierce/ncview_home_page.html
952    \end{verbatim}
953      \begin{rawhtml} </A> \end{rawhtml}
954      
955    \item MatLAB(c) and other common post-processing environments provide
956      various netCDF interfaces including:
957      \begin{rawhtml} <A href="http://mexcdf.sourceforge.net/"> \end{rawhtml}
958    \begin{verbatim}
959    http://mexcdf.sourceforge.net/
960    \end{verbatim}
961      \begin{rawhtml} </A> \end{rawhtml}
962      \begin{rawhtml} <A href="http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html"> \end{rawhtml}
963    \begin{verbatim}
964    http://woodshole.er.usgs.gov/staffpages/cdenham/public_html/MexCDF/nc4ml5.html
965    \end{verbatim}
966      \begin{rawhtml} </A> \end{rawhtml}
967  \end{itemize}  \end{itemize}
968    
 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{%  
 64}).  

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