/[MITgcm]/manual/s_phys_pkgs/text/exch2.tex
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revision 1.24 by molod, Mon Jul 18 20:45:27 2005 UTC revision 1.25 by edhill, Tue Aug 9 21:52:09 2005 UTC
# Line 23  into any number of tiles that divide eve Line 23  into any number of tiles that divide eve
23  dimensions of the subdomain.  Furthermore, the tiles can run on  dimensions of the subdomain.  Furthermore, the tiles can run on
24  separate processors individually or in groups, which provides for  separate processors individually or in groups, which provides for
25  manual compile-time load balancing across a relatively arbitrary  manual compile-time load balancing across a relatively arbitrary
26  number of processors. \\  number of processors.
27    
28  The exchange parameters are declared in  The exchange parameters are declared in
29  \filelink{pkg/exch2/W2\_EXCH2\_TOPOLOGY.h}{pkg-exch2-W2_EXCH2_TOPOLOGY.h}  \filelink{pkg/exch2/W2\_EXCH2\_TOPOLOGY.h}{pkg-exch2-W2_EXCH2_TOPOLOGY.h}
# Line 44  file for single-processor execution. Line 44  file for single-processor execution.
44  \subsubsection{Invoking exch2}  \subsubsection{Invoking exch2}
45    
46  To use exch2 with the cubed sphere, the following conditions must be  To use exch2 with the cubed sphere, the following conditions must be
47  met: \\  met:
48    
49  $\bullet$ The exch2 package is included when \file{genmake2} is run.  \begin{itemize}
50    The easiest way to do this is to add the line \code{exch2} to the  \item The exch2 package is included when \file{genmake2} is run.  The
51    \file{profile.conf} file -- see Section    easiest way to do this is to add the line \code{exch2} to the
52    \ref{sect:buildingCode} \sectiontitle{Building the code} for general    \file{packages.conf} file -- see Section \ref{sect:buildingCode}
53    details. \\    \sectiontitle{Building the code} for general
54      details.
55    
56  $\bullet$ An example of \file{W2\_EXCH2\_TOPOLOGY.h} and  \item An example of \file{W2\_EXCH2\_TOPOLOGY.h} and
57    \file{w2\_e2setup.F} must reside in a directory containing files    \file{w2\_e2setup.F} must reside in a directory containing files
58    symbolically linked by the \file{genmake2} script.  The safest place to    symbolically linked by the \file{genmake2} script.  The safest place
59    put these is the directory indicated in the \code{-mods=DIR} command    to put these is the directory indicated in the \code{-mods=DIR}
60    line modifier (typically \file{../code}), or the build directory.    command line modifier (typically \file{../code}), or the build
61    The default versions of these files reside in \file{pkg/exch2} and    directory.  The default versions of these files reside in
62    are linked automatically if no other versions exist elsewhere in the    \file{pkg/exch2} and are linked automatically if no other versions
63    build path, but they should be left untouched to avoid breaking    exist elsewhere in the build path, but they should be left untouched
64    configurations other than the one you intend to modify.\\    to avoid breaking configurations other than the one you intend to
65      modify.
66  $\bullet$ Files containing grid parameters, named  
67    \file{tile00$n$.mitgrid} where $n$=\code{(1:6)} (one per subdomain),  \item Files containing grid parameters, named \file{tile00$n$.mitgrid}
68    must be in the working directory when the MITgcm executable is run.    where $n$=\code{(1:6)} (one per subdomain), must be in the working
69    These files are provided in the example experiments for cubed sphere    directory when the MITgcm executable is run.  These files are
70    configurations with 32$\times$32 cube sides    provided in the example experiments for cubed sphere configurations
71    -- please contact MITgcm support if you want to generate    with 32$\times$32 cube sides -- please contact MITgcm support if you
72    files for other configurations. \\    want to generate files for other configurations.
73    
74  $\bullet$ As always when compiling MITgcm, the file \file{SIZE.h} must  \item As always when compiling MITgcm, the file \file{SIZE.h} must be
75    be placed where \file{genmake2} will find it.  In particular for    placed where \file{genmake2} will find it.  In particular for exch2,
76    exch2, the domain decomposition specified in \file{SIZE.h} must    the domain decomposition specified in \file{SIZE.h} must correspond
77    correspond with the particular configuration's topology specified in    with the particular configuration's topology specified in
78    \file{W2\_EXCH2\_TOPOLOGY.h} and \file{w2\_e2setup.F}.  Domain    \file{W2\_EXCH2\_TOPOLOGY.h} and \file{w2\_e2setup.F}.  Domain
79    decomposition issues particular to exch2 are addressed in Section    decomposition issues particular to exch2 are addressed in Section
80    \ref{sec:topogen} \sectiontitle{Generating Topology Files for exch2}    \ref{sec:topogen} \sectiontitle{Generating Topology Files for exch2}
81    and \ref{sec:exch2mpi} \sectiontitle{exch2, SIZE.h, and Multiprocessing}; a more    and \ref{sec:exch2mpi} \sectiontitle{exch2, SIZE.h, and
82    general background on the subject relevant to MITgcm is presented in      Multiprocessing}; a more general background on the subject
83    Section \ref{sect:specifying_a_decomposition}    relevant to MITgcm is presented in Section
84    \sectiontitle{Specifying a decomposition}.\\    \ref{sect:specifying_a_decomposition}
85      \sectiontitle{Specifying a decomposition}.
86    \end{itemize}
87    
88  At the time of this writing the following examples use exch2 and may  At the time of this writing the following examples use exch2 and may
89  be used for guidance:  be used for guidance:
# Line 188  by their tile number in the topology, se Line 191  by their tile number in the topology, se
191  Once the topology configuration files are created, the Fortran  Once the topology configuration files are created, the Fortran
192  \code{PARAMETER}s in \file{SIZE.h} must be configured to match.  \code{PARAMETER}s in \file{SIZE.h} must be configured to match.
193  Section \ref{sect:specifying_a_decomposition} \sectiontitle{Specifying  Section \ref{sect:specifying_a_decomposition} \sectiontitle{Specifying
194  a decomposition} provides a general description of domain    a decomposition} provides a general description of domain
195  decomposition within MITgcm and its relation to \file{SIZE.h}. The  decomposition within MITgcm and its relation to \file{SIZE.h}. The
196  current section specifies constraints that the exch2 package  current section specifies constraints that the exch2 package imposes
197  imposes and describes how to enable parallel execution with  and describes how to enable parallel execution with MPI.
 MPI. \\  
198    
199  As in the general case, the parameters \varlink{sNx}{sNx} and  As in the general case, the parameters \varlink{sNx}{sNx} and
200  \varlink{sNy}{sNy} define the size of the individual tiles, and so  \varlink{sNy}{sNy} define the size of the individual tiles, and so
201  must be assigned the same respective values as \code{tnx} and  must be assigned the same respective values as \code{tnx} and
202  \code{tny} in \file{driver.m}.\\  \code{tny} in \file{driver.m}.
203    
204  The halo width parameters \varlink{OLx}{OLx} and \varlink{OLy}{OLy}  The halo width parameters \varlink{OLx}{OLx} and \varlink{OLy}{OLy}
205  have no special bearing on exch2 and may be assigned as in the general  have no special bearing on exch2 and may be assigned as in the general
206  case. The same holds for \varlink{Nr}{Nr}, the number of vertical  case. The same holds for \varlink{Nr}{Nr}, the number of vertical
207  levels in the model.\\  levels in the model.
208    
209  The parameters \varlink{nSx}{nSx}, \varlink{nSy}{nSy},  The parameters \varlink{nSx}{nSx}, \varlink{nSy}{nSy},
210  \varlink{nPx}{nPx}, and \varlink{nPy}{nPy} relate to the number of  \varlink{nPx}{nPx}, and \varlink{nPy}{nPy} relate to the number of
# Line 210  tiles and how they are distributed on pr Line 212  tiles and how they are distributed on pr
212  the tiles are stored in the $x$ dimension, and so  the tiles are stored in the $x$ dimension, and so
213  \code{\varlink{nSy}{nSy}=1} in all cases.  Since the tiles as  \code{\varlink{nSy}{nSy}=1} in all cases.  Since the tiles as
214  configured by exch2 cannot be split up accross processors without  configured by exch2 cannot be split up accross processors without
215  regenerating the topology, \code{\varlink{nPy}{nPy}=1} as well. \\  regenerating the topology, \code{\varlink{nPy}{nPy}=1} as well.
216    
217  The number of tiles MITgcm allocates and how they are distributed  The number of tiles MITgcm allocates and how they are distributed
218  between processors depends on \varlink{nPx}{nPx} and  between processors depends on \varlink{nPx}{nPx} and
# Line 227  thirty-six tiles that allows you to excl Line 229  thirty-six tiles that allows you to excl
229  distribute the remaining twenty-nine tiles among five processors, you  distribute the remaining twenty-nine tiles among five processors, you
230  would have to run one ``dummy'' tile to make an even six tiles per  would have to run one ``dummy'' tile to make an even six tiles per
231  processor.  Such dummy tiles are \emph{not} listed in  processor.  Such dummy tiles are \emph{not} listed in
232  \file{blanklist.txt}.\\  \file{blanklist.txt}.
   
233    
234  The following is an example of \file{SIZE.h} for the twelve-tile  The following is an example of \file{SIZE.h} for the twelve-tile
235  configuration illustrated in figure \ref{fig:12tile} running on  configuration illustrated in figure \ref{fig:12tile} running on one
236  one processor: \\  processor:
237    
238  \begin{verbatim}  \begin{verbatim}
239        PARAMETER (        PARAMETER (
# Line 268  figure \ref{fig:24tile} running on six p Line 269  figure \ref{fig:24tile} running on six p
269  \end{verbatim}  \end{verbatim}
270    
271    
   
   
   
272  \subsubsection{Key Variables}  \subsubsection{Key Variables}
273    
274  The descriptions of the variables are divided up into scalars,  The descriptions of the variables are divided up into scalars,
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