/[MITgcm]/manual/s_software/text/sarch.tex
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revision 1.13 by afe, Wed Jan 28 20:27:54 2004 UTC revision 1.20 by edhill, Sat Oct 16 03:40:16 2004 UTC
# Line 17  details of the MITgcm implementation and Line 17  details of the MITgcm implementation and
17  features that are employed.  features that are employed.
18    
19  \section{Overall architectural goals}  \section{Overall architectural goals}
20    \begin{rawhtml}
21    <!-- CMIREDIR:overall_architectural_goals: -->
22    \end{rawhtml}
23    
24  Broadly, the goals of the software architecture employed in MITgcm are  Broadly, the goals of the software architecture employed in MITgcm are
25  three-fold  three-fold
# Line 76  floating point operations.} Line 79  floating point operations.}
79  \end{figure}  \end{figure}
80    
81  \section{WRAPPER}  \section{WRAPPER}
82    \begin{rawhtml}
83    <!-- CMIREDIR:wrapper: -->
84    \end{rawhtml}
85    
86  A significant element of the software architecture utilized in  A significant element of the software architecture utilized in
87  MITgcm is a software superstructure and substructure collectively  MITgcm is a software superstructure and substructure collectively
# Line 150  easily be specialized to fit, in a compu Line 156  easily be specialized to fit, in a compu
156  computer architecture currently available to the scientific computing community.  computer architecture currently available to the scientific computing community.
157    
158  \subsection{Machine model parallelism}  \subsection{Machine model parallelism}
159    \begin{rawhtml}
160    <!-- CMIREDIR:domain_decomp: -->
161    \end{rawhtml}
162    
163   Codes operating under the WRAPPER target an abstract machine that is assumed to   Codes operating under the WRAPPER target an abstract machine that is assumed to
164  consist of one or more logical processors that can compute concurrently.    consist of one or more logical processors that can compute concurrently.  
# Line 537  of almost all successful scientific comp Line 546  of almost all successful scientific comp
546  last 50 years.  last 50 years.
547    
548  \section{Using the WRAPPER}  \section{Using the WRAPPER}
549    \begin{rawhtml}
550    <!-- CMIREDIR:using_the_wrapper: -->
551    \end{rawhtml}
552    
553  In order to support maximum portability the WRAPPER is implemented primarily  In order to support maximum portability the WRAPPER is implemented primarily
554  in sequential Fortran 77. At a practical level the key steps provided by the  in sequential Fortran 77. At a practical level the key steps provided by the
# Line 977  program, MPI is used. The calls to the M Line 989  program, MPI is used. The calls to the M
989  routines must be activated at compile time.  Currently MPI libraries are  routines must be activated at compile time.  Currently MPI libraries are
990  invoked by  invoked by
991  specifying the appropriate options file with the  specifying the appropriate options file with the
992  \begin{verbatim}-of\end{verbatim} flag when running the {\em genmake2}  {\tt-of} flag when running the {\em genmake2}
993  script, which generates the Makefile for compiling and linking MITgcm.  script, which generates the Makefile for compiling and linking MITgcm.
994  (Previously this was done by setting the {\em ALLOW\_USE\_MPI} and  (Previously this was done by setting the {\em ALLOW\_USE\_MPI} and
995  {\em ALWAYS\_USE\_MPI} flags in the {\em CPP\_EEOPTIONS.h} file.)  More  {\em ALWAYS\_USE\_MPI} flags in the {\em CPP\_EEOPTIONS.h} file.)  More
996  detailed information about the use of {\em genmake2} for specifying  detailed information about the use of {\em genmake2} for specifying
997  local compiler flags is located in section 3 ??\\    local compiler flags is located in section \ref{sect:genmake}.\\  
998    
999    
1000  \fbox{  \fbox{
1001  \begin{minipage}{4.75in}  \begin{minipage}{4.75in}
1002    Directory: {\em tools/build\_options}\\
1003  File: {\em tools/genmake2}  File: {\em tools/genmake2}
1004  \end{minipage}  \end{minipage}
1005  } \\  } \\
# Line 1005  product of the processor grid settings o Line 1018  product of the processor grid settings o
1018  in the file {\em SIZE.h}. The parameter {\em mf} specifies that a text file  in the file {\em SIZE.h}. The parameter {\em mf} specifies that a text file
1019  called ``mf'' will be read to get a list of processor names on  called ``mf'' will be read to get a list of processor names on
1020  which the sixty-four processes will execute. The syntax of this file  which the sixty-four processes will execute. The syntax of this file
1021  is specified by the MPI distribution  is specified by the MPI distribution.
1022  \\  \\
1023    
1024  \fbox{  \fbox{
# Line 1056  to processor identification are are used Line 1069  to processor identification are are used
1069  Allocation of processes to tiles in controlled by the routine  Allocation of processes to tiles in controlled by the routine
1070  {\em INI\_PROCS()}. For each process this routine sets  {\em INI\_PROCS()}. For each process this routine sets
1071  the variables {\em myXGlobalLo} and {\em myYGlobalLo}.  the variables {\em myXGlobalLo} and {\em myYGlobalLo}.
1072  These variables specify (in index space) the coordinate  These variables specify in index space the coordinates
1073  of the southern most and western most corner of the  of the southernmost and westernmost corner of the
1074  southern most and western most tile owned by this process.  southernmost and westernmost tile owned by this process.
1075  The variables {\em pidW}, {\em pidE}, {\em pidS} and {\em pidN}  The variables {\em pidW}, {\em pidE}, {\em pidS} and {\em pidN}
1076  are also set in this routine. These are used to identify  are also set in this routine. These are used to identify
1077  processes holding tiles to the west, east, south and north  processes holding tiles to the west, east, south and north
# Line 1067  in the header file {\em EESUPPORT.h} for Line 1080  in the header file {\em EESUPPORT.h} for
1080  communication routines.  The above does not hold when the  communication routines.  The above does not hold when the
1081  exch2 package is used -- exch2 sets its own parameters to  exch2 package is used -- exch2 sets its own parameters to
1082  specify the global indices of tiles and their relationships  specify the global indices of tiles and their relationships
1083  to each other.  to each other.  See the documentation on the exch2 package
1084    (\ref{sec:exch2})  for
1085    details.
1086  \\  \\
1087    
1088  \fbox{  \fbox{
# Line 1093  operations and that can be customized fo Line 1108  operations and that can be customized fo
1108  describes the information that is held and used.  describes the information that is held and used.
1109    
1110  \begin{enumerate}  \begin{enumerate}
1111  \item {\bf Tile-tile connectivity information} For each tile the WRAPPER  \item {\bf Tile-tile connectivity information}
1112  sets a flag that sets the tile number to the north, south, east and  For each tile the WRAPPER
1113    sets a flag that sets the tile number to the north,
1114    south, east and
1115  west of that tile. This number is unique over all tiles in a  west of that tile. This number is unique over all tiles in a
1116  configuration. The number is held in the variables {\em tileNo}  configuration. Except when using the cubed sphere and the exch2 package,
1117    the number is held in the variables {\em tileNo}
1118  ( this holds the tiles own number), {\em tileNoN}, {\em tileNoS},  ( this holds the tiles own number), {\em tileNoN}, {\em tileNoS},
1119  {\em tileNoE} and {\em tileNoW}. A parameter is also stored with each tile  {\em tileNoE} and {\em tileNoW}. A parameter is also stored with each tile
1120  that specifies the type of communication that is used between tiles.  that specifies the type of communication that is used between tiles.
# Line 1119  of the WRAPPER exchange primitive Line 1137  of the WRAPPER exchange primitive
1137  (see figure \ref{fig:communication_primitives}). The routine  (see figure \ref{fig:communication_primitives}). The routine
1138  {\em ini\_communication\_patterns()} is responsible for setting the  {\em ini\_communication\_patterns()} is responsible for setting the
1139  communication mode values for each tile.  communication mode values for each tile.
1140  \\  
1141    When using the cubed sphere configuration with the exch2 package, the
1142    relationships between tiles and their communication methods are set
1143    by the package in other variables.  See the exch2 package documentation
1144    (\ref{sec:exch2} for details.
1145    
1146    
1147    
1148  \fbox{  \fbox{
1149  \begin{minipage}{4.75in}  \begin{minipage}{4.75in}
# Line 1255  The \_EXCH operation is also central to Line 1279  The \_EXCH operation is also central to
1279  the cube-sphere grid. In this class of grid a rotation may be required  the cube-sphere grid. In this class of grid a rotation may be required
1280  between tiles. Aligning the coordinate requiring rotation with the  between tiles. Aligning the coordinate requiring rotation with the
1281  tile decomposition, allows the coordinate transformation to  tile decomposition, allows the coordinate transformation to
1282  be embedded within a custom form of the \_EXCH primitive.  be embedded within a custom form of the \_EXCH primitive.  In these
1283    cases \_EXCH is mapped to exch2 routines, as detailed in the exch2
1284    package documentation  \ref{sec:exch2}.
1285    
1286  \item {\bf Reverse Mode}  \item {\bf Reverse Mode}
1287  The communication primitives \_EXCH and \_GSUM both employ  The communication primitives \_EXCH and \_GSUM both employ
# Line 1272  operations. However, the routine argumen Line 1298  operations. However, the routine argumen
1298  is set to the value {\em REVERSE\_SIMULATION}. This signifies  is set to the value {\em REVERSE\_SIMULATION}. This signifies
1299  ti the low-level routines that the adjoint forms of the  ti the low-level routines that the adjoint forms of the
1300  appropriate communication operation should be performed.  appropriate communication operation should be performed.
1301    
1302  \item {\bf MAX\_NO\_THREADS}  \item {\bf MAX\_NO\_THREADS}
1303  The variable {\em MAX\_NO\_THREADS} is used to indicate the  The variable {\em MAX\_NO\_THREADS} is used to indicate the
1304  maximum number of OS threads that a code will use. This  maximum number of OS threads that a code will use. This
# Line 1376  a series of template files, for example Line 1403  a series of template files, for example
1403  This is done to allow a large number of variations on the exchange  This is done to allow a large number of variations on the exchange
1404  process to be maintained. One set of variations supports the  process to be maintained. One set of variations supports the
1405  cube sphere grid. Support for a cube sphere grid in MITgcm is based  cube sphere grid. Support for a cube sphere grid in MITgcm is based
1406  on having each face of the cube as a separate tile (or tiles).  on having each face of the cube as a separate tile or tiles.
1407  The exchange routines are then able to absorb much of the  The exchange routines are then able to absorb much of the
1408  detailed rotation and reorientation required when moving around the  detailed rotation and reorientation required when moving around the
1409  cube grid. The set of {\em \_EXCH} routines that contain the  cube grid. The set of {\em \_EXCH} routines that contain the
# Line 1400  quantities at the C-grid vorticity point Line 1427  quantities at the C-grid vorticity point
1427    
1428    
1429  \section{MITgcm execution under WRAPPER}  \section{MITgcm execution under WRAPPER}
1430    \begin{rawhtml}
1431    <!-- CMIREDIR:mitgcm_wrapper: -->
1432    \end{rawhtml}
1433    
1434  Fitting together the WRAPPER elements, package elements and  Fitting together the WRAPPER elements, package elements and
1435  MITgcm core equation elements of the source code produces calling  MITgcm core equation elements of the source code produces calling

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