/[MITgcm]/manual/s_software/text/sarch.tex

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-revision 1.7 by cnh,
Thu Feb 28 19:32:20 2002 UTC
+revision 1.13 by afe,
Wed Jan 28 20:27:54 2004 UTC
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 This chapter focuses on describing the {
  both the core numerics and the pluggable packages operate. The description
  presented here is intended to be a detailed exposition and contains significant
  background material, as well as advanced details on working with the WRAPPER.
- The tutorial sections of this manual (see Chapters
+ The tutorial sections of this manual (see sections
- \ref{chap:tutorialI}, \ref{chap:tutorialII} and \ref{chap:tutorialIII})
+ \ref{sect:tutorials}  and \ref{sect:tutorialIII})
  contain more succinct, step-by-step instructions on running basic numerical
  experiments, of varous types, both sequentially and in parallel. For many
  projects simply starting from an example code and adapting it to suit a
 Line 97 
 and operating systems. This allows numer
  \resizebox{!}{4.5in}{\includegraphics{part4/fit_in_wrapper.eps}}
  \end{center}
  \caption{
- Numerical code is written too fit within a software support
+ Numerical code is written to fit within a software support
  infrastructure called WRAPPER. The WRAPPER is portable and
  can be specialized for a wide range of specific target hardware and
  programming environments, without impacting numerical code that fits
 Line 120 
 uniprocessor and multi-processor Sun sys
  (UMA) and non-uniform memory access (NUMA) designs. Significant work has also
  been undertaken on x86 cluster systems, Alpha processor based clustered SMP
  systems, and on cache-coherent NUMA (CC-NUMA) systems from Silicon Graphics.
- The MITgcm code, operating within the WRAPPER, is also used routinely used on
+ The MITgcm code, operating within the WRAPPER, is also routinely used on
  large scale MPP systems (for example T3E systems and IBM SP systems). In all
  cases numerical code, operating within the WRAPPER, performs and scales very
  competitively with equivalent numerical code that has been modified to contain
 Line 661 
 Within a {\em bi}, {\em bj} loop
  computation is performed concurrently over as many processes and threads
  as there are physical processors available to compute.
+ An exception to the the use of {\em bi} and {\em bj} in loops arises in the
+ exchange routines used when the exch2 package is used with the cubed
+ sphere.  In this case {\em bj} is generally set to 1 and the loop runs from
+,{\em bi}.  Within the loop {\em bi} is used to retrieve the tile number,
+ which is then used to reference exchange parameters.
  The amount of computation that can be embedded
  a single loop over {\em bi} and {\em bj} varies for different parts of the
  MITgcm algorithm. Figure \ref{fig:bibj_extract} shows a code extract
-Line 781 
 The global domain size is again ninety g
+Line 787 
 The global domain size is again ninety g
  forty grid points in y. The two sub-domains in each process will be computed
  sequentially if they are given to a single thread within a single process.
  Alternatively if the code is invoked with multiple threads per process
- the two domains in y may be computed on concurrently.
+ the two domains in y may be computed concurrently.
  \item
  \begin{verbatim}
        PARAMETER (
-Line 817 
 by the application code. The startup cal
+Line 823 
 by the application code. The startup cal
  WRAPPER is shown in figure \ref{fig:wrapper_startup}.
  \begin{figure}
+ {\footnotesize
  \begin{verbatim}
         MAIN
-Line 845 
 WRAPPER is shown in figure \ref{fig:wrap
+Line 852 
 WRAPPER is shown in figure \ref{fig:wrap
  \end{verbatim}
+ }
  \caption{Main stages of the WRAPPER startup procedure.
  This process proceeds transfer of control to application code, which
  occurs through the procedure {\em THE\_MODEL\_MAIN()}.
-Line 927 
 File: {\em eesupp/inc/MAIN\_PDIRECTIVES1
+Line 935 
 File: {\em eesupp/inc/MAIN\_PDIRECTIVES1
  File: {\em eesupp/inc/MAIN\_PDIRECTIVES2.h}\\
  File: {\em model/src/THE\_MODEL\_MAIN.F}\\
  File: {\em eesupp/src/MAIN.F}\\
- File: {\em tools/genmake}\\
+ File: {\em tools/genmake2}\\
  File: {\em eedata}\\
  CPP:  {\em TARGET\_SUN}\\
  CPP:  {\em TARGET\_DEC}\\
-Line 966 
 critical communication. However, in orde
+Line 974 
 critical communication. However, in orde
  of controlling and coordinating the start up of a large number
  (hundreds and possibly even thousands) of copies of the same
  program, MPI is used. The calls to the MPI multi-process startup
- routines must be activated at compile time. This is done
+ routines must be activated at compile time.  Currently MPI libraries are
- by setting the {\em ALLOW\_USE\_MPI} and {\em ALWAYS\_USE\_MPI}
+ invoked by
- flags in the {\em CPP\_EEOPTIONS.h} file.\\
+ specifying the appropriate options file with the
+ \begin{verbatim}-of\end{verbatim} flag when running the {\em genmake2}
+ script, which generates the Makefile for compiling and linking MITgcm.
+ (Previously this was done by setting the {\em ALLOW\_USE\_MPI} and
+ {\em ALWAYS\_USE\_MPI} flags in the {\em CPP\_EEOPTIONS.h} file.)  More
+ detailed information about the use of {\em genmake2} for specifying
+ local compiler flags is located in section 3 ??\\
- \fbox{
- \begin{minipage}{4.75in}
- File: {\em eesupp/inc/CPP\_EEOPTIONS.h}\\
- CPP:  {\em ALLOW\_USE\_MPI}\\
- CPP:  {\em ALWAYS\_USE\_MPI}\\
- Parameter:  {\em nPx}\\
- Parameter:  {\em nPy}
- \end{minipage}
- } \\
- Additionally, compile time options are required to link in the
- MPI libraries and header files. Examples of these options
- can be found in the {\em genmake} script that creates makefiles
- for compilation. When this script is executed with the {bf -mpi}
- flag it will generate a makefile that includes
- paths for search for MPI head files and for linking in
- MPI libraries. For example the {\bf -mpi} flag on a
-  Silicon Graphics IRIX system causes a
- Makefile with the compilation command
- Graphics IRIX system \begin{verbatim}
- mpif77 -I/usr/local/mpi/include -DALLOW_USE_MPI -DALWAYS_USE_MPI
- \end{verbatim}
- to be generated.
- This is the correct set of options for using the MPICH open-source
- version of MPI, when it has been installed under the subdirectory
- /usr/local/mpi.
- However, on many systems there may be several
- versions of MPI installed. For example many systems have both
- the open source MPICH set of libraries and a vendor specific native form
- of the MPI libraries. The correct setup to use will depend on the
- local configuration of your system.\\
  \fbox{
  \begin{minipage}{4.75in}
- File: {\em tools/genmake}
+ File: {\em tools/genmake2}
  \end{minipage}
  } \\
  \paragraph{\bf Execution} The mechanics of starting a program in
-Line 1081 
 are also set in this routine. These are
+Line 1064 
 are also set in this routine. These are
  processes holding tiles to the west, east, south and north
  of this process. These values are stored in global storage
  in the header file {\em EESUPPORT.h} for use by
- communication routines.
+ communication routines.  The above does not hold when the
+ exch2 package is used -- exch2 sets its own parameters to
+ specify the global indices of tiles and their relationships
+ to each other.
  \\
  \fbox{
-Line 1424 
 sequence shown in section \ref{sect:call
+Line 1410 
 sequence shown in section \ref{sect:call
  WRAPPER layer.
+ {\footnotesize
  \begin{verbatim}
         MAIN
-Line 1451 
 WRAPPER layer.
+Line 1438 
 WRAPPER layer.
         |--THE_MODEL_MAIN   :: Numerical code top-level driver routine
  \end{verbatim}
+ }
  Core equations plus packages.
+ {\footnotesize
  \begin{verbatim}
  C
  C
-Line 1792 
 C    |-COMM_STATS     :: Summarise inter
+Line 1781 
 C    |-COMM_STATS     :: Summarise inter
  C                     :: events.
  C
  \end{verbatim}
+ }
  \subsection{Measuring and Characterizing Performance}

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