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%% * Introduction |
\section{NetCDF I/O Integration} |
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%% o what it does, citations (refs go into mitgcm_manual.bib, |
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%% o Equations |
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%% * Key subroutines and parameters |
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\section{MNC: the MITgcm NetCDF Package} |
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\label{sec:pkg:mnc} |
\label{sec:pkg:mnc} |
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\subsection{Introduction} |
The \texttt{mnc} package is a set of convenience routines written to |
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expedite the process of creating, appending, and reading NetCDF files. |
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NetCDF is an increasingly popular self-describing file format |
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\cite{rew:97} intended primarily for scientific data sets. An |
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extensive collection of NetCDF reference papers, user guides, |
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software, FAQs, and other information can be obtained from UCAR's web |
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site at: |
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\begin{rawhtml} <A href="http://www.unidata.ucar.edu/packages/netcdf/"> \end{rawhtml} |
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\begin{verbatim} |
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http://www.unidata.ucar.edu/packages/netcdf/ |
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\end{verbatim} |
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\begin{rawhtml} </A> \end{rawhtml} |
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The MNC package is a set of convenience routines written to expedite |
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the process of creating, appending, and reading NetCDF files. NetCDF |
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is a self-describing file format \cite{rew:97} intended primarily for |
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scientific data. NetCDF reference papers, user guides, FAQs, and other |
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information can be obtained from UCAR's web site at: |
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\begin{itemize} |
\subsection{Introduction} |
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\item http://www.unidata.ucar.edu/packages/netcdf/ |
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\end{itemize} |
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The \texttt{mnc} package is a two-level convenience library (or |
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``wrapper'') for most of the NetCDF Fortran API. Its purpose is to |
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streamline the user interface to NetCDF by maintaining internal |
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relations (``look-up tables'') keyed with strings (or ``names'') and |
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entities such as NetCDF files, variables, and attributes. |
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The two levels of the \texttt{mnc} package are: |
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\begin{description} |
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\item[Upper level] \ |
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The upper level contains information about two kinds of |
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associations: |
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\begin{description} |
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\item[Grid type] is lookup table indexed with a grid type name. |
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Each grid type name is associated with a number of dimensions, the |
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dimension sizes (one of which may be unlimited), and starting and |
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ending index arrays. The intent is to store all the necessary |
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size and shape information for the Fortran arrays containing |
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MITgcm--style ``tile'' variables (that is, a central region |
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surrounded by a variably-sized ``halo'' or exchange region as |
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shown in Figures \ref{fig:communication_primitives} and |
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\ref{fig:tiling-strategy}). |
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\item[Variable type] is a lookup table indexed by a variable type |
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name. For each name, the table contains a reference to a grid |
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type for the variable and the names and values of various |
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attributes. |
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\end{description} |
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Within the upper level, these associations are not permanently tied |
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to any particular NetCDF file. This allows the information to be |
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re-used over multiple file reads and writes. |
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\item[Lower level] \ |
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In the lower (or internal) level, associations are stored for NetCDF |
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files and many of the entities that they contain including |
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dimensions, variables, and global attributes. All associations are |
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on a per-file basis. Thus, each entity is tied to a unique NetCDF |
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file and will be created or destroyed when files are, respectively, |
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opened or closed. |
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\end{description} |
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\subsection{Key subroutines, parameters and files} |
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\subsection{Key Routines} |
All of the variables used to implement the lookup tables are described |
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in \filelink{pkg/mnc/mnc\_common.h}{pkg/mnc/mnc_common.h}. |
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\subsection{References} |
\subsection{Package Reference} |
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