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32 lines
1.6 KiB
32 lines
1.6 KiB
2 years ago
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\chapter{Implementation of \exo{} with \code{NetCDF}}\label{app:efficiency}
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\section{Description}
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The \code{NetCDF} software is an I/O library, callable from C or
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Fortran, which stores and retrieves scientific data structures in
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self-describing, machine-independent files. \em{Self-describing} means
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that a file includes information defining the data it
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contains. \em{Machine-independent} means that a file is represented in
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a form that can be accessed by computers with different ways of
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storing integers, characters, and floating-point numbers. It is
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available via the web from \url{https://github.com/Unidata/netcdf-c}. The
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current version is 4.9.2.
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EXODUS uses the standard \code{netCDF} distribution with no modifications.
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\section{Efficiency Issues}
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There are some efficiency concerns with using \code{NetCDF} as the low level
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data handler. The main one is that whenever a new object is
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introduced, the file is put into \em{define} mode, the new object is
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defined, and then the file is taken out of \em{define} mode. A result
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of going in and out of \em{define} mode is that all of the data that
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was output previous to the introduction of the new object is copied to
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a new file. Obviously, this copying of data to a new file is very
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inefficient. We have attempted to minimize the number of times the
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data file is put into \em{define} mode by accumulating objects within
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a single EXODUS API function. Thus using optional features such as
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the element variable truth table, concatenated node and side sets, and
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writing all property array names with \cfuncref{ex_put_prop_names} will
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increase efficiency significantly.
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