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<html>
<head>
<title>
SPARSE_DISPLAY - Sparsity Pattern of a Matrix
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
SPARSE_DISPLAY <br> Sparsity Pattern of a Matrix
</h1>
<hr>
<p>
<b>SPARSE_DISPLAY</b>
is a C++ library which
can read information defining a matrix of numbers and display
the sparsity pattern or location of the nonzero elements using
gnuplot. This operation is already available in the built-in
MATLAB "spy" command.
</p>
<p>
The user can call "spy_ge" and pass in a matrix, in general (GE) format;
the routine will then locate the nonzero entries, and write out a
data file and a command file which together can be used to instruct
gnuplot to create a sparsity plot.
</p>
<p>
If the user already has a file containing a list of pairs of indices
(I,J) corresponding to nonzero matrix entries, then the user can call
"spy_file", which will write out a command file only. Together, the
user data file and the command file can be used to instruct
gnuplot to create a sparsity plot.
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files made available on this
web page are distributed under
<a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
</p>
<h3 align = "center">
Languages:
</h3>
<p>
<b>SPARSE_DISPLAY</b> is available in
<a href = "../../c_src/sparse_display/sparse_display.html">a C version</a> and
<a href = "../../cpp_src/sparse_display/sparse_display.html">a C++ version</a> and
<a href = "../../f77_src/sparse_display/sparse_display.html">a FORTRAN77 version</a> and
<a href = "../../f_src/sparse_display/sparse_display.html">a FORTRAN90 version</a> and
<a href = "../../m_src/sparse_display/sparse_display.html">a MATLAB version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../cpp_src/cg/cg.html">
CG</a>,
a C++ library which
implements a simple version of the conjugate gradient (CG) method
for solving a system of linear equations of the form A*x=b,
suitable for situations in which the matrix A is positive definite
(only real, positive eigenvalues) and symmetric.
</p>
<p>
<a href = "../../cpp_src/gnuplot/gnuplot.html">
GNUPLOT</a>,
C++ programs which
illustrate how a program can write data and command files
so that gnuplot can create plots of the program results.
</p>
<p>
<a href = "../../cpp_src/mm_io/mm_io.html">
MM_IO</a>,
a C++ library which
reads and writes sparse linear systems stored in the Matrix Market (MM)
format.
</p>
<p>
<a href = "../../cpp_src/wathen/wathen.html">
WATHEN</a>,
a C++ library which
compares storage schemes (full, banded, sparse triplet) and
solution strategies (Linpack full, Linpack banded,
conjugate gradient (CG)) for linear systems involving the Wathen matrix,
which can arise when solving a problem using the
finite element method (FEM).
</p>
<h3 align = "center">
Source Code:
</h3>
<p>
<ul>
<li>
<a href = "sparse_display.cpp">sparse_display.cpp</a>, the source code.
</li>
<li>
<a href = "sparse_display.hpp">sparse_display.hpp</a>, the include file.
</li>
<li>
<a href = "sparse_display.sh">sparse_display.sh</a>,
BASH commands to compile the source code.
</li>
</ul>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<ul>
<li>
<a href = "sparse_display_prb.cpp">sparse_display_prb.cpp</a>,
a sample calling program.
</li>
<li>
<a href = "sparse_display_prb.sh">sparse_display_prb.sh</a>,
BASH commands to compile and run the sample program.
</li>
<li>
<a href = "sparse_display_prb_output.txt">sparse_display_prb_output.txt</a>,
the output file.
</li>
<li>
<a href = "wathen_ge_data.txt">wathen_ge_data.txt</a>,
data defining the location of the nonzero entries of the Wathen
matrix.
</li>
<li>
<a href = "wathen_ge_commands.txt">wathen_ge_commands.txt</a>,
gnuplot commands to display the data.
</li>
<li>
<a href = "wathen_ge.png">wathen_ge.png</a>,
an image of the sparsity pattern for the Wathen matrix.
</li>
<li>
<a href = "before_data.txt">before_data.txt</a>,
data defining the location of the nonzero entries of a matrix,
as created by DEAL.II.
</li>
<li>
<a href = "before_commands.txt">before_commands.txt</a>,
gnuplot commands to display the data.
</li>
<li>
<a href = "before.png">before.png</a>,
an image of the sparsity pattern for the before matrix.
</li>
<li>
<a href = "after_data.txt">after_data.txt</a>,
data defining the location of the nonzero entries of a matrix,
as created by DEAL.II (after reordering of variables).
</li>
<li>
<a href = "after_commands.txt">after_commands.txt</a>,
gnuplot commands to display the data.
</li>
<li>
<a href = "after.png">after.png</a>,
an image of the sparsity pattern for the after matrix.
</li>
<li>
<a href = "30x20_data.txt">30x20_data.txt</a>,
data defining the location of the nonzero entries of the 30x20
matrix.
</li>
<li>
<a href = "30x20_commands.txt">30x20_commands.txt</a>,
gnuplot commands to display the data.
</li>
<li>
<a href = "30x20.png">30x20.png</a>,
an image of the sparsity pattern for the 30x20 matrix.
</li>
</ul>
</p>
<h3 align = "center">
List of Routines:
</h3>
<p>
<ul>
<li>
<b>SPY_FILE</b> plots a sparsity pattern stored in a file.
</li>
<li>
<b>SPY_GE</b> plots a sparsity pattern for a general storage (GE) matrix.
</li>
<li>
<b>TIMESTAMP</b> prints the current YMDHMS date as a time stamp.
</li>
</ul>
</p>
<p>
You can go up one level to <a href = "../cpp_src.html">
the C++ source codes</a>.
</p>
<hr>
<i>
Last revised on 09 June 2014.
</i>
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