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<html>
<head>
<title>
NAS - A Revision of the NASA Kernel Benchmark Program
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
NAS <br> A Revision of the NASA Kernel Benchmark Program
</h1>
<hr>
<p>
<b>NAS</b>
is a C++ program which
is a revision of David Bailey's NASA kernel benchmark program.
</p>
<p>
The <b>NAS</b> benchmark program was developed around 1984, and
measured computational performance on a representative range
of realistic calculations. One motivation for this benchmark was
to move beyond the LINPACK benchmark, which focussed on a single
highly structured procedure.
</p>
<p>
Benchmarking computers has become much more difficult now that
memory, I/O, multicores and distributed memory have all become
significant factors in computing performance. Nonetheless, the
NAS benchmarks provide an interesting insight into the floating
point processing power of a system, and so, for this reason, a
version of the program has been created that retains the functionality
of the original, while being somewhat easier to transfer to
other languages.
</p>
<p>
One might expect comparable numerical performance of C++ and FORTRAN
programs. That this does not seem to happen for the C++ and FORTRAN90
versions of NAS reflects, most likely, the fact that the C++ version
was "translated" in a fairly straightforward manner, resulting in
some awkward and inefficient expressions; in particular, FORTRAN
arrays which were multiply-indexed were implemented in C++ as
vectors, with the resulting overhead of computing indices explicitly.
Thus, it is likely that a more careful revision of the C++ source
code would result in substantial performance improvements.
I, on the other hand, am simply terribly relieved that the C++ program
gets the right answers.
</p>
<h3 align = "center">
Usage:
</h3>
<p>
<blockquote>
<b>nas</b>
</blockquote>
runs the program, and prints the error, timing, and MegaFLOPS results.
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files described and 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>NAS</b> is available in
<a href = "../../c_src/nas/nas.html">a C version</a> and
<a href = "../../cpp_src/nas/nas.html">a C++ version</a> and
<a href = "../../f77_src/nas/nas.html">a FORTRAN77 version</a> and
<a href = "../../f_src/nas/nas.html">a FORTRAN90 version</a> and
<a href = "../../m_src/nas/nas.html">a MATLAB version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../cpp_src/linpack_bench/linpack_bench.html">
LINPACK_BENCH</a>,
a C++ program which
measures the time taken by <b>LINPACK</b> to solve a particular linear system.
</p>
<p>
<a href = "../../c_src/matmul/matmul.html">
MATMUL</a>,
a C program which
is an interactive matrix multiplication benchmark.
</p>
<p>
<a href = "../../f77_src/mdbnch/mdbnch.html">
MDBNCH</a>,
a FORTRAN77 program which
is a benchmark molecular simulation calculation.
</p>
<h3 align = "center">
Reference:
</h3>
<p>
<ol>
<li>
David Bailey, John Barton,<br>
The NAS Kernel Benchmark Program,<br>
Numerical Aerodynamics Simulations Systems Division,<br>
NASA Ames Research Center,<br>
13 June 1986.
</li>
</ol>
</p>
<h3 align = "center">
Source Code:
</h3>
<p>
<ul>
<li>
<a href = "nas.cpp">nas.cpp</a>, the source code.
</li>
<li>
<a href = "nas.sh">nas.sh</a>,
BASH commands to compile the source code.
</li>
</ul>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<ul>
<li>
<a href = "nas_output.txt">nas_output.txt</a>,
the output file.
</li>
</ul>
</p>
<h3 align = "center">
List of Routines:
</h3>
<p>
<ul>
<li>
<b>MAIN</b> is the main program for NAS.
</li>
<li>
<b>MXMTST</b> is the test program for MXM.
</li>
<li>
<b>MXM</b> computes the matrix product C = A * B.
</li>
<li>
<b>FFTTST</b> is the test program for CFFT2D1 and CFFTD2.
</li>
<li>
<b>CFFT2D1</b> performs complex radix 2 FFT''s on the first dimension.
</li>
<li>
<b>CFFT2D2</b> performs complex radix 2 FFT''s on the second dimension.
</li>
<li>
<b>CHOTST</b> is the test program for CHOLSKY.
</li>
<li>
<b>CHOLSKY</b> carries out Cholesky decomposition and back substitution.
</li>
<li>
<b>BTRTST</b> is the test program for BTRIX.
</li>
<li>
<b>BTRIX</b> is a block tridiagonal solver in one direction.
</li>
<li>
<b>GMTTST</b> is the test program for GMTRY.
</li>
<li>
<b>GMTRY</b> computes solid-related arrays.
</li>
<li>
<b>EMITST</b> is the test program for EMIT.
</li>
<li>
<b>EMIT</b> creates new vortices according to certain boundary conditions.
</li>
<li>
<b>VPETST</b> is the test program for VPENTA.
</li>
<li>
<b>VPENTA</b> inverts 3 pentadiagonal systems simultaneously.
</li>
<li>
<b>I4_MAX</b> returns the maximum of two I4's.
</li>
<li>
<b>I4_MIN</b> returns the smaller of two I4's.
</li>
<li>
<b>R8_ABS</b> returns the absolute value of an R8.
</li>
<li>
<b>R8_MAX</b> returns the maximum of two R8's.
</li>
<li>
<b>R8_MIN</b> returns the minimum of two R8's.
</li>
<li>
<b>R8VEC_COPY</b> copies an R8VEC.
</li>
<li>
<b>TIMESTAMP</b> prints the current YMDHMS date as a time stamp.
</li>
<li>
<b>WTIME</b> reports the elapsed wallclock time.
</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 11 November 2010.
</i>
<!-- John Burkardt -->
</body>
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</html>