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<CENTER><A HREF = "Section_packages.html">Previous Section</A> - <A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> -
<A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
</CENTER>
<HR>
<P><A HREF = "Section_accelerate.html">Return to Section accelerate overview</A>
</P>
<H4>5.3.6 OPT package
</H4>
<P>The OPT package was developed by James Fischer (High Performance
Technologies), David Richie, and Vincent Natoli (Stone Ridge
Technologies). It contains a handful of pair styles whose compute()
methods were rewritten in C++ templated form to reduce the overhead
due to if tests and other conditional code.
</P>
<P>Here is a quick overview of how to use the OPT package. More details
follow.
</P>
<PRE>make yes-opt
make mpi # build with the OPT pacakge
Make.py -v -p opt -o mpi -a file mpi # or one-line build via Make.py
</PRE>
<PRE>lmp_mpi -sf opt -in in.script # run in serial
mpirun -np 4 lmp_mpi -sf opt -in in.script # run in parallel
</PRE>
<P><B>Required hardware/software:</B>
</P>
<P>None.
</P>
<P><B>Building LAMMPS with the OPT package:</B>
</P>
<P>The lines above illustrate how to build LAMMPS with the OPT package in
two steps, using the "make" command. Or how to do it with one command
via the src/Make.py script, described in <A HREF = "Section_start.html#start_4">Section
2.4</A> of the manual. Type "Make.py -h" for
help.
</P>
<P>Note that if you use an Intel compiler to build with the OPT package,
the CCFLAGS setting in your Makefile.machine must include "-restrict".
The Make.py command will add this automatically.
</P>
<P><B>Run with the OPT package from the command line:</B>
</P>
<P>As in the lines above, use the "-sf opt" <A HREF = "Section_start.html#start_7">command-line
switch</A>, which will automatically append
"opt" to styles that support it.
</P>
<P><B>Or run with the OPT package by editing an input script:</B>
</P>
<P>Use the <A HREF = "suffix.html">suffix opt</A> command, or you can explicitly add an
"opt" suffix to individual styles in your input script, e.g.
</P>
<PRE>pair_style lj/cut/opt 2.5
</PRE>
<P><B>Speed-ups to expect:</B>
</P>
<P>You should see a reduction in the "Pair time" value printed at the end
of a run. On most machines for reasonable problem sizes, it will be a
5 to 20% savings.
</P>
<P><B>Guidelines for best performance:</B>
</P>
<P>Just try out an OPT pair style to see how it performs.
</P>
<P><B>Restrictions:</B>
</P>
<P>None.
</P>
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