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:doc:`Return to Section accelerate overview <Section_accelerate>`
5.OPT package
-------------
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.
Here is a quick overview of how to use the OPT package. More details
follow.
.. parsed-literal::
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
.. parsed-literal::
lmp_mpi -sf opt -in in.script # run in serial
mpirun -np 4 lmp_mpi -sf opt -in in.script # run in parallel
**Required hardware/software:**
None.
**Building LAMMPS with the OPT package:**
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 :ref:`Section 2.4 <start_4>` of the manual. Type "Make.py -h" for
help.
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.
**Run with the OPT package from the command line:**
As in the lines above, use the "-sf opt" :ref:`command-line switch <start_7>`, which will automatically append
"opt" to styles that support it.
**Or run with the OPT package by editing an input script:**
Use the :doc:`suffix opt <suffix>` command, or you can explicitly add an
"opt" suffix to individual styles in your input script, e.g.
.. parsed-literal::
pair_style lj/cut/opt 2.5
**Speed-ups to expect:**
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.
**Guidelines for best performance:**
Just try out an OPT pair style to see how it performs.
Restrictions
""""""""""""
None.
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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