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5.3.6 OPT package :h4

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:

include the OPT package and build LAMMPS
use OPT pair styles in your input script :ul

The last step can be done using the "-sf opt" "command-line
switch"_Section_start.html#start_7.  Or the effect of the "-sf" switch
can be duplicated by adding a "suffix opt"_suffix.html command to your
input script.

[Required hardware/software:]

None.

[Building LAMMPS with the OPT package:]

Include the package and build LAMMPS:

To do this in one line, use the src/Make.py script, described in
"Section 2.4"_Section_start.html#start_4 of the manual.  Type "Make.py
-h" for help.  If run from the src directory, this command will create
src/lmp_opt using src/MAKE/Makefile.mpi as the starting
Makefile.machine:

Make.py -p opt -o opt file mpi :pre

Or you can follow these steps:

cd lammps/src
make yes-opt
make machine :pre

If you are using Intel compilers, then the CCFLAGS setting in
Makefile.machine needs to include "-restrict".

[Run with the OPT package from the command line:]

Use the "-sf opt" "command-line switch"_Section_start.html#start_7,
which will automatically append "opt" to styles that support it.

lmp_machine -sf opt -in in.script
mpirun -np 4 lmp_machine -sf opt -in in.script :pre

[Or run with the OPT package by editing an input script:]

Use the "suffix opt"_suffix.html command, or you can explicitly add an
"opt" suffix to individual styles in your input script, e.g.

pair_style lj/cut/opt 2.5 :pre

[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:]

None.  Just try out an OPT pair style to see how it performs.

[Restrictions:]

None.