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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. More details
follow.
make yes-opt
make mpi # build with the OPT package
Make.py -v -p opt -o mpi -a file mpi # or one-line build via Make.py :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
[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 "Section
2.4"_Section_start.html#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" "command-line
switch"_Section_start.html#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 "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:]
Just try out an OPT pair style to see how it performs.
[Restrictions:]
None.
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