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lammps/doc/accelerate_opt.txt
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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.
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