7.4.5. 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.

Required hardware/software:

None.

Building LAMMPS with the OPT package:

See the Build extras doc page for instructions.

Run with the OPT package from the command line:

lmp_mpi -sf opt -in in.script                # run in serial
mpirun -np 4 lmp_mpi -sf opt -in in.script   # run in parallel

Use the “-sf opt” command-line switch, 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 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

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.

7.4.5.1. Restrictions

None.