LAMMPS benchmark problems

This directory contains 5 benchmark problems which are discussed in the Benchmark section of the LAMMPS documentation.

Each of the 5 problems has 32,000 atoms and runs for 100 timesteps. Each can be run as a serial benchmark (on one processor) or in parallel. In parallel, each benchmark can be run as a fixed-size or scaled-size problem. For fixed-size benchmarking, the same 32K atom problem is run on various numbers of processors. For scaled-size benchmarking, the model size is increased with the number of processors. E.g. on 8 processors, a 256K-atom problem is run; on 1024 processors, a 32-million atom problem is run, etc.

A few sample log file outputs on different machines and different numbers of processors are included in this directory to compare your answers to. E.g. a log file like log.date.chain.lmp.scaled.foo.P is for a scaled-size version of the Chain benchmark, run on P processors of machine "foo" with the dated version of LAMMPS. Note that the Eam and Lj benchmarks may not give identical answers on different machines because of the "velocity loop geom" option that assigns velocities based on atom coordinates - see the discussion in the documentation for the velocity command for details.

The CPU time (in seconds) for the run is in the "Loop time" line of the log files, e.g.

Loop time of 3.89418 on 8 procs for 100 steps with 32000 atoms

Timing results for these problems run on various machines are listed on the Benchmarks page of the LAMMPS WWW Site.

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These are the 5 benchmark problems:

LJ = atomic fluid, Lennard-Jones potential with 2.5 sigma cutoff (55 neighbors per atom), NVE integration

Chain = bead-spring polymer melt of 100-mer chains, FENE bonds and LJ pairwise interactions with a 2^(1/6) sigma cutoff (5 neighbors per atom), NVE integration

EAM = metallic solid, Cu EAM potential with 4.95 Angstrom cutoff (45 neighbors per atom), NVE integration

Chute = granular chute flow, frictional history potential with 1.1 sigma cutoff (7 neighbors per atom), NVE integration

Rhodo = rhodopsin protein in solvated lipid bilayer, CHARMM force field with a 10 Angstrom LJ cutoff (440 neighbors per atom), particle-particle particle-mesh (PPPM) for long-range Coulombics, NPT integration

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Here is how to run each problem, assuming the LAMMPS executable is named lmp_foo, and you are using the mpirun command to launch parallel runs:

Serial (one processor runs):

lmp_foo < in.lj lmp_foo < in.chain lmp_foo < in.eam lmp_foo < in.chute lmp_foo < in.rhodo

Parallel fixed-size runs (on 8 procs in this case):

mpirun -np 8 lmp_foo < in.lj mpirun -np 8 lmp_foo < in.chain mpirun -np 8 lmp_foo < in.eam mpirun -np 8 lmp_foo < in.chute mpirun -np 8 lmp_foo < in.rhodo

Parallel scaled-size runs (on 16 procs in this case):

mpirun -np 16 lmp_foo -var x 2 -var y 2 -var z 4 < in.lj mpirun -np 16 lmp_foo -var x 2 -var y 2 -var z 4 < in.chain.scaled mpirun -np 16 lmp_foo -var x 2 -var y 2 -var z 4 < in.eam mpirun -np 16 lmp_foo -var x 4 -var y 4 < in.chute.scaled mpirun -np 16 lmp_foo -var x 2 -var y 2 -var z 4 < in.rhodo.scaled

For each of the scaled-size runs you must set 3 variables as -var command line switches. The variables x,y,z are used in the input scripts to scale up the problem size in each dimension. Imagine the P processors arrayed as a 3d grid, so that P = Px * Py * Pz. For P = 16, you might use Px = 2, Py = 2, Pz = 4. To scale up equally in all dimensions you roughly want Px = Py = Pz. Using the var switches, set x = Px, y = Py, and z = Pz.

For Chute runs, you must have Pz = 1. Therefore P = Px * Py and you only need to set variables x and y.