These are examples that work the MDI package in LAMMPS which uses the MolSSI MDI library for coupling codes together and communicating between them with MDI messages. In MDI lingo, one code is the driver and another code is the engine. The 2 codes can be written in any language; C++ (LAMMPS) and Python are illustrated here. The 2 codes can each be stand-alone codes, in which case they can be run on different numbers of processors. The 2 codes can communicate either via TCP (sockets) or via MPI. For the TCP case, the driver and engine need to be launched separately, e.g. in 2 windows on your desktop machine. For the MPI case, a single mpirun command launches both codes. Alternatively the engine code can be a plugin library which the driver code loads, in which case the driver and engine run on the same processors. LAMMPS supports operating in all these MDI modes. It can be an engine operating either as a stand-alone code or as a plugin. It can also be a driver and couple to an engine that is either a stand-alone code or a plugin. Examples for all these use cases are in this directory. The example commands below illustrate how to run all the variants. To use LAMMPS as a plugin engine, you must build it as a shared library. Something like this, which also builds the normal LAMMPS executable lmp_mpi: cd src make yes-mdi make mode=shlib mpi To use the serial_driver.py example you will need Python 3 with Numpy and mpi4py available in your Python. Make sure LAMMPS and Python are using same the same version of MPI. ------------------------------------------------- ------------------------------------------------- * Example #1 = run ab inito MD (AIMD) Two instances of LAMMPS operate as a driver and engine As an engine, LAMMPS is a surrogate for a quantum code Note that the 2 input scripts in.aimd.alone and in.aimd.driver have an option for running in NVE vs NPT mode. Comment in/out the appropriate line to change modes. Nothing needs to be changed in the in.aimd.engine or in.aimd.engine.plugin scripts. --- Run the entire calculation with a single instance of LAMMPS by itself results should be identical to running this example with MDI % lmp_mpi < in.aimd.alone With MDI, the thermo output of the driver should match the thermo output of the in.aimd.alone script. --- Run with TCP: 1 proc each % lmp_mpi -mdi "-name aimd -role DRIVER -method TCP -port 8021" -log log.aimd.driver -in in.aimd.driver % lmp_mpi -mdi "-name LAMMPS -role ENGINE -method TCP -port 8021 -hostname localhost" -log log.aimd.engine -in in.aimd.engine --- Run with TCP: 3 procs + 4 procs % mpirun -np 3 lmp_mpi -mdi "-name aimd -role DRIVER -method TCP -port 8021" -log log.aimd.driver -in in.aimd.driver % mpirun -np 4 lmp_mpi -mdi "-name LAMMPS -role ENGINE -method TCP -port 8021 -hostname localhost" -log log.aimd.engine -in in.aimd.engine --- Run with MPI: 1 proc each % mpirun -np 1 lmp_mpi -mdi "-name aimd -role DRIVER -method MPI" -log log.aimd.driver -in in.aimd.driver : -np 1 lmp_mpi -mdi "-name LAMMPS -role ENGINE -method MPI" -log log.aimd.engine -in in.aimd.engine --- Run with MPI: 3 procs + 4 procs % mpirun -np 3 lmp_mpi -mdi "-name aimd -role DRIVER -method MPI" -log log.aimd.driver -in in.aimd.driver : -np 4 lmp_mpi -mdi "-name LAMMPS -role ENGINE -method MPI" -log log.aimd.engine -in in.aimd.engine --- Run in plugin mode: 1 proc % lmp_mpi -mdi "-name aimd -role DRIVER -method LINK -plugin_path /home/sjplimp/lammps/git/src" -log log.aimd.driver.plugin -in in.aimd.driver.plugin --- Run in plugin mode: 3 procs % mpirun -np 3 lmp_mpi -mdi "-name aimd -role DRIVER -method LINK -plugin_path /home/sjplimp/lammps/git/src" -log log.aimd.driver.plugin -in in.aimd.driver.plugin ------------------------------------------------- ------------------------------------------------- * Example #2 = Python driver runs a sequence of unrelated LAMMPS calculations Each calculation can be a single-point evaluation, MD run, or minimization The sequence_driver.py code allows for optional switches in addition to -mdi (required) and the -plugin and -plugin_args switches which are used to link to an engine as a plugin library. The example run commands below just use the default values of the optional switches. The switches are also explained at the top of the file; the info is copied here: # -n 3 # number of calculations to perform, default = 3 # -mode eval/run/min # style of calculations: single snapshot evals, dynamics, minimization # default = run # -size Nx Ny Nz # cubic lattice, default = 2 2 2 # -rho 0.75 0.1 # reduced density and random variation thereof, default = 0.75 0.1 # -delta 0.1 # randomly perturb atoms initially by this distance, default 0.1 # -nsteps 100 # number of timesteps in dynamics runs, default = 100 # -temp 1.0 # initial temperature in dynamics runs, default = 1.0 # -tol 0.001 # tolerance for minimizations, default = 0.001 # -seed 12345 # random number seed > 0, default = 12345 --- Run with TCP: 1 proc each % python3 sequence_driver.py -mdi "-role DRIVER -name sequence -method TCP -port 8021" % lmp_mpi -mdi "-role ENGINE -name LAMMPS -method TCP -port 8021 -hostname localhost" -log log.sequence -in in.sequence --- Run with TCP: 2 proc + 4 procs % mpirun -np 2 python3 sequence_driver.py -mdi "-role DRIVER -name sequence -method TCP -port 8021" % mpirun -np 4 lmp_mpi -mdi "-role ENGINE -name LAMMPS -method TCP -port 8021 -hostname localhost" -log log.sequence -in in.sequence --- Run with MPI: 1 proc each % mpirun -np 1 python3 sequence_driver.py -mdi "-role DRIVER -name sequence -method MPI" : -np 1 lmp_mpi -mdi "-role ENGINE -name LAMMPS -method MPI" -log log.sequence -in in.sequence --- Run with MPI: 2 procs + 4 procs % mpirun -np 2 python3 sequence_driver.py -mdi "-role DRIVER -name sequence -method MPI" : -np 4 lmp_mpi -mdi "-role ENGINE -name LAMMPS -method MPI" -log log.sequence -in in.sequence --- Run in plugin mode: 1 proc % python3 sequence_driver.py -plugin lammps -mdi "-role DRIVER -name sequence -method LINK -plugin_path /home/sjplimp/lammps/git/src" -plugin_args "-log log.sequence -in in.sequence" --- Run in plugin mode: 3 procs % mpirun -np 3 python3 sequence_driver.py -plugin lammps -mdi "-role DRIVER -name sequence -method LINK -plugin_path /home/sjplimp/lammps/git/src" -plugin_args "-log log.sequence -in in.sequence" ------------------------------------------------- ------------------------------------------------- * Example #3 = run AIMD with Python driver code and 2 LAMMPS instances as engines First LAMMPS instance performs the MD timestepping Second LAMMPS instance is surrogate QM = computes forces The aimd_driver.py code allows for an optional switch in addition to -mdi (required) and the -plugin and -plugin_args swiches which are used to link to the 2 engines as a plugin libraries. The example run commands below use the default values of the optional switch. The switch is also explained the top of the file; the info is copied here: # -nsteps 5 # number of timesteps in dynamics runs, default = 5 --- Run the entire calculation with a single instance of LAMMPS by itself results should be identical to running this example with MDI % lmp_mpi < in.aimd.alone With MDI, the driver prints the QM and Total energies. These should match the PotEng and TotEng output of the in.aimd.alone script. --- Run with TCP: 1 proc each % python3 aimd_driver.py -mdi "-role DRIVER -name aimd -method TCP -port 8021" % lmp_mpi -mdi "-role ENGINE -name MM -method TCP -port 8021 -hostname localhost" -log log.aimd.mm -in in.aimd.mm % lmp_mpi -mdi "-role ENGINE -name QM -method TCP -port 8021 -hostname localhost" -log log.aimd.qm -in in.aimd.qm --- Run with TCP: 2 procs + 2 procs + 3 procs % mpirun -np 2 python3 aimd_driver.py -mdi "-role DRIVER -name aimd -method TCP -port 8021" % mpirun -np 2 lmp_mpi -mdi "-role ENGINE -name MM -method TCP -port 8021 -hostname localhost" -log log.aimd.mm -in in.aimd.mm % mpirun -np 3 lmp_mpi -mdi "-role ENGINE -name QM -method TCP -port 8021 -hostname localhost" -log log.aimd.qm -in in.aimd.qm --- Run with MPI: 1 proc each % mpirun -np 1 python3 aimd_driver.py -mdi "-role DRIVER -name aimd -method MPI" : -np 1 lmp_mpi -mdi "-role ENGINE -name MM -method MPI" -log log.aimd.mm -in in.aimd.mm : -np 1 lmp_mpi -mdi "-role ENGINE -name QM -method MPI" -log log.aimd.qm -in in.aimd.qm --- Run with MPI: 2 procs + 2 procs + 3 procs % mpirun -np 2 python3 aimd_driver.py -mdi "-role DRIVER -name aimd -method MPI" : -np 2 lmp_mpi -mdi "-role ENGINE -name MM -method MPI" -log log.aimd.mm -in in.aimd.mm : -np 3 lmp_mpi -mdi "-role ENGINE -name QM -method MPI" -log log.aimd.qm -in in.aimd.qm