Lampshade

Lampshade is a configuration-driven Python wrapper around LAMMPS for more convenient batch submission of simulation jobs.

The Python wrapper makes it possible to define (a list of) simulation parameters in a settings.ini file and run simulations for all (combinations of) parameters in a standard way, in a serial or parallel manner, as defined in settings.ini.

The name is a play on "LAMMPS": it sits around LAMMPS like a lampshade around a lamp.

Motivation

Lampshade was developed with the idea that the LAMMPS input file for a system should not be modified for running the system with different parameters. Instead, these parameters can be fed to LAMMPS using variables. However, the list of variables often grows long, and feeding them as CLI arguments becomes tiresome. Moreover, oftentimes one wants to run a 'parameter sweep' consisting of a range of simulations with different (combinations) of some of these parameters.

Lampshade streamlines this by:

• Allowing the user to configure these parameters in a settings.ini file
• Handling creating of subdirectories for each simulation, containing all relevant info
• Spawning a simulation for every combination of parameters in a sweep

Using Lampshade, a large parameter sweep can be started using just one command, with the wrapper handling submission of SLURM jobs and subdirectory creation, keeping a clean and organised directory structure.

Installation

Simply clone the repository using Git:

foo@bar:~$ git clone https://github.com/Compizfox/Lampshade.git

or download a release and extract it. The Git approach has the advantage that updating is as easy as git pull.

Dependencies

Lampshade requires at least Python 3.6. No further setup is needed (apart from the usual LAMMPS setup, obviously); Lampshade does not depend on any Python libraries outside the Standard Library.

Usage

Placing input file(s)

Place the input file(s) which describe your simulation in the root directory (that is, the same directory the Python files reside in). For example, your directory tree should read:

Lampshade
├── Job.py
├── README.md
├── run_simulation.py
├── run_slurm.py
├── settings.ini.example
├── Simulation.py
└── my_simulation.in

Creating a subdirectory for a job

The wrapper assumes that you create a subdirectory for every "job" (set of simulations corresponding to e.g. a parameter sweep). Let's create one now:

foo@bar:~/Lampshade$ mkdir my_job

In this job directory, the wrapper expects two files: the initial data file and settings.ini. The name of the initial data file is specified in settings.ini. Let's copy the included settings.ini.example to the subdirectory we just created:

foo@bar:~/Lampshade$ cd my_job
foo@bar:~/Lampshade/my_job$ cp ../settings.ini.example settings.ini

settings.ini

Now, it's up to you to set the correct values in settings.ini depending on what you want to do. Here is a quick rundown of the various variables:

• jobscript_header_file: Path to a file containing the jobscript header. In its most basic form, this contains just a hashbang line, but on HPC systems where a module system is used, you also want to add required modules here. If this is unset, it will load the default jobscript header file included with Lampshade (jobscript_header.sh).

• LAMMPS_path: Path to the LAMMPS executable, which is simply lmp on most systems. Change this if LAMMPS is installed under a different name/location on your system.

• LAMMPS_arguments: Arguments to always pass to LAMMPS. Defaults to -sf omp to use the OMP versions of styles for free speed-up.

• MPI_path: Path to the mpirun/srun executable.

• MPI_arguments Arguments to pass to the mpirun/srun executable. Empty by default.

• required_vars: Space-separated list of variables that need to be passed to LAMMPS. Reflects the variables used in the input file.

• slurm_sbatch_args: sbatch command for submitting jobs (SlurmJob specific). Append to this the appropriate sbatch options (such as -t xx:xx and -n x for the time limit and number of processors respectively).

• input_file: Name of the LAMMPS input file

• log_file: Name of the log file to write (inside the inner simulation directory)

[static_vars] contains LAMMPS variables and their values that are static within a job, i.e. the variables that do not change in a parameter sweep.

[dyn_vars] on the other hand contains the 'dynamic' variables: those that are varied within a parameter sweep. Values are specified space-separated, and a simulation is spawned for every combination of values.

Two variables have a special meaning: input_file and initial_data_file, because they represent names of files residing in directories above the working directory of the simulation. As such, these paths are rewritten automagically by the wrapper by prepending ../ where appropriate.

Running

To run a job, execute run_slurm.py from the root directory with the name of the job's subdirectory as argument:

foo@bar:~/Lampshade$ ./run_slurm.py my_job

The wrapper automatically creates subdirectories inside the job directory for every simulation. The output of the simulation is placed in these subdirectories. For example:

Lampshade
├── Job.py
├── README.md
├── run_simulation.py
├── run_slurm.py
├── settings.ini.example
├── Simulation.py
├── my_simulation.in
├── my_job
│   ├── settings.ini
│   ├── slurm-9126416.out
│   ├── data.gz
│   ├── grid_epp0.6000_eps0.2000
│   │   ├── log.lammps
│   │   └── ...
│   ├── grid_epp0.6000_eps0.4000
│   │   ├── log.lammps
│   │   └── ...
│   └── ...

Refer to the input for my Vapour Solvated Polymer Brush simulations for a complete example which uses Lampshade.

Developer documentation

Job defines an abstract class for a job (a range of simulations with some specified parameters), including the argument and setting parser. Simulations are spawned by calling the abstract method _spawn_simulations().

In the current version, the only simulation spawn engine is SlurmJob (run_slurm.py) which submits SLURM jobs, but it is possible to e.g. run simulations interactively in serial, or in parallel using multiprocessing, by extending Job and implementing _spawn_simulations() as appropriate.

SlurmJob generates an 'ephemeral' (not saved anywhere) SLURM jobscript and pipes it to sbatch (with options as defined by slurm_sbatch_args in settings.ini). The jobscript contains a call to run_simulation.py with various required JSON-serialized variables as arguments.

run_simulation.py (which runs on the compute node at runtime) then JSON-deserializes these variables from argv, instantiates a Simulation and calls run_gcmc() on it to start the simulation.

A Simulation creates a subdirectory and runs LAMMPS in a subprocess with the applicable variables.

Shown below is a diagram illustrating the execution flow:

License

This project is free software licensed under the GPL. See LICENSE for details.