Command Line Interface
A separate command line tool for OpenPathSamplng can be installed. It is
available via either
conda install -c conda-forge openpathsampling-cli # or pip install openpathsampling-cli
Once you install this, you’ll have access to the command
openpathsampling in your shell (although we recommend aliasing that to
ops – save yourself some typing!)
This command is a gateway to many subcommands, just like
pip (which have subcommands such as
git (which has
subcommands such as
commit). You can get a full listing all
the subcommands with
openpathsampling --help. For more information on
any given subcommand, use
openpathsampling SUBCOMMAND --help, replacing
SUBCOMMAND with the subcommand you’re interested in.
Here, we will provide a description of a few of the subcommands that the CLI tool provides. This documentation may not be fully up-to-date with the more recent releases of the CLI, so use the CLI help tools to get a fuller understanding of what is included.
For more details on how the CLI interprets its arguments, and to learn how to develop plugins for the CLI, see its documentation. The CLI subcommands are defined through a plugin system, which makes it very easy for developers to create new subcommands.
CLI documentation: https://openpathsampling-cli.readthedocs.io/
CLI code repository: https://github.com/openpathsampling/openpathsampling-cli/
Workflow with the CLI
As always, the process of running a simulation is (1) set up the simulation; (2) run the simulation; (3) analyze the simulation. The CLI is mainly focused on step 2, although it also has tools that generally help with OPS files.
To use it, you’ll want to first set up your simulation, e.g., in a Jupyter
notebook, and save the simulation objects to a storage file with
storage.save(obj). You should tag you initial conditions with, e.g.,
storage.tags['initial_conditions'] = init_conds.
Close that storage file when you’re ready to run the simulation, and then you can run it with, e.g.,
openpathsampling pathsampling setup.nc -o output.nc --nsteps 1000
If the file you created,
setup.nc has exactly one move scheme and has a
sample set tagged as
initial_conditions, the CLI will figure that out.
Your output will be in
output.nc, and you can analyze it in a Jupyter
notebook, just as before.
Note that this can be especially useful when computing remotely. You can set
up on your local machine, and then you just need to transfer the
setup.nc to the remote machine (assuming you use internally-stored
Finding your way around the CLI
Like many command line tools, the OPS CLI has the options
--help to get help. If you run
openpathsampling --help you should
see something like this
Usage: openpathsampling [OPTIONS] COMMAND [ARGS]... OpenPathSampling is a Python library for path sampling simulations. This command line tool facilitates common tasks when working with OpenPathSampling. To use it, use one of the subcommands below. For example, you can get more information about the pathsampling tool with: openpathsampling pathsampling --help Options: --log PATH logging configuration file -h, --help Show this message and exit. Simulation Commands: visit-all Run MD to generate initial trajectories equilibrate Run equilibration for path sampling pathsampling Run any path sampling simulation, including TIS variants Miscellaneous Commands: contents list named objects from an OPS .nc file append add objects from INPUT_FILE to another file
--log option takes a logging configuration file (e.g., logging.conf,
and sets that logging behavior. If you use it, it must come before the
You can find out more about each subcommand by putting
the subcommand name, e.g.,
openpathsampling pathsampling --help, which
Usage: openpathsampling pathsampling [OPTIONS] INPUT_FILE General path sampling, using setup in INPUT_FILE Options: -o, --output-file PATH output ncfile [required] -m, --scheme TEXT identifier for the move scheme -t, --init-conds TEXT identifier for initial conditions (sample set or trajectory) -n, --nsteps INTEGER number of Monte Carlo trials to run -h, --help Show this message and exit.
Here you see the list of the options for the running a path sampling simulation. In general, path sampling requires an output file, a move scheme and initial conditions from some input file, and the number of steps to run. Note that only the output file is technically required: the CLI will default to running 0 steps (essentially, testing the validity of your setup), and it can try to guess the move scheme and initial conditions. In general, the way it guesses follows the following path:
If there is only one object of the suitable type in the INPUT_FILE, use that.
If there are multiple objects of the correct type, but only one has a name, use the named object.
In special cases it looks for specific names, such as
initial_conditions, and will use those.
Full details on how various CLI parameters search the storage can be seen in the Parameter Interpretation section of the CLI docs.
One of the main concepts when working with the CLI is that you can create all the OPS simulation objects without running the simulation, save them in an OPS storage file, and then load them again to actually run your simulation. For simulation commands, the options all deal with loading simulation objects from storage.
Here are some of the simulation commands implemented in the OPS CLI:
visit-all: create initial trajectories by running MD until all states have been visited (works for MSTIS or any 2-state system); must provide states, engine, and initial snapshot on command line
equilibrate: run equilibration for path sampling (until first decorrelated trajectory); must provide move scheme and initial conditions on the command line
pathsampling: run path sampling with a given move scheme (suitable for custom TPS schemes as well as TIS/RETIS); must provide move scheme, iniital conditions, and number of MC steps on command line
Even for users who prefer to develop their OPS projects entirely in Python, foregoing the CLI tools to run simulations, some of the “miscellaneous” commands are likely to be quite useful. Here are some that are available in the CLI:
contents: list all the named objects in an OPS storage, organized by store (type); this is extremely useful to get the name of an object to use
append: add an object from once OPS storage into another one; this is useful for getting everything into a single file before running a simulation
Customizing the CLI
The OPS CLI uses a flexible plugin system to enable users to easily add custom functionality. This way, you can create and distribute custom plugins, giving more functionality to other users who would benefit from it, without adding everything to the core package and thus overwhelming new users.
Installing a plugin is easy: just create the directory
$HOME/.openpathsampling/cli-plugins/, and copy the plugin Python script
into there. For details on how to write a CLI plugin, see the CLI