A Python interface for ab initio path integral molecular dynamics simulations. i-PI is composed of a Python server (i-pi itself, that does not need to be compiled but only requires a relatively recent version of Python and Numpy) that propagates the (path integral) dynamics of the nuclei, and of an external code that acts as a client and computes the electronic energy and forces.
This is typically a patched version of an electronic structure code, but a simple self-contained Fortran driver that implements Lennard-Jones and Silvera-Goldman potentials is included for test purposes.
To use i-PI with already existing drivers, install and update using Pip:
$ pip install -U i-PI
Test with Pytest:
$ pip install pytest $ pytest --pyargs ipi.tests
To develop i-PI or test it with the self-contained driver, follow these instructions. It is assumed that i-PI will be run from a Linux environment, with a recent version of Python, Numpy and gfortran, and that the terminal is initially in the i-pi package directory (the directory containing this file), which you can obtain by cloning the repository:
$ git clone https://github.com/i-pi/i-pi.git
Source the environment settings file env.sh as $ source env.sh or $ .
env.sh. It is useful to put this in your .bashrc or other settings file if
you always want to have i-PI available.
$ cd drivers $ make $ cd ..
This will first start the wrapper in the background, redirecting the output to a log file, and then run a couple of instances of the driver code. The progress of the wrapper is followed by monitoring the log file with the tail Linux command.
Optionally, you can make a copy of the directory with the example somewhere else if you want to keep the i-PI directory clean.
$ cd examples/tutorial/tutorial-1/ $ i-pi tutorial-1.xml > log & $ i-pi-driver -h localhost -p 31415 -m sg -o 15 & $ i-pi-driver -h localhost -p 31415 -m sg -o 15 & $ tail -f log
The monitoring can be interrupted with CTRL+C when the run has finished (5000 steps).
The automatic test suite can be run by calling the i-pi-test script. You need to have the pytest package installed
$ i-pi-test
See more details in the README file inside the ipi_tests folder.
i-PI is an open source project, and everyone is welcome to contribute with bug fixes, documentation, examples, new features, regression tests, etc.
Your contribution should be based on the master branch. We kindly ask you to first fork the project, make your changes, make sure you comply with all items in our checklist below, and finally create a pull request (PR).
Checklist to create a pull request:
- The PR follows our format compliance (based on black and flake8 as explained above)
- All the new classes and functions include the corresponding docstrings
(If the PR adds a new functionally, please fulfill the next two requirements as well)
- Add a working example to the examples folder to showcase the new functionality
- Add a regression test to the i-pi/ipi_tests/regression_tests folder (see the corresponding README file for further details)
- Make sure that all the automatic checks pass without any error
We are looking forward to your contribution!
i-PI code should be compliant to a minimal subset of PEP-8 recommendations. Currently, we require the use of black as formatter and linter. We also ask for the usage of flake8 for syntactic checks, which is also part of linting. In most systems, both packages can be easily installed using pip. BEFORE proceeding to a pull request, the minimal requirement is that you run
$ make lint $ make pretty
This will ensure the formatting and linting requirement are applied in the whole directory tree. Please resolve any warnings or errors that may appear. Your commit will not pass the CI tests otherwise.
For a more flexible setup, we also provide the script i-pi-style, for which instructions can be obtained by typing
$ i-pi-style -h