Installing OPI

OPI provides a Python library for accessing ORCA and processing its results. Currently, it is distributed via PyPI and GitHub.

OPI can either be installed directly from PyPI:

pip install orca-pi

or from GitHub:

git clone https://github.com/faccts/opi.git
cd opi
python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install .

In order to use OPI properly we recommend to install it in a venv environment.

ORCA and Open MPI

OPI requires for most of its functionality that ORCA is installed on the host machine. ORCA has to be obtained separately from our download portal (commercial and academic) or from the ORCA Forum (academic). For parallel calculations also Open MPI is required. For most modern operating system Open MPI can usually be installed directly with the systems package manager. Otherwise, a suitable version has be obtained and compiled from their website.

Note that OPI is first introduced with ORCA 6.1 and is not compatible with earlier versions. The minimal supported ORCA version is always stored in ORCA_MINIMAL_VERSION

Config File

ORCA and Open MPI can be either be passed to OPI via the system path ($PATH and $LD_LIBRARY_PATH) or via a config file. The config file should be located at $XDG_CONFIG_HOME/opi/config.toml (usually $XDG_CONFIG_HOME points to $HOME/.config).

The config.toml file should contain the absolute path to the ORCA and Open MPI base folders. Where base folders mean the parent folder that contains the respective bin/ and lib/ folders.

ORCA_PATH = "/path/to/orca/"
# > Path to Open MPI installed with `apt`
MPI_PATH = "/usr"