.. _quickstart:

Quick start
===========

Install UPET with ``pip``:

.. code-block:: bash

   pip install upet

Then run a single-point energy and force evaluation on a bulk silicon cell
using the ASE-compatible :py:class:`~upet.calculator.UPETCalculator`:

.. code-block:: python

   from upet.calculator import UPETCalculator
   from ase.build import bulk

   atoms = bulk("Si", cubic=True, a=5.43, crystalstructure="diamond")
   calculator = UPETCalculator(model="pet-mad-s", version="1.5.0", device="cpu")
   atoms.calc = calculator

   energy = atoms.get_potential_energy()
   forces = atoms.get_forces()

The first call downloads the model checkpoint from the `HuggingFace
repository <https://huggingface.co/lab-cosmo/upet>`_ and caches it locally,
so subsequent calls are fast.

Next steps
----------

- See :ref:`installation` for the full list of installation methods (PyPI,
  GitHub, ``uv``, pinning a specific version).
- See :ref:`usage` for the complete feature surface: ASE workflows,
  batched evaluation with ``metatrain``, LAMMPS, i-PI, TorchSim, and
  GROMACS.
- See :ref:`models` for the list of available pre-trained models and
  their recommended use cases.