.. _faq:

===========================
Frequently Asked Questions
===========================


.. _kim_fails:

I am using a KIM model, but it fails. What should I do?
=======================================================
- Check you have the model installed. You can use ``$ kim-api-collections-management list``
  to see what KIM models are installed.
- Check ``kim.log`` to see what the error is. Note that ``kim.log`` stores all the log
  info chronologically, so you may want to delete it and run you fitting code to get a
  fresh one.
- Make sure that parameters like ``cutoff``, ``rhocutoff`` is not used as fitting
  parameters. See :ref:`simulator_neighbor_error` for more.


.. _simulator_neighbor_error:

What does "error * * Simulator supplied GetNeighborList() routine returned error" in ``kim.log`` mean?
======================================================================================================
Probably you use parameters related to cutoff distance (e.g. ``cutoff`` and ``rhocutoff``)
as fitting parameters.  KLIFF build neighbor list only once at the beginning, and reuse it
during the optimization process. If the cutoff changes, the neighbor list could be invalid
any more.  Typically, in the training of potentials, we treat cutoffs as predefined
hyperparameters and do not optimize them. So simply remove them from your fitting
parameters.


I am using ``mpirun`` (``mpiexec``), but why the output shows it is `Running in multiprocessing mode with x processes`?
=======================================================================================================================
If you are running something like ``mpiexec -np 2 python example_kim_SW_Si.py`` and see
each minimization step executed twice, you may forget to install ``mpi4py``.
See :ref:`run_in_parallel` for more one how to run in parallel.