# FAQ

## Applications: Can I use FluidSim for

:::{admonition} Wall bounded / multiphase / reactive flows ...?

Maybe. The built-in {mod}`solvers <fluidsim.solvers>` excels solving within
periodic domains with pseudospectral solvers. However, FluidSim is a framework,
and this allows FluidSim to interface with third-party solvers. See for
instance {mod}`fluidsim.base.basilisk`, {mod}`fluidsim.base.dedalus` and
[snek5000](https://snek5000.readthedocs.io).

:::

## Troubleshooting installation issues

Make sure you read the [installation guide](install) carefully.

:::{admonition} Permission denied while running `pip install fluidsim` from PyPI or `make develop` inside the repository.

This means you are probably using the Python bundled with the system and as a
user you are restricted from installing packages into it. If this is so, create
a [virtual environment].

:::

:::{admonition} *No module named pip* or `distutils.errors.DistutilsError`

Package manager `pip` was not installed into your environment or is too old. The
following commands should help:

```sh
python -m ensurepip
python -m pip install --upgrade pip
```

:::

:::{admonition} System freezes or becomes unresponsive as fluidsim starts to build extensions

By default `pythran` extensions try to use `gcc` and this is a
CPU and memory intensive compilation. Instead `pythran` can be configured to use
`clang`. See {ref}`pythranrc` for more details.

Additionally to reduce the load during installation one can [limit the number of
parallel processes used to build extensions](compile-args-j2).

:::

:::{admonition} `ModuleNotFoundError: No module named 'fluidsim_core. ...`

FluidSim depends on {mod}`fluidsim_core` and both follow the same versioning. Make
sure the versions match if you had used `pip install` or `conda install`. For
developers, `make develop` should install both as editable installations.

:::

[virtual environment]: https://packaging.python.org/guides/installing-using-pip-and-virtual-environments/#creating-a-virtual-environment