Install and configure

First, ensure that you have a recent Python installed, since Fluidsim requires Python >= 3.9. Some issues regarding the installation of Python and Python packages are discussed in the main documentation of the project.

Installation methods without compilation

Install using pip without compilation


We strongly advice to install Fluidsim in a virtual environment. See the official guide Install packages in a virtual environment using pip and venv.

Fluidsim can be installed without compilation with pip:

pip install pip -U
pip install fluidsim

However, fluidsim requires fluidfft for pseudospectral solvers. Fluidsim and fluidfft can be both installed without compilation with the command:

pip install fluidsim[fft]

Moreover, fluidfft works with pluggins to compute FFTs with different methods (see the fluidfft documentation). For example, to install Fluidfft plugins using the FFTW library, one can run (but it will trigger compilation):

pip install fluidfft[fftw,fftwmpi,mpi_with_fftw]

Installing the conda-forge packages with conda or mamba

We recommend installing conda and mamba (using the conda-forge channel) with the miniforge installer.

If you just want to run sequential simulations and/or analyze the results of simulations, you can just install the fluidsim package:

mamba install fluidsim

For parallel simulations using MPI, let’s create a dedicated environment:

mamba create -n env_fluidsim ipython fluidsim "fluidfft[build=mpi*]" "h5py[build=mpi*]"

The environment can then be activated with conda activate env_fluidsim.

Optional dependencies

Fluidsim has 4 sets of optional dependencies, which can be installed with commands like pip install fluidsim[fft] or pip install fluidsim[fft, mpi]:

  • fft: mainly for pseudo spectral solvers using the Fourier basis.

  • mpi: for parallel computing using MPI. pip install fluidsim[mpi] installs mpi4py, which requires a local compilation.

  • test: for testing Fluidsim (can be done without the repository).

  • scipy

Environment variables and runtime configuration

Fluidsim is sensitive to environment variables:

  • FLUIDSIM_PATH: path where the simulation results are saved.

    In Unix systems, you can for example put this line in your ~/.bashrc:

    export FLUIDSIM_PATH=$HOME/data_fluidsim
  • FLUIDDYN_PATH_SCRATCH: working directory (can be useful on some clusters).

Dependencies with different flavours


Fluidsim uses Fluidfft to compute Fourier transforms. Have a look at the fluidfft documentation.

MPI simulations and mpi4py

Fluidsim can use mpi4py (which depends on a MPI implementation) for parallel simulations.


If the system has multiple MPI libraries, it is adviced to explicitly mention the MPI command. For instance to use Intel MPI:

CC=mpiicc pip install mpi4py --no-binary mpi4py

About h5py and HDF5_MPI

FluidSim is able to use h5py built with MPI support.


Prebuilt installations (for e.g. via h5py wheels) lacks MPI support. Most of the time, this is what you want. However, you can install h5py from source and link it to a hdf5 built with MPI support, as follows:

CC="mpicc" HDF5_MPI="ON" HDF5_DIR=/path/to/parallel-hdf5 pip install --no-deps --no-binary=h5py h5py
python -c 'import h5py; h5py.run_tests()'

In some cases you need to set C_INCLUDE_PATH variable before h5py installation. For example on Debian stretch:

export C_INCLUDE_PATH=/usr/include/openmpi/
CC="mpicc" HDF5_MPI="ON" HDF5_DIR=/path/to/parallel-hdf5 pip install --no-deps --no-binary=h5py h5py

See the h5py documentation for more details.