2. Installation
2.1. Prerequisites
Generally, FLEXI requires the following packages:
git
CMake
Fortran and C/C++ compilers (GNU compilers recommended)
MPI libraries (OpenMPI recommended)
ParaView
LAPACK/OpenBLAS[1]
HDF5[1]
FFTW[1]
2.1.1. Installing the Dependencies from the Package Repositories
FLEXI has been tested on various Linux distributions, including Ubuntu and Debian, as well as OpenSUSE, CentOS and Fedora.
The required packages for DEB-based and RPM-based Linux distributions can be obtained from the apt and the dnf environment, respectively. Refer to Table 2.1 for the package names.
Package |
Debian / Ubuntu |
RHEL / Fedora |
|---|---|---|
Installation Command |
|
|
git |
|
|
CMake |
|
|
C/C++/Fortran |
|
|
MPI |
|
|
ZLIB |
|
|
ParaView |
|
|
LAPACK/OpenBLAS[1] |
|
|
HDF5[1] |
|
|
FFTW[1] |
|
|
Tip
On RPM-based distributions, you might need to load the MPI module using the command module load mpi.
2.1.2. Additional Configuration
On some systems it may be necessary to increase the size of the stack (part of the memory used to store information about active subroutines) in order to execute FLEXI correctly. This is done by entering the following command.
ulimit -s unlimited
2.2. Obtaining the Source Code
The FLEXI repository is available at GitHub. To obtain the most recent version you have three possibilities:
Clone the FLEXI repository from GitHub
git clone https://github.com/flexi-framework/flexi.git
Download FLEXI from GitHub:
wget https://github.com/flexi-framework/flexi/archive/master.tar.gz tar xzf master.tar.gz
Download a release FLEXI repository from GitHub
Attention
Cloning FLEXI from GitHub may not be possible on some HPC clusters due to restricted internet access. Please refer to the cluster’s user instructions for possible remedies, such as establishing a SOCKS proxy on a machine with unlimited internet access, as documented here for the HLRS at the University of Stuttgart.
2.3. Compiling the Code
In order to compile the code, change into the FLEXI root directory, create a new sub-folder, and use CMake to configure and compile the code
mkdir build
cmake -B build
cmake --build build
Custom configuration of compiler options may be done using
ccmake -B build
For a list of all compiler options see section Compiler Options.
The executables flexi and posti_visu (if enabled) are generated in the sub-directory build/bin/.
Note
In the remainder of this user guide, we omit the path to the FLEXI executable (and related tools), but assume assume it can be executed directly by typing flexi. This can be achieved by defining an alias or symbolic link, for example.
For Linux beginners, we provide a short explanation on how to achieve this usage behavior. In general, in order to execute a file, the command either has to be in the PATH environment variable or you have to enter the full path to it in the terminal. To enable typing only flexi, you can add a symbolic link to the FLEXI executable in the current directory, e.g., test case folder, by entering
ln -s [FLEXI_ROOT]/build/bin/flexi
Among the files in the current directory, this symbolic link will be listed as
flexi -> [FLEXI_ROOT]/build/bin/flexi
2.4. Running the Code
For a first minimal FLEXI simulation, navigate to the cavity tutorial folder and run FLEXI:
cd [FLEXI_ROOT]/tutorials/cavity/Basic_Re100
flexi parameter_flexi.ini
Convert the output files to the vtu format by entering
posti_visu cavity_State_0000000.200000000.h5
and visualize the generated files using, e.g., ParaView. Note that this conversion step requires enabling the posti_visu tool by toggling the POSTI flag in the CMake configuration (see section Compiling the Code above).