Installation

• GEANT4
  • Installation
  • CMake options
• Setting up eAST
  • Build and Install
  • HepMC3
  • Final steps
• Appendix
  • GEANT4 dependencies
    • Xerces
    • Qt
    • libxmu
    • Passing options to “make”
  • Running Geant4 graphics under WSL2

GEANT4

Installation

• eAST runs on top of the latest public version of Geant4, so before building eAST you need to install Geant4. The current Geant4 version is 11.1.0 – use this link to download and install.
• Please refer to the Geant4 installation guide and follow all instructions. In many cases (e.g. if the platform is Debian) Geant4 will need to be installed from source.
• The process involves using cmake, and it’s important that you use a proper build directory as recommended in the installation guide. Please see the CMake options section below for details on options.
• Before you commence the build please make sure that the compilers i.e. gcc and g++ are in the $PATH and their versions comply with GEANT requirements.
• cmake will produce helpful diagnostics if some dependencies are missing, in which case these will need to be installed (see the table and Appendix below). In case of this and other errors when using cmake the safest option is clean up the “build” directory and start the build procedure from scratch.
• During the build process certain files will be downloaded automatically from remote servers, so make sure your computer is online at that time.
• If the install path is in a folder to which the user doesn’t have write access (e.g. under “opt”), one may need to use root/chown or sudo to get necessary privileges.
• There is a post-installation step that should be followed to set the environment variables important for Geant4 operation.

CMake options

In order to successfuly build eAST it is mandatory that you set the options listed below when using cmake to build Geant4. As you can see from the table, if you start from scratch you may need to install the prerequisits first such as X11, Qt5, OpenGL and Xerces-C++ libraries. Please see the Appendix for comments and some practical advice about how to proceed.

A command line for cmake using these options might look like this:

cmake -DCMAKE_INSTALL_PREFIX=/install/path -DGEANT4_INSTALL_DATA=ON -DGEANT4_USE_OPENGL_X11=ON -DGEANT4_USE_GDML=ON -DGEANT4_USE_QT=ON /path/to/geant/directory

In certain cases (not very common) the user may need to build a version of Geant4 where multithreading is disabled. One such cases is creation of Python bindings on certain platforms. In such cases, the following option will need to be added:

-DGEANT4_BUILD_MULTITHREADED=OFF

Setting up eAST

Build and Install

• It is recommended that the user creates a build folder inside the main eAST directory; the example below assumes that this is the case
• During the build proccess, additional files may be downloaded, so internet access is required
• To customize the installation location, use the CMAKE_INSTALL_PREFIX option (see below)
• When building eAST cmake will attempt to find an existing HepMC3 installation in default locations
• A more reliable method is to specify the correct location with the HepMC3 option (see below)

The following is a working example of commands for the build and install procedure (assuming they are run from the eAST directory):

cmake -DCMAKE_INSTALL_PREFIX=/path/to/installdir -DHepMC3=~/path/to/HepMC3dir/ -S . -B build
cmake --build build
cmake --install build

The last command will copy libraries, binaries, data, and cmake configuration files into the predefined install location. If you elect to install into a system directory (e.g. under /opt etc) please see the notes in the Geant4 section above, regarding correct permissions. After installation has completed you probably want to ensure that (in this example) /path/to/installdir/bin is in the $PATH environment variable and /path/to/installdir/lib in $LD_LIBRARY_PATH.

HepMC3

Many use cases involve using the HepMC3 libraries so it is effectively a prerequisite for eAST. This is also implied in the build option illustrated in the previous section (cf. -DHepMC3). Please visit the HepMC3 page if you need to install HepMC3 from binaries or build it from source. When downloading the tar file as per instructions, it is possible that the link is stale, so the version number will need to be adjusted to point to an existing file.

Final steps

Once the HepMC3 installation is complete (or is already in place), in order for eAST to work, the environment variable LD_LIBRARY_PATH will need to be updated to include the path the the HepMC3 libraries. This can be done after sourcing the Geant4 post-installation script.

Appendix

GEANT4 dependencies

Xerces

The Xerces build and intallation webpage mentions cmake – although the latter is not explicitly invoked, and you only need to run configure and make. Read the web page carefully.

Qt

The Qt installation procedure has evolved over the years. Using the GUI installer provided by the developer appears to frequently cause problems. At the time of writing, this procedure is working:

# prerequisites:
sudo apt-get -y install build-essential openssl libssl-dev libssl1.0 libgl1-mesa-dev libqt5x11extras5
# qt:
sudo apt-get install qtbase5-dev
sudo apt-get install qtdeclarative5-dev

libxmu

sudo apt-get install -y libxmu-dev

Passing options to “make”

On many Linux platforms, cmake is relying on make for the build step. It is possible in these cases to pass helpful options (such as use multiple cores for compilation) to make by setting an environment variable:

export MAKEFLAGS=-j4

Running Geant4 graphics under WSL2

In some cases an extra step is needed to get the graphics driver to work correctly, for example in WSL2 the following setting is helpful:

export LIBGL_ALWAYS_INDIRECT=