Installing Geant3

Geant3 with VMC requires the VMC core package and ROOT.

The vmc core package was separated from the ROOT source into a new stand-alone vmc package in the GitHub vmc-project organization. The motivation for this step was a gain in flexibility and faster workflow for new developments of multiple engine mode. The vmc package in ROOT is deprecated since ROOT version 6.18 (its compilation is optional) and it is going to be removed in the next ROOT version, 6.26. The VMC stand-alone is supported since Geant3 3.0.

Geant3 with VMC uses CMake to configure a build system for compiling and installing the headers, libraries and Cmake configuration files.

To install geant3:

  1. First get the Geant3 source from the Download page. We will assume that the Geant3 package sits in a subdirectory
/mypath/geant3
  1. Create build directory alongside our source directory
$ cd /mypath
$ mkdir geant3_build
$ ls
 geant3 geant3_build
  1. To configure the build, change into the build directory and run CMake:
$ cd /mypath/geant3_build 
$ cmake -DCMAKE_INSTALL_PREFIX=/mypath/geant3_install /mypath/geant3

  • If ROOT environment was defined using thisroot.{c}sh script, there is no need to provide the path to its installation. Otherwise, they can be provided using -DROOT_DIR cmake option.

  • Since Geant3 3.9, the VMC stand-alone library has to be provided using -DVMC_DIR cmake option. If the VMC stand-alone library is not found, the deprecated VMC library in ROOT (availble if ROOT was built with the vmc option enabled) can still be used, a deprecation warning will be issued in this case.

  • Since Geant3 4.0, the deprecated VMC library in ROOT cannot be used and building against ROOT built with the vmc option enabled will fail with CMake error.

  • The Geant3 library is built by default in RelWithDebInfo build mode (Optimized build with debugging symbols). This default can be changed via the standard CMake option CMAKE_BUILD_TYPE. The other useful values are

    • Release : Optimized build, no debugging symbols
    • Debug : Debugging symbols, no optimization
  1. After the configuration has run, CMake will have generated Unix Makefiles for building Geant3. To run the build, simply execute make in the build directory:
$ make -jN

where N is the number of parallel jobs you require (e.g. if your machine has a dual core processor, you could set N to 2).

  • If you need more output to help resolve issues or simply for information, run make as
$ make -jN VERBOSE=1
  1. Once the build has completed, you can install Geant3 to the directory you specified earlier in CMAKE_INSTALL_PREFIX by running
$ make install

The instructions above apply to the installation since the version 2.0. For the installation of the previous versions (1.x) see Installing geant3 - Older Versions