Using the SLAC Installation of the Geant4 Toolkit

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Current Installation

The latest Geant4 libraries are centrally maintained and installed so that users may build and link their applications to them, rather than build and maintain their own libraries.
Geant4 9.4 is now installed on the 32-bit and 64-bit Linux machines:

rhel4-32
rhel5-32
rhel4-64
rhel5-64

Access to older libraries, including Geant4 9.3 (patch02) is available upon request.
Various data files required for optional Geant4 processes and models are also centrally maintained and automatically accessed by the setup scripts.

Accessing the SLAC installation

To compile and link a simulation executable using the current Geant4 toolkit, several environment variables must first be set. This is done in a script which also chooses the combination of Geant4 and CLHEP libraries appropriate to the computing platform. The script can be found in

/afs/slac/package/geant4/g4setup.env

To begin:

choose a work directory, and in it,
mkdir geant4
cd geant4
cp /afs/slac/package/geant4/g4setup.env .
source g4setup.env

The essential variables set by this file are:

G4WORKDIR - working directory which will contain your specific code and the binary application
G4INSTALL - location of the installed code and libraries
G4SYSTEM - G4 code for the system architecture
CLHEP_BASE_DIR - base directory of the CLHEP libraries against which the toolkitis linked and against which your code should be linked
CLHEP_LIB - location in the SLAC directory structure of CLHEP libraries built for a given platform

g4setup.env must be sourced each time you log in and want to rebuild or run the executable. If you log in to a generic machine (e.g. noric) as opposed to a specific one (e.g. noric10), the machine, and hence the libraries may be different. In this case, clean and rebuild your application.

Alternate method: if you know the specific platform you are using (rhel4-32, for example):

mkdir geant4
cd geant4
cp /afs/slac/package/geant4/9.4/env-rhel4-32.csh .
source env-rhel4-32.csh (repeat this line each time you log in to this platform)
.sh versions of this script are also available

Visualization

Interfaces for several visualization drivers have been compiled into the toolkit libraries. Currently the setup scripts choose OPENGL, but the user may choose another driver by setting the appropriate environment variable before building the executable.

Building and Running the Executable

The following steps will lead you to a working executable with visualization using OPENGL:

go to your work directory (in the above example, geant4)
from the Geant4 installation copy the code for example 3:
- cp -r $G4INSTALL/examples/novice/N03 N03
cd to N03
gmake
- gmake will create tmp and bin directories in your work directory. The executable, named exampleN03, will be in /bin/$G4SYSTEM/
while in directory N03, run the executable:
- ../bin/$G4SYSTEM/exampleN03
if everything goes according to plan, you should see the Idle> prompt on your screen (after some preliminary output). From this prompt type
- /run/beamOn 1
to see an event displayed. Repeat until you get tired or bored.
when finished type
- exit
at the Idle> prompt.

At this point you are ready to add to and modify the code in your copy of N03. For more information about developing your own simulation code using Geant4, see the Application Developer's Guide .

Dennis Wright