2.8. How to Set Up an Interactive Session

2.8. How to Set Up an Interactive Session
	Chapter 2. Getting Started with Geant4 - Running a Simple Example

2.8.1. Introduction

2.8.1.1. Roles of the "intercoms" category

The "intercoms" category provides an expandable command interpreter. It is the key mechanism of Geant4 to realize secure user interactions in all categories without being annoyed by the dependencies among categories. The Geant4 commands can be used both in a interactive terminal session and in a batch mode with a maco file or a direct C++ call.

2.8.1.2. User Interfaces to steer the simulation

Geant4 can be controllled by a seriese of Geant4 UI commands. The "intercoms" category provides the abstract class G4UIsession that processes interactive commands. The concrete implementation of (graphical) user interfaceis is located in the "interfaces" category. This interfacing strategy opens an important door towards various user interface tools, and allows Geant4 to utilize the state-of-the-art GUI tools such as Motif, Qt, and Java etc. The richness of the collaboration realizes various user interfaces to the Geant4 command system. The following interfaces is currently available;

Character terminal (dumb terminal and tcsh-like terminal), that is the default user interface of Geant4
Xm, Win32, Qt variations of the above terminal by using a Motif, Qt or Windows widget
GAG, a fully graphical user interface and its network extension GainServer of the client/server type.

Implementation of the user sesssions (1 and 2) is included in the source/interfaces/basic directory. As for GAG, the front-end class is included in the source/interfaces/GAG directory, while its partner GUI package MOMO.jar is available under the environments/MOMO directory. MOMO.jar, Java archive file, contains not only GAG, but also GGE and other helper packages. Supplementary information is available from the author's web page (see URL below).

GAG, GainServer's client GUI Gain: http://www-geant4.kek.jp/~yoshidah

2.8.2. A Short Description of Available Interface Classes

2.8.2.1. G4UIterminal and G4UItcsh classes

These interfaces open a session on the character terminal. G4UIterminal runs on all platforms supported by Geant4, including cygwin on Windows. The following built-in commands are available in G4UIterminal;

cd, pwd: change, display the current command directory.
ls, lc: list commands and subdirectories in the current directory.
history: show previous commands.
!historyID: reissue previous command.
?command: show current parameter values of the command.
help command: show command help.
exit: terminate the session.

G4UItcsh supports user-friendly key bindings a-la-tcsh. G4UItcsh runs on Solaris and Linux. The following keybindings are supported;

^A: move cursor to the top
^B: backward cursor ([LEFT] cursor)
^C (except Windows terminal): abort a run (soft abort) during event processing. A program will be terminated while accepting a user command.
^D: delete/exit/show matched list
^E: move cursor to the end
^F: forward cursor ([RIGHT] cursor)
^K: clear after the cursor
^N: next command ([DOWN] cursor)
^P: previous command ([UP] cursor)
TAB: command completion
DEL: backspace
BS: backspace

The example below shows how to set a user's prompt.

  G4UItcsh* tcsh = new G4UItcsh();
  tcsh-> SetPrompt("%s>");

The following strings are supported as substitutions in a prompt string.

%s: current application status
%/: current working directory
%h: history number

Command history in a user's session is saved in a file $(HOME)/.g4_hist that is automatically read at the next session, so that command history is available across sessions.

2.8.2.2. G4UIXm, G4UIQt and G4UIWin32 classes

These interfaces are versions of G4UIterminal implemented over libraries Motif, Qt and WIN32 respectively. G4UIXm uses the Motif XmCommand widget, G4UIQt the Qt dialog widget, and G4UIWin32 the Windows "edit" component to do the command capturing. These interfaces are useful if working in conjunction with visualization drivers that use the Xt library, Qt library or the WIN32 one.

A command box is at disposal for entering or recalling Geant4 commands. Command completion by typing "TAB" key is available in the command box. The shell commands "exit, cont, help, ls, cd..." are also supported. A menu bar can be customized through the AddMenu and AddButton method. Ex:

/gui/addMenu: test Test
/gui/addButton: test Init /run/initialize
/gui/addButton: test "Set gun" "/control/execute gun.g4m"
/gui/addButton: test "Run one event" "/run/beamOn 1"

G4UIXm runs on Unix/Linux with Motif. G4UIQt run everywhere with Qt. G4UIWin32 runs on Windows.

2.8.2.3. G4UIGAG and G4UIGainServer classes

They are the front-end classes of Geant4 which make connection with their respective graphical user interfaces, GAG (Geant4 Adaptive GUI) via pipe, and Gain (Geant4 adaptive interface for network) via sockets. While GAG must run on the same system (Windows or Unixen) as a Geant4 application, Gain can run on a remote system (Windows, Linux, etc.) in which JRE (Java Runtime Environment) is installed. A Geant4 application is invoked on a Unix (Linux) system and behaves as a network server. It opens a port, waiting the connection from the Gain. Gain is capable to connect to multiple Geant4 "servers" on Unixen systems at different institutes.

Client GUIs, GAG and Gain have almost similar look-and-feel. So, GAG's functionalities are briefly explained here. Please refer to the URL previously mentioned for details.

Using GAG, user can select a command, set its parameters and execute it. It is adaptive, in the sense that it reflects the internal states of Geant4 that is a state machine. So, GAG always provides users with the Geant4 commands which may be added, deleted, enabled or disabled during a session. GAG does nothing by itself but to play an intermediate between user and an executable simulation program via pipes. Geant4's front-end class G4UIGAG must be instantiated to communicate with GAG. GAG runs on Linux and Windows. MOMO.jar can be run by a command;

   %java -jar  $G4INSTALL/environments/MOMO/MOMO.jar

GAG has following functions.

GAG Menu:: The menus are to choose and run a Geant4 executable file, to kill or exit a Geant4 process and to exit GAG. Upon the normal exit or an unexpected death of the Geant4 process, GAG window are automatically reset to run another Geant4 executable.
Geant4 Command tree:: Upon the establishment of the pipe connection with the Geant4 process, GAG displays the command menu, using expandable tree browser whose look and feel is similar to a file browser. Disabled commands are shown in opaque. GAG doesn't display commands that are just below the root of the command hierarchy. Direct type-in field is available for such input. Guidance of command categories and commands are displayed upon focusing. GAG has a command history function. User can re-execute a command with old parameters, edit the history, or save the history to create a macro file.
Command Parameter panel:: GAG's parameter panel is the user-friendliest part. It displays parameter name, its guidance, its type(s) (integer, double, Boolean or string), omittable, default value(s), expression(s) of its range and candidate list(s) (for example, of units). Range check is done by intercoms and the error message from it is shown in the pop-up dialog box. When a parameter component has a candidate list, a list box is automatically displayed . When a file is requested by a command, the file chooser is available.
Logging:: Log can be redirected to the terminal (xterm or cygwin window) from which GAG is invoked. It can be interrupted as will, in the middle of a long session of execution. Log can be saved to a file independent of the above redirection . GAG displays warning or error messages from Geant4 in a pop-up warning widget.

2.8.3. Building the Interface Libraries

The libraries that do not depend on external packages are created by default, using Geant4 configure scripts. They include G4UIterminal, G4UItcsh and G4UIGAG in libraries libG4UIbasic.a/so and libG4UIGAG.a/so. G4UIGainServer.o is packed in the libG4UIGAG.

To make the libraries of G4UIXm and G4UIWin32 , respective environment variables G4UI_BUILD_XM_SESSION, G4UI_BUILD_QT_SESSION and G4UI_BUILD_WIN32_SESSION must be set explicitly before creating libraries.

If the environment variable G4UI_NONE is set, no interface libraries are built at all.

The scheme of building the user interface libraries is specified in "$G4INSTALL/config/G4UI_BUILD.gmk" makefile and the dependencies on the external packages are specified in "$G4INSTALL/config/interactivity.gmk".

2.8.4. How to Use the Interface in Your Application

To use a given interface (G4UIxxx where xxx = terminal,Xm, Win32, Qt, GAG, GainServer) in your program, there are two ways.

Calling G4UIxxx directly :

   #include "G4Uixxx.hh"
// to instantiate a session of your choice and start the session
   G4UIsession* session = new G4UIxxx;
   session->SessionStart();
// the line next to the "SessionStart" is necessary to finish the session
   delete session;

If you want to select a session type according to your environment variable, the code can be:

// to include the class definition in the main program:
   #if defined(G4UI_USE_TCSH)
     #include "G4UIterminal.hh"
     #include "G4UItcsh.hh"
   #elif defined(G4UI_USE_XM)
     #include "G4UIXm.hh"
   ....
   #endif

   #if defined(G4UI_USE_TCSH)
     session = new G4UITerminal(new G4UItcsh);
   #elif defined(G4UI_USE_XM)
     session = new G4UIXm(argc,argv);
   #elif ...

Note : For a tcsh session, the second line must be

      G4UIsession* session = new G4UIterminal(new G4UItcsh);

If the user wants to deactivate the default signal handler (soft abort) raised by "Ctr-C", the false flag can be set in the second argument of the G4UIterminal constructor like;

   G4UIsession* session = new G4UIterminal(new G4UItcsh, false).

Using G4UIExecutive (implemented in all basic examples) : The above code is rather troublesome. This is more convenient way for choosing a session type.

// to include the class definition in the main program:
   #ifdef G4UI_USE
     #include "G4UIExecutive.hh"
   #endif
// to instantiate a session of your choice and start the session
   #ifdef G4UI_USE
     G4UIExecutive* ui = new G4UIExecutive(argc,argv);
     ui->SessionStart();
// the line next to the "SessionStart" is necessary to finish the session
     delete ui;
   #endif

A corresponding environment variable must be preset to select a given interface. But some of them are set by defaults for your convenience.

G4UIterminal, G4UItcsh, G4UIGAG and G4UIGainServer can be used without setting any environment variables. Sessions not needing external packages or libraries are always built (see "G4UI_BUILD.gmk") and linked, so the user can instantiate one of these sessions without rebuilding the libraries and without setting any environment variables.
The environment variable G4UI_USE_XM, G4UI_USE_QT or G4UI_USE_WIN32 must be set to use the respective interface. The file "$G4INSTALL/config/G4UI_USE.gmk" resolves their dependencies on external packages.
If the environment variable G4UI_NONE is set, no external libraries are selected. Also, for your convenience, if any G4UI_USE_XXX environment variable is set, then the corresponding C-pre-processor flag is also set. However, if the environment variable G4UI_NONE is set, no C-pre-processor flags are set.


2.7. How to Make an Executable Program		2.9. How to Execute a Program