1 | <!-- ******************************************************** --> |
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2 | <!-- --> |
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3 | <!-- [History] --> |
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4 | <!-- Changed by: Katsuya Amako, 4-Aug-1998 --> |
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5 | <!-- Changed by: Dennis Wright, 29-Nov-2001 --> |
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6 | <!-- Proof read by: Joe Chuma, 14-Jun-1999 --> |
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7 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
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8 | <!-- --> |
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9 | <!-- ******************************************************** --> |
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10 | |
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11 | |
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12 | <!-- ******************* Section (Level#1) ****************** --> |
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13 | <sect1 id="sect.HowToDefMain"> |
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14 | <title> |
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15 | How to Define the main() Program |
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16 | </title> |
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17 | |
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18 | <!-- ******************* Section (Level#2) ****************** --> |
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19 | <sect2 id="sect.HowToDefMain.SimpleMainMethod"> |
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20 | <title> |
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21 | A Sample <literal>main()</literal> Method |
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22 | </title> |
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23 | |
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24 | <para> |
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25 | The contents of <literal>main()</literal> will vary according to the |
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26 | needs of a given simulation application and therefore must be supplied |
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27 | by the user. The Geant4 toolkit does not provide a <literal>main()</literal> |
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28 | method, but a sample is provided here as a guide to the beginning |
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29 | user. <xref linkend="programlist_HowToDefMain_1" /> is the simplest example of |
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30 | <literal>main()</literal> required to build a simulation program. |
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31 | </para> |
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32 | |
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33 | <example id="programlist_HowToDefMain_1"> |
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34 | <title> |
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35 | Simplest example of <literal>main()</literal> |
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36 | </title> |
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37 | |
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38 | <programlisting> |
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39 | #include "G4RunManager.hh" |
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40 | #include "G4UImanager.hh" |
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41 | |
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42 | #include "ExN01DetectorConstruction.hh" |
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43 | #include "ExN01PhysicsList.hh" |
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44 | #include "ExN01PrimaryGeneratorAction.hh" |
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45 | |
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46 | int main() |
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47 | { |
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48 | // construct the default run manager |
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49 | G4RunManager* runManager = new G4RunManager; |
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50 | |
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51 | // set mandatory initialization classes |
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52 | runManager->SetUserInitialization(new ExN01DetectorConstruction); |
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53 | runManager->SetUserInitialization(new ExN01PhysicsList); |
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54 | |
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55 | // set mandatory user action class |
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56 | runManager->SetUserAction(new ExN01PrimaryGeneratorAction); |
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57 | |
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58 | // initialize G4 kernel |
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59 | runManager->Initialize(); |
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60 | |
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61 | // get the pointer to the UI manager and set verbosities |
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62 | G4UImanager* UI = G4UImanager::GetUIpointer(); |
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63 | UI->ApplyCommand("/run/verbose 1"); |
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64 | UI->ApplyCommand("/event/verbose 1"); |
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65 | UI->ApplyCommand("/tracking/verbose 1"); |
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66 | |
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67 | // start a run |
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68 | int numberOfEvent = 3; |
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69 | runManager->BeamOn(numberOfEvent); |
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70 | |
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71 | // job termination |
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72 | delete runManager; |
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73 | return 0; |
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74 | } |
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75 | </programlisting> |
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76 | </example> |
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77 | |
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78 | <para> |
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79 | The <literal>main()</literal> method is implemented by two toolkit |
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80 | classes, <emphasis>G4RunManager</emphasis> and <emphasis>G4UImanager</emphasis>, |
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81 | and three classes, <emphasis>ExN01DetectorConstruction</emphasis>, |
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82 | <emphasis>ExN01PhysicsList</emphasis> and |
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83 | <emphasis>ExN01PrimaryGeneratorAction</emphasis>, which are derived from |
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84 | toolkit classes. Each of these are explained in the following sections. |
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85 | </para> |
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86 | |
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87 | </sect2> |
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88 | |
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89 | <!-- ******************* Section (Level#2) ****************** --> |
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90 | <sect2 id="sect.HowToDefMain.G4RunManager"> |
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91 | <title> |
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92 | <emphasis>G4RunManager</emphasis> |
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93 | </title> |
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94 | |
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95 | <para> |
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96 | The first thing <literal>main()</literal> must do is create an instance of |
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97 | the <emphasis>G4RunManager</emphasis> class. This is the only manager class in |
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98 | the Geant4 kernel which should be explicitly constructed in the |
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99 | user's <literal>main()</literal>. It controls the flow of the program and |
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100 | manages the event loop(s) within a run. When <emphasis>G4RunManager</emphasis> is |
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101 | created, the other major manager classes are also created. They are |
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102 | deleted automatically when <emphasis>G4RunManager</emphasis> is deleted. The run |
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103 | manager is also responsible for managing initialization procedures, |
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104 | including methods in the user initialization classes. Through these |
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105 | the run manager must be given all the information necessary to |
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106 | build and run the simulation, including |
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107 | </para> |
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108 | |
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109 | <orderedlist spacing="compact"> |
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110 | <listitem><para> |
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111 | how the detector should be constructed, |
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112 | </para></listitem> |
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113 | <listitem><para> |
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114 | all the particles and all the physics processes to be |
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115 | simulated, |
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116 | </para></listitem> |
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117 | <listitem><para> |
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118 | how the primary particle(s) in an event should be produced |
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119 | and |
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120 | </para></listitem> |
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121 | <listitem><para> |
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122 | any additional requirements of the simulation.</para></listitem> |
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123 | </orderedlist> |
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124 | |
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125 | <para> |
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126 | In the sample <literal>main()</literal> the lines |
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127 | |
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128 | <informalexample> |
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129 | <programlisting> |
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130 | runManager->SetUserInitialization(new ExN01DetectorConstruction); |
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131 | runManager->SetUserInitialization(new ExN01PhysicsList); |
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132 | </programlisting> |
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133 | </informalexample> |
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134 | |
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135 | create objects which specify the detector geometry and physics |
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136 | processes, respectively, and pass their pointers to the run |
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137 | manager. <emphasis>ExN01DetectorConstruction</emphasis> is an example of a user |
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138 | initialization class which is derived from |
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139 | <emphasis>G4VUserDetectorConstruction</emphasis>. This is where the user |
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140 | describes the entire detector setup, including |
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141 | </para> |
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142 | |
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143 | <itemizedlist spacing="compact"> |
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144 | <listitem><para> |
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145 | its geometry, |
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146 | </para></listitem> |
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147 | <listitem><para> |
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148 | the materials used in its construction, |
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149 | </para></listitem> |
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150 | <listitem><para> |
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151 | a definition of its sensitive regions and |
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152 | </para></listitem> |
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153 | <listitem><para> |
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154 | the readout schemes of the sensitive regions. |
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155 | </para></listitem> |
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156 | </itemizedlist> |
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157 | |
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158 | <para> |
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159 | Similarly <emphasis>ExN01PhysicsList</emphasis> is derived from |
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160 | <emphasis>G4VUserPhysicsList</emphasis> and requires the user to define |
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161 | </para> |
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162 | |
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163 | <itemizedlist spacing="compact"> |
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164 | <listitem><para> |
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165 | the particles to be used in the simulation, |
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166 | </para></listitem> |
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167 | <listitem><para> |
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168 | the range cuts for these particles and |
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169 | </para></listitem> |
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170 | <listitem><para> |
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171 | all the physics processes to be simulated. |
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172 | </para></listitem> |
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173 | </itemizedlist> |
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174 | |
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175 | <para> |
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176 | The next instruction in <literal>main()</literal> |
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177 | |
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178 | <informalexample> |
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179 | <programlisting> |
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180 | runManager->SetUserAction(new ExN01PrimaryGeneratorAction); |
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181 | </programlisting> |
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182 | </informalexample> |
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183 | |
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184 | creates an instance of a particle generator and passes its pointer |
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185 | to the run manager. <emphasis>ExN01PrimaryGeneratorAction</emphasis> is an |
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186 | example of a user action class which is derived from |
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187 | <emphasis>G4VUserPrimaryGeneratorAction</emphasis>. In this class the user must |
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188 | describe the initial state of the primary event. This class has a |
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189 | public virtual method named <literal>generatePrimaries()</literal> which will |
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190 | be invoked at the beginning of each event. Details will be given in |
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191 | <xref linkend="sect.HowToGenEvent" />. |
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192 | Note that Geant4 does not provide any default behavior for generating a primary event. |
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193 | </para> |
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194 | |
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195 | <para> |
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196 | The next instruction |
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197 | |
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198 | <informalexample> |
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199 | <programlisting> |
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200 | runManager->Initialize(); |
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201 | </programlisting> |
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202 | </informalexample> |
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203 | |
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204 | performs the detector construction, creates the physics processes, |
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205 | calculates cross sections and otherwise sets up the run. The final |
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206 | run manager method in <literal>main()</literal> |
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207 | |
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208 | <informalexample> |
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209 | <programlisting> |
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210 | int numberOfEvent = 3; |
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211 | runManager->beamOn(numberOfEvent); |
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212 | </programlisting> |
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213 | </informalexample> |
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214 | |
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215 | begins a run of three sequentially processed events. The |
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216 | <literal>beamOn()</literal> method may be invoked any number of times within |
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217 | <literal>main()</literal> with each invocation representing a separate run. |
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218 | Once a run has begun neither the detector setup nor the physics |
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219 | processes may be changed. They may be changed between runs, |
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220 | however, as described in <xref linkend="sect.Run.Custom" />. |
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221 | More information on <emphasis>G4RunManager</emphasis> in general is found in |
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222 | <xref linkend="sect.Run" />. |
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223 | </para> |
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224 | |
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225 | <para> |
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226 | As mentioned above, other manager classes are created when the |
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227 | run manager is created. One of these is the user interface manager, |
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228 | <emphasis>G4UImanager</emphasis>. In <literal>main()</literal> a pointer to |
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229 | the interface manager must be obtained |
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230 | |
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231 | <informalexample> |
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232 | <programlisting> |
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233 | G4UImanager* UI = G4UImanager::getUIpointer(); |
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234 | </programlisting> |
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235 | </informalexample> |
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236 | |
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237 | in order for the user to issue commands to the program. In the |
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238 | present example the <literal>applyCommand()</literal> method is called three |
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239 | times to direct the program to print out information at the run, |
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240 | event and tracking levels of simulation. A wide range of commands |
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241 | is available which allows the user detailed control of the |
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242 | simulation. A list of these commands can be found in |
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243 | <xref linkend="sect.BuiltinCom" />. |
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244 | </para> |
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245 | |
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246 | </sect2> |
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247 | |
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248 | |
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249 | <!-- ******************* Section (Level#2) ****************** --> |
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250 | <sect2 id="sect.HowToDefMain.UserInitAction"> |
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251 | <title> |
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252 | User Initialization and Action Classes |
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253 | </title> |
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254 | |
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255 | <!-- ******************* Section (Level#3) ****************** --> |
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256 | <sect3 id="sect.HowToDefMain.UserInitAction.MandatoryUserClasses"> |
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257 | <title> |
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258 | Mandatory User Classes |
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259 | </title> |
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260 | |
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261 | <para> |
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262 | There are three classes which must be defined by the user. Two |
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263 | of them are user initialization classes, and the other is a user |
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264 | action class. They must be derived from the abstract base classes |
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265 | provided by Geant4: <emphasis>G4VUserDetectorConstruction</emphasis>, |
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266 | <emphasis>G4VuserPhysicsList</emphasis> and |
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267 | <emphasis>G4VuserPrimaryGeneratorAction</emphasis>. |
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268 | Geant4 does not provide default behavior for these classes. |
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269 | <emphasis>G4RunManager</emphasis> checks for the existence of these mandatory |
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270 | classes when the <literal>Initialize()</literal> and <literal>BeamOn()</literal> |
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271 | methods are invoked. |
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272 | </para> |
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273 | |
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274 | <para> |
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275 | As mentioned in the previous section, |
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276 | <emphasis>G4VUserDetectorConstruction</emphasis> requires the user to define the |
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277 | detector and <emphasis>G4VUserPhysicsList</emphasis> requires the user to define |
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278 | the physics. Detector definition will be discussed in Sections |
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279 | </para> |
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280 | |
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281 | <para> |
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282 | <xref linkend="sect.HowToDefDetectorGeom" /> and |
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283 | <xref linkend="sect.HowToSpecMate" />. |
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284 | Physics definition will be discussed in Sections |
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285 | <xref linkend="sect.HowToSpecParti" /> |
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286 | and |
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287 | <xref linkend="sect.HowToSpecPhysProc" />. |
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288 | The user action <emphasis>G4VuserPrimaryGeneratorAction</emphasis> |
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289 | requires that the initial event state be defined. Primary event generation will |
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290 | be discussed in |
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291 | <xref linkend="sect.HowToMakeExec" />. |
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292 | </para> |
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293 | |
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294 | </sect3> |
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295 | |
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296 | <!-- ******************* Section (Level#3) ****************** --> |
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297 | <sect3 id="sect.HowToDefMain.UserInitAction.OptionalUserAction"> |
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298 | <title> |
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299 | Optional User Action Classes |
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300 | </title> |
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301 | |
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302 | <para> |
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303 | Geant4 provides five user hook classes: |
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304 | </para> |
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305 | |
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306 | <itemizedlist spacing="compact"> |
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307 | <listitem><para> |
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308 | <emphasis>G4UserRunAction</emphasis> |
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309 | </para></listitem> |
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310 | <listitem><para> |
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311 | <emphasis>G4UserEventAction</emphasis> |
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312 | </para></listitem> |
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313 | <listitem><para> |
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314 | <emphasis>G4UserStackingAction</emphasis> |
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315 | </para></listitem> |
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316 | <listitem><para> |
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317 | <emphasis>G4UserTrackingAction</emphasis> |
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318 | </para></listitem> |
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319 | <listitem><para> |
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320 | <emphasis>G4UserSteppingAction</emphasis> |
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321 | </para></listitem> |
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322 | </itemizedlist> |
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323 | |
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324 | <para> |
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325 | There are several virtual methods in each of these classes which |
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326 | allow the specification of additional procedures at all levels of |
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327 | the simulation application. Details of the user initialization and |
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328 | action classes are provided in |
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329 | <xref linkend="chap.UserActions" />. |
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330 | </para> |
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331 | |
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332 | </sect3> |
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333 | </sect2> |
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334 | |
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335 | <!-- ******************* Section (Level#2) ****************** --> |
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336 | <sect2 id="sect.HowToDefMain.G4UImanagerUICommand"> |
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337 | <title> |
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338 | <emphasis>G4UImanager</emphasis> and UI CommandSubmission |
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339 | </title> |
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340 | |
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341 | <para> |
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342 | Geant4 provides a category named <emphasis role="bold">intercoms</emphasis>. |
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343 | <emphasis>G4UImanager</emphasis> is the manager class of this category. Using the |
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344 | functionalities of this category, you can invoke |
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345 | <emphasis role="bold">set</emphasis> methods |
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346 | of class objects of which you do not know the pointer. |
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347 | In <xref linkend="programlist_HowToDefMain_2" />, |
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348 | the verbosities of various Geant4 manager classes |
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349 | are set. Detailed mechanism description and usage of |
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350 | <emphasis role="bold">intercoms</emphasis> will be given in the next chapter, |
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351 | with a list of available commands. Command submission can be done all through the |
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352 | application. |
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353 | </para> |
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354 | |
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355 | <example id="programlist_HowToDefMain_2"> |
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356 | <title> |
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357 | An example of <literal>main()</literal> using interactive |
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358 | terminal and visualization. Code modified from the previous |
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359 | example are shown in <emphasis role="color_blue">blue</emphasis>. |
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360 | </title> |
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361 | <programlisting> |
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362 | #include "G4RunManager.hh" |
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363 | #include "G4UImanager.hh" |
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364 | <emphasis role="color_blue">#include "G4UIterminal.hh"</emphasis> |
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365 | #include "G4VisExecutive.hh" |
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366 | |
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367 | #include "N02DetectorConstruction.hh" |
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368 | #include "N02PhysicsList.hh" |
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369 | #include "N02PrimaryGeneratorAction.hh" |
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370 | #include "N02RunAction.hh" |
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371 | #include "N02EventAction.hh" |
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372 | #include "N02SteppingAction.hh" |
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373 | |
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374 | #include "g4templates.hh" |
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375 | |
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376 | int main(int argc,char** argv) |
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377 | { |
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378 | // construct the default run manager |
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379 | G4RunManager * runManager = new G4RunManager; |
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380 | |
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381 | // set mandatory initialization classes |
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382 | N02DetectorConstruction* detector = new N02DetectorConstruction; |
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383 | runManager->SetUserInitialization(detector); |
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384 | runManager->SetUserInitialization(new N02PhysicsList); |
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385 | |
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386 | // visualization manager |
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387 | G4VisManager* visManager = new G4VisExecutive; |
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388 | visManager->Initialize(); |
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389 | |
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390 | // set user action classes |
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391 | runManager->SetUserAction(new N02PrimaryGeneratorAction(detector)); |
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392 | runManager->SetUserAction(new N02RunAction); |
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393 | runManager->SetUserAction(new N02EventAction); |
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394 | runManager->SetUserAction(new N02SteppingAction); |
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395 | |
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396 | // get the pointer to the User Interface manager |
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397 | G4UImanager* UI = G4UImanager::GetUIpointer(); |
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398 | |
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399 | <emphasis role="color_blue"> |
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400 | if(argc==1) |
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401 | // Define (G)UI terminal for interactive mode |
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402 | { |
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403 | G4UIsession * session = new G4UIterminal; |
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404 | UI->ApplyCommand("/control/execute prerun.g4mac"); |
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405 | session->sessionStart(); |
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406 | delete session; |
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407 | } |
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408 | else |
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409 | // Batch mode |
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410 | { |
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411 | G4String command = "/control/execute "; |
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412 | G4String fileName = argv[1]; |
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413 | UI->ApplyCommand(command+fileName); |
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414 | } |
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415 | </emphasis> |
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416 | |
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417 | // job termination |
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418 | delete visManager; |
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419 | delete runManager; |
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420 | |
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421 | return 0; |
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422 | } |
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423 | </programlisting> |
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424 | </example> |
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425 | |
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426 | |
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427 | </sect2> |
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428 | |
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429 | |
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430 | <!-- ******************* Section (Level#2) ****************** --> |
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431 | <sect2 id="sect.HowToDefMain.G4coutG4cerr"> |
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432 | <title> |
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433 | <emphasis>G4cout</emphasis> and <emphasis>G4cerr</emphasis> |
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434 | </title> |
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435 | |
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436 | <para> |
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437 | Although not yet included in the above examples, output streams |
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438 | will be needed. <emphasis>G4cout</emphasis> and <emphasis>G4cerr</emphasis> |
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439 | are <emphasis role="bold">iostream</emphasis> |
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440 | objects defined by Geant4. The usage of these objects is exactly |
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441 | the same as the ordinary <emphasis>cout</emphasis> and |
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442 | <emphasis>cerr</emphasis>, |
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443 | except that the output streams will be handled by |
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444 | <emphasis>G4UImanager</emphasis>. |
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445 | Thus, output strings may be displayed on another window or stored in a |
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446 | file. Manipulation of these output streams will be described in |
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447 | <xref linkend="sect.UIDefNew.HowCont" />. |
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448 | These objects should be used instead of the ordinary |
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449 | <emphasis>cout</emphasis> and <emphasis>cerr</emphasis>. |
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450 | </para> |
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451 | |
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452 | |
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453 | </sect2> |
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454 | </sect1> |
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