[904] | 1 | <!-- ******************************************************** --> |
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| 2 | <!-- --> |
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| 3 | <!-- [History] --> |
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| 4 | <!-- Changed by: Katsuya Amako, 21-Sep-1998 --> |
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| 5 | <!-- Changed by: Katsuya Amako, 9-Jul-1998 --> |
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| 6 | <!-- Proof read by: Joe Chuma, 2-Jul-1999 --> |
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| 7 | <!-- Changed by: Katsuya Amako, 15-Jul-2000 --> |
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| 8 | <!-- Changed by: Dennis Wright, 29-Nov-2001 --> |
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| 9 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
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| 10 | <!-- --> |
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| 11 | <!-- ******************************************************** --> |
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| 12 | |
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| 13 | |
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| 14 | <!-- ******************* Section (Level#1) ****************** --> |
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| 15 | <sect1 id="sect.GlobClass"> |
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| 16 | <title> |
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| 17 | Global Usage Classes |
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| 18 | </title> |
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| 19 | |
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| 20 | <para> |
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| 21 | The "global" category in Geant4 collects all classes, types, |
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| 22 | structures and constants which are considered of general use within |
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| 23 | the Geant4 toolkit. This category also defines the interface with |
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| 24 | third-party software libraries (CLHEP, STL, etc.) and |
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| 25 | system-related types, by defining, where appropriate, |
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| 26 | <literal>typedef</literal>s according to the Geant4 code conventions. |
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| 27 | </para> |
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| 28 | |
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| 29 | <!-- ******************* Section (Level#2) ****************** --> |
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| 30 | <sect2 id="sect.GlobClass.SignClass"> |
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| 31 | <title> |
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| 32 | Signature of Geant4 classes |
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| 33 | </title> |
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| 34 | |
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| 35 | <para> |
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| 36 | In order to keep an homogeneous naming style, and according to |
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| 37 | the Geant4 coding style conventions, each class part of the Geant4 |
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| 38 | kernel has its name beginning with the prefix <emphasis>G4</emphasis>, e.g., |
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| 39 | <emphasis>G4VHit, G4GeometryManager, G4ProcessVector,</emphasis> etc. Instead of |
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| 40 | the raw C types, <emphasis>G4</emphasis> types are used within the Geant4 code. |
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| 41 | For the basic numeric types (<literal>int, float, double,</literal> etc.), |
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| 42 | different compilers and different platforms provide different value |
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| 43 | ranges. In order to assure portability, the use of <emphasis>G4int, |
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| 44 | G4float, G4double,</emphasis> which are base classes globally defined, is |
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| 45 | preferable. <emphasis>G4</emphasis> types implement the right generic type for a |
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| 46 | given architecture. |
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| 47 | </para> |
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| 48 | |
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| 49 | <!-- ******************* Section (Level#3) ****************** --> |
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| 50 | <sect3 id="sect.GlobClass.SignClass.BasicType"> |
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| 51 | <title> |
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| 52 | Basic types |
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| 53 | </title> |
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| 54 | |
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| 55 | <para> |
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| 56 | The basic types in Geant4 are considered to be the |
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| 57 | following: |
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| 58 | |
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| 59 | <itemizedlist spacing="compact"> |
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| 60 | <listitem><para> |
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| 61 | <emphasis>G4int</emphasis>, |
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| 62 | </para></listitem> |
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| 63 | <listitem><para> |
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| 64 | <emphasis>G4long</emphasis>, |
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| 65 | </para></listitem> |
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| 66 | <listitem><para> |
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| 67 | <emphasis>G4float</emphasis>, |
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| 68 | </para></listitem> |
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| 69 | <listitem><para> |
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| 70 | <emphasis>G4double</emphasis>, |
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| 71 | </para></listitem> |
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| 72 | <listitem><para> |
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| 73 | <emphasis>G4bool</emphasis>, |
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| 74 | </para></listitem> |
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| 75 | <listitem><para> |
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| 76 | <emphasis>G4complex</emphasis>, |
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| 77 | </para></listitem> |
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| 78 | <listitem><para> |
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| 79 | <emphasis>G4String</emphasis>. |
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| 80 | </para></listitem> |
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| 81 | </itemizedlist> |
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| 82 | |
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| 83 | which currently consist of simple <literal>typedef</literal>s to |
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| 84 | respective types defined in the <emphasis role="bold">CLHEP</emphasis>, |
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| 85 | <emphasis role="bold">STL</emphasis> or system |
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| 86 | libraries. Most definitions of these basic types come with the |
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| 87 | inclusion of a single header file, <literal>globals.hh</literal>. This file |
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| 88 | also provides inclusion of required system headers, as well as some |
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| 89 | global utility functions needed and used within the Geant4 |
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| 90 | kernel. |
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| 91 | </para> |
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| 92 | |
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| 93 | </sect3> |
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| 94 | |
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| 95 | <!-- ******************* Section (Level#3) ****************** --> |
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| 96 | <sect3 id="sect.GlobClass.SignClass.Typedefs"> |
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| 97 | <title> |
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| 98 | Typedefs to CLHEP classes and their usage |
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| 99 | </title> |
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| 100 | |
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| 101 | <para> |
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| 102 | The following classes are <literal>typedef</literal>s to the corresponding |
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| 103 | classes of the <emphasis role="bold">CLHEP</emphasis> |
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| 104 | (<emphasis role="bold">Computing Library for High Energy Physics</emphasis>) |
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| 105 | distribution. For more detailed documentation please refer to the |
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| 106 | <ulink url="http://cern.ch/clhep/manual/RefGuide/"> |
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| 107 | <emphasis role="bold">CLHEP reference guide</emphasis> |
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| 108 | </ulink> |
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| 109 | and the |
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| 110 | <ulink url="http://cern.ch/clhep/manual/UserGuide/"> |
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| 111 | <emphasis role="bold">CLHEP user manual</emphasis> |
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| 112 | </ulink> |
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| 113 | . |
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| 114 | |
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| 115 | <itemizedlist spacing="compact"> |
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| 116 | <listitem><para> |
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| 117 | <emphasis>G4ThreeVector, G4RotationMatrix, G4LorentzVector</emphasis> and |
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| 118 | <emphasis>G4LorentzRotation</emphasis> |
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| 119 | <para> |
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| 120 | Vector classes: defining 3-component (x,y,z) vector entities, |
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| 121 | rotation of such objects as 3x3 matrices, |
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| 122 | 4-component (x,y,z,t) vector entities and their rotation as 4x4 matrices. |
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| 123 | </para> |
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| 124 | </para></listitem> |
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| 125 | <listitem><para> |
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| 126 | <emphasis>G4Plane3D, G4Transform3D, G4Normal3D, G4Point3D</emphasis>, and |
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| 127 | <emphasis>G4Vector3D</emphasis> |
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| 128 | <para> |
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| 129 | Geometrical classes: defining geometrical entities and |
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| 130 | transformations in 3D space. |
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| 131 | </para> |
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| 132 | </para></listitem> |
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| 133 | </itemizedlist> |
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| 134 | </para> |
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| 135 | |
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| 136 | </sect3> |
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| 137 | </sect2> |
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| 138 | |
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| 139 | |
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| 140 | <!-- ******************* Section (Level#2) ****************** --> |
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| 141 | <sect2 id="sect.GlobClass.HEPRandom"> |
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| 142 | <title> |
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| 143 | The <emphasis>HEPRandom</emphasis> module in CLHEP |
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| 144 | </title> |
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| 145 | |
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| 146 | <para> |
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| 147 | The <emphasis>HEPRandom</emphasis> module, originally part of the Geant4 |
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| 148 | kernel, and now distributed as a module of <emphasis |
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| 149 | role="bold">CLHEP</emphasis>, |
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| 150 | has been designed and developed starting from the <emphasis>Random</emphasis> |
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| 151 | class of MC++, the original <emphasis role="bold">CLHEP</emphasis>'s |
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| 152 | <emphasis>HepRandom</emphasis> module and the |
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| 153 | <emphasis role="bold">Rogue Wave</emphasis> approach in the |
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| 154 | <emphasis role="bold">Math.h++</emphasis> package. For |
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| 155 | detailed documentation on the <emphasis>HEPRandom</emphasis> classes see the |
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| 156 | |
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| 157 | <ulink url="http://cern.ch/clhep/manual/RefGuide/"> |
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| 158 | <emphasis role="bold">CLHEP reference guide</emphasis> |
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| 159 | </ulink> |
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| 160 | and the |
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| 161 | <ulink url="http://cern.ch/clhep/manual/UserGuide/"> |
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| 162 | <emphasis role="bold">CLHEP user manual</emphasis> |
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| 163 | </ulink> |
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| 164 | . |
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| 165 | </para> |
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| 166 | |
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| 167 | <para> |
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| 168 | Information written in this manual is extracted from the |
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| 169 | original |
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| 170 | <ulink url="http://cern.ch/clhep/manual/UserGuide/Random/Random.html"> |
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| 171 | manifesto |
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| 172 | </ulink> |
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| 173 | distributed with the <emphasis>HEPRandom</emphasis> |
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| 174 | package.</para> |
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| 175 | |
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| 176 | <para> |
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| 177 | The <emphasis>HEPRandom</emphasis> module consists of classes implementing |
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| 178 | different random ``engines'' and different random |
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| 179 | ``distributions''. A distribution associated to an engine |
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| 180 | constitutes a random ``generator''. A distribution class can |
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| 181 | collect different algorithms and different calling sequences for |
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| 182 | each method to define distribution parameters or range-intervals. |
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| 183 | An engine implements the basic algorithm for pseudo-random numbers |
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| 184 | generation. |
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| 185 | </para> |
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| 186 | |
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| 187 | <para> |
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| 188 | There are 3 different ways of shooting random values: |
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| 189 | |
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| 190 | <orderedlist spacing="compact"> |
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| 191 | <listitem><para> |
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| 192 | Using the static generator defined in the <emphasis>HepRandom</emphasis> |
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| 193 | class: random values are shot using static methods <literal>shoot()</literal> |
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| 194 | defined for each distribution class. The static generator will use, |
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| 195 | as default engine, a <emphasis>HepJamesRandom</emphasis> object, and the user can |
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| 196 | set its properties or change it with a new instantiated engine |
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| 197 | object by using the static methods defined in the <emphasis>HepRandom</emphasis> |
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| 198 | class. |
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| 199 | </para></listitem> |
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| 200 | <listitem><para> |
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| 201 | Skipping the static generator and specifying an engine object: |
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| 202 | random values are shot using static methods |
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| 203 | <literal>shoot(*HepRandomEngine)</literal> defined for each distribution |
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| 204 | class. The user must instantiate an engine object and give it as |
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| 205 | argument to the shoot method. The generator mechanism will then be |
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| 206 | by-passed by using the basic <literal>flat()</literal> method of the |
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| 207 | specified engine. The user must take care of the engine objects |
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| 208 | he/she instantiates. |
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| 209 | </para></listitem> |
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| 210 | <listitem><para> |
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| 211 | Skipping the static generator and instantiating a distribution |
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| 212 | object: random values are shot using <literal>fire()</literal> methods (NOT |
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| 213 | static) defined for each distribution class. The user must |
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| 214 | instantiate a distribution object giving as argument to the |
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| 215 | constructor an engine by pointer or by reference. By doing so, the |
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| 216 | engine will be associated to the distribution object and the |
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| 217 | generator mechanism will be by-passed by using the basic |
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| 218 | <literal>flat()</literal> method of that engine. |
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| 219 | </para></listitem> |
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| 220 | </orderedlist> |
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| 221 | </para> |
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| 222 | |
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| 223 | <para> |
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| 224 | In this guide, we'll only focus on the static generator (point |
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| 225 | 1.), since the static interface of <emphasis>HEPRandom</emphasis> is the only one |
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| 226 | used within the Geant4 toolkit. |
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| 227 | </para> |
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| 228 | |
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| 229 | <!-- ******************* Section (Level#3) ****************** --> |
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| 230 | <sect3 id="sect.GlobClass.HEPRandom.Engines"> |
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| 231 | <title> |
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| 232 | <emphasis>HEPRandom</emphasis> engines |
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| 233 | </title> |
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| 234 | |
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| 235 | <para> |
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| 236 | The class <emphasis>HepRandomEngine</emphasis> is the abstract class defining |
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| 237 | the interface for each random engine. It implements the |
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| 238 | <literal>getSeed()</literal> and <literal>getSeeds()</literal> methods which return the |
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| 239 | `initial seed' value and the initial array of seeds (if any) |
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| 240 | respectively. Many concrete random engines can be defined and added |
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| 241 | to the structure, simply making them inheriting from |
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| 242 | <emphasis>HepRandomEngine</emphasis>. Several different engines are currently |
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| 243 | implemented in <emphasis>HepRandom</emphasis>, we describe here five of them: |
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| 244 | |
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| 245 | <itemizedlist spacing="compact"> |
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| 246 | <listitem><para> |
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| 247 | <emphasis>HepJamesRandom</emphasis> |
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| 248 | <para> |
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| 249 | It implements the algorithm described in ``F.James, Comp. Phys. |
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| 250 | Comm. 60 (1990) 329'' for pseudo-random number generation. This is |
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| 251 | the default random engine for the static generator; it will be |
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| 252 | invoked by each distribution class unless the user sets a different one. |
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| 253 | </para> |
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| 254 | </para></listitem> |
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| 255 | <listitem><para> |
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| 256 | <emphasis>DRand48Engine</emphasis> |
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| 257 | <para> |
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| 258 | Random engine using the <literal>drand48()</literal> and |
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| 259 | <literal>srand48()</literal> system functions from C standard library to |
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| 260 | implement the <literal>flat()</literal> basic distribution and for setting |
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| 261 | seeds respectively. <emphasis>DRand48Engine</emphasis> uses the |
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| 262 | <literal>seed48()</literal> |
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| 263 | function from C standard library to retrieve the current internal |
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| 264 | status of the generator, which is represented by 3 short values. |
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| 265 | <emphasis>DRand48Engine</emphasis> is the only engine defined in |
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| 266 | <emphasis>HEPRandom</emphasis> |
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| 267 | which intrinsically works in 32 bits precision. Copies of an object |
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| 268 | of this kind are not allowed. |
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| 269 | </para> |
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| 270 | </para></listitem> |
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| 271 | <listitem><para> |
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| 272 | <emphasis>RandEngine</emphasis> |
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| 273 | <para> |
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| 274 | Simple random engine using the <literal>rand()</literal> and |
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| 275 | <literal>srand()</literal> system functions from the C standard library to |
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| 276 | implement the <literal>flat()</literal> basic distribution and for setting |
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| 277 | seeds respectively. Please note that it's well known that the |
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| 278 | spectral properties of <literal>rand()</literal> leave a great deal to be |
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| 279 | desired, therefore the usage of this engine is not recommended if a |
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| 280 | good randomness quality or a long period is required in your code. |
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| 281 | Copies of an object of this kind are not allowed. |
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| 282 | </para> |
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| 283 | </para></listitem> |
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| 284 | <listitem><para> |
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| 285 | <emphasis>RanluxEngine</emphasis> |
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| 286 | <para> |
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| 287 | The algorithm for <emphasis>RanluxEngine</emphasis> has been taken from the |
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| 288 | original implementation in FORTRAN77 by Fred James, part of the |
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| 289 | <emphasis role="bold">MATHLIB HEP</emphasis> library. The initialisation is |
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| 290 | carried out using |
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| 291 | a Multiplicative Congruential generator using formula constants of |
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| 292 | L'Ecuyer as described in ``F.James, Comp. Phys. Comm. 60 (1990) |
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| 293 | 329-344''. The engine provides five different luxury levels for |
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| 294 | quality of random generation. When instantiating a |
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| 295 | <emphasis>RanluxEngine</emphasis>, the user can specify the luxury level to the |
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| 296 | constructor (if not, the default value 3 is taken). For example: |
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| 297 | |
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| 298 | <informalexample> |
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| 299 | <programlisting> |
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| 300 | RanluxEngine theRanluxEngine(seed,4); |
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| 301 | // instantiates an engine with `seed' and the best luxury-level |
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| 302 | ... or |
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| 303 | RanluxEngine theRanluxEngine; |
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| 304 | // instantiates an engine with default seed value and luxury-level |
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| 305 | ... |
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| 306 | </programlisting> |
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| 307 | </informalexample> |
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| 308 | |
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| 309 | The class provides a <literal>getLuxury()</literal> method to get the |
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| 310 | engine luxury level. |
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| 311 | </para> |
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| 312 | <para> |
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| 313 | The <literal>SetSeed()</literal> and <literal>SetSeeds()</literal> |
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| 314 | methods to set the initial seeds for the engine, can be invoked specifying |
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| 315 | the luxury level. For example: |
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| 316 | |
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| 317 | <informalexample> |
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| 318 | <programlisting> |
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| 319 | // static interface |
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| 320 | HepRandom::setTheSeed(seed,4); // sets the seed to `seed' and luxury to 4 |
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| 321 | HepRandom::setTheSeed(seed); // sets the seed to `seed' keeping |
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| 322 | // the current luxury level |
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| 323 | </programlisting> |
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| 324 | </informalexample> |
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| 325 | </para> |
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| 326 | </para></listitem> |
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| 327 | <listitem><para> |
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| 328 | <emphasis>RanecuEngine</emphasis> |
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| 329 | <para> |
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| 330 | The algorithm for <emphasis>RanecuEngine</emphasis> is taken from the one |
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| 331 | originally written in FORTRAN77 as part of the |
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| 332 | <emphasis role="bold">MATHLIB HEP</emphasis> |
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| 333 | library. The initialisation is carried out using a Multiplicative |
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| 334 | Congruential generator using formula constants of L'Ecuyer as |
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| 335 | described in ``F.James, Comp. Phys. Comm. 60 (1990) 329-344''. |
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| 336 | Handling of seeds for this engine is slightly different than the |
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| 337 | other engines in <emphasis>HEPRandom</emphasis>. Seeds are taken from a seed |
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| 338 | table given an index, the <literal>getSeed()</literal> method returns the |
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| 339 | current index of seed table. The <literal>setSeeds()</literal> method will |
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| 340 | set seeds in the local <literal>SeedTable</literal> at a given position index |
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| 341 | (if the index number specified exceeds the table's size, |
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| 342 | <literal>[index%size]</literal> is taken). For example: |
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| 343 | |
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| 344 | <informalexample> |
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| 345 | <programlisting> |
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| 346 | // static interface |
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| 347 | const G4long* table_entry; |
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| 348 | table_entry = HepRandom::getTheSeeds(); |
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| 349 | // it returns a pointer `table_entry' to the local SeedTable |
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| 350 | // at the current `index' position. The couple of seeds |
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| 351 | // accessed represents the current `status' of the engine itself ! |
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| 352 | ... |
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| 353 | G4int index=n; |
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| 354 | G4long seeds[2]; |
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| 355 | HepRandom::setTheSeeds(seeds,index); |
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| 356 | // sets the new `index' for seeds and modify the values inside |
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| 357 | // the local SeedTable at the `index' position. If the index |
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| 358 | // is not specified, the current index in the table is considered. |
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| 359 | ... |
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| 360 | </programlisting> |
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| 361 | </informalexample> |
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| 362 | </para> |
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| 363 | |
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| 364 | <para> |
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| 365 | The <literal>setSeed()</literal> method resets the current `status' of the |
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| 366 | engine to the original seeds stored in the static table of seeds in |
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| 367 | <emphasis>HepRandom</emphasis>, at the specified index. |
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| 368 | </para> |
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| 369 | </para></listitem> |
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| 370 | </itemizedlist> |
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| 371 | </para> |
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| 372 | |
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| 373 | <para> |
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| 374 | Except for the <emphasis>RanecuEngine</emphasis>, for which the internal |
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| 375 | status is represented by just a couple of longs, all the other |
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| 376 | engines have a much more complex representation of their internal |
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| 377 | status, which currently can be obtained only through the methods |
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| 378 | <literal>saveStatus()</literal>, <literal>restoreStatus()</literal> and |
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| 379 | <literal>showStatus()</literal>, which can also be statically called from |
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| 380 | <emphasis>HepRandom</emphasis>. The status of the generator is needed for example |
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| 381 | to be able to reproduce a run or an event in a run at a given stage |
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| 382 | of the simulation. |
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| 383 | </para> |
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| 384 | |
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| 385 | <para> |
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| 386 | <emphasis>RanecuEngine</emphasis> is probably the most suitable engine for |
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| 387 | this kind of operation, since its internal status can be |
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| 388 | fetched/reset by simply using |
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| 389 | <literal>getSeeds()</literal>/<literal>setSeeds()</literal> |
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| 390 | (<literal>getTheSeeds()</literal>/<literal>setTheSeeds()</literal> for the static |
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| 391 | interface in <emphasis>HepRandom</emphasis>). |
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| 392 | </para> |
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| 393 | |
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| 394 | </sect3> |
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| 395 | |
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| 396 | |
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| 397 | <!-- ******************* Section (Level#3) ****************** --> |
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| 398 | <sect3 id="sect.GlobClass.HEPRandom.StaticInt"> |
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| 399 | <title> |
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| 400 | The static interface in the <emphasis>HepRandom</emphasis> class |
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| 401 | </title> |
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| 402 | |
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| 403 | <para> |
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| 404 | <emphasis>HepRandom</emphasis> a singleton class and using a |
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| 405 | <emphasis>HepJamesRandom</emphasis> engine as default algorithm for pseudo-random |
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| 406 | number generation. <emphasis>HepRandom</emphasis> defines a static private data |
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| 407 | member, <literal>theGenerator</literal>, and a set of static methods to |
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| 408 | manipulate it. By means of <literal>theGenerator</literal>, the user can |
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| 409 | change the underlying engine algorithm, get and set the seeds, and |
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| 410 | use any kind of defined random distribution. The static methods |
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| 411 | <literal>setTheSeed()</literal> and <literal>getTheSeed()</literal> will set and get |
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| 412 | respectively the `initial' seed to the main engine used by the |
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| 413 | static generator. For example: |
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| 414 | |
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| 415 | <informalexample> |
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| 416 | <programlisting> |
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| 417 | HepRandom::setTheSeed(seed); // to change the current seed to 'seed' |
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| 418 | int startSeed = HepRandom::getTheSeed(); // to get the current initial seed |
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| 419 | HepRandom::saveEngineStatus(); // to save the current engine status on file |
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| 420 | HepRandom::restoreEngineStatus(); // to restore the current engine to a previous |
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| 421 | // saved configuration |
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| 422 | HepRandom::showEngineStatus(); // to display the current engine status to stdout |
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| 423 | ... |
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| 424 | int index=n; |
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| 425 | long seeds[2]; |
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| 426 | HepRandom::getTheTableSeeds(seeds,index); |
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| 427 | // fills `seeds' with the values stored in the global |
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| 428 | // seedTable at position `index' |
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| 429 | </programlisting> |
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| 430 | </informalexample> |
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| 431 | </para> |
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| 432 | |
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| 433 | <para> |
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| 434 | Only one random engine can be active at a time, the user can |
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| 435 | decide at any time to change it, define a new one (if not done |
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| 436 | already) and set it. For example: |
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| 437 | |
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| 438 | <informalexample> |
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| 439 | <programlisting> |
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| 440 | RanecuEngine theNewEngine; |
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| 441 | HepRandom::setTheEngine(&theNewEngine); |
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| 442 | ... |
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| 443 | </programlisting> |
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| 444 | </informalexample> |
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| 445 | |
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| 446 | or simply setting it to an old instantiated engine (the old |
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| 447 | engine status is kept and the new random sequence will start |
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| 448 | exactly from the last one previously interrupted). For example: |
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| 449 | |
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| 450 | <informalexample> |
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| 451 | <programlisting> |
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| 452 | HepRandom::setTheEngine(&myOldEngine); |
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| 453 | </programlisting> |
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| 454 | </informalexample> |
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| 455 | </para> |
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| 456 | |
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| 457 | <para> |
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| 458 | Other static methods defined in this class are: |
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| 459 | |
---|
| 460 | <itemizedlist spacing="compact"> |
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| 461 | <listitem><para> |
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| 462 | <literal>void setTheSeeds(const G4long* seeds, G4int)</literal> |
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| 463 | </para></listitem> |
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| 464 | <listitem><para> |
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| 465 | <literal>const G4long* getTheSeeds()</literal> |
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| 466 | <para> |
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| 467 | To set/get an array of seeds for the generator, in the case of a |
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| 468 | <emphasis>RanecuEngine</emphasis> this corresponds also to set/get the current |
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| 469 | status of the engine. |
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| 470 | </para> |
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| 471 | </para></listitem> |
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| 472 | <listitem><para> |
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| 473 | <literal>HepRandomEngine* getTheEngine()</literal> |
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| 474 | <para> |
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| 475 | To get a pointer to the current engine used by the static |
---|
| 476 | generator. |
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| 477 | </para> |
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| 478 | </para></listitem> |
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| 479 | </itemizedlist> |
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| 480 | </para> |
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| 481 | |
---|
| 482 | </sect3> |
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| 483 | |
---|
| 484 | <!-- ******************* Section (Level#3) ****************** --> |
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| 485 | <sect3 id="sect.GlobClass.HEPRandom.Distri"> |
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| 486 | <title> |
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| 487 | <emphasis>HEPRandom</emphasis> distributions |
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| 488 | </title> |
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| 489 | |
---|
| 490 | <para> |
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| 491 | A distribution-class can collect different algorithms and |
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| 492 | different calling sequences for each method to define distribution |
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| 493 | parameters or range-intervals; it also collects methods to fill |
---|
| 494 | arrays, of specified size, of random values, according to the |
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| 495 | distribution. This class collects either static and not static |
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| 496 | methods. A set of distribution classes are defined in |
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| 497 | <emphasis>HEPRandom</emphasis>. Here is the description of some of them: |
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| 498 | |
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| 499 | <itemizedlist spacing="compact"> |
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| 500 | <listitem><para> |
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| 501 | <emphasis>RandFlat</emphasis> |
---|
| 502 | <para> |
---|
| 503 | Class to shoot flat random values (integers or double) within a |
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| 504 | specified interval. The class provides also methods to shoot just |
---|
| 505 | random bits. |
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| 506 | </para> |
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| 507 | </para></listitem> |
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| 508 | <listitem><para> |
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| 509 | <emphasis>RandExponential</emphasis> |
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| 510 | <para> |
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| 511 | Class to shoot exponential distributed random values, given a |
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| 512 | mean (default mean = 1) |
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| 513 | </para> |
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| 514 | </para></listitem> |
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| 515 | <listitem><para> |
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| 516 | <emphasis>RandGauss</emphasis> |
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| 517 | <para> |
---|
| 518 | Class to shoot Gaussian distributed random values, given a mean |
---|
| 519 | (default = 0) or specifying also a deviation (default = 1). |
---|
| 520 | Gaussian random numbers are generated two at the time, so every |
---|
| 521 | other time a number is shot, the number returned is the one |
---|
| 522 | generated the time before. |
---|
| 523 | </para> |
---|
| 524 | </para></listitem> |
---|
| 525 | <listitem><para> |
---|
| 526 | <emphasis>RandBreitWigner</emphasis> |
---|
| 527 | <para> |
---|
| 528 | Class to shoot numbers according to the Breit-Wigner |
---|
| 529 | distribution algorithms (plain or mean^2). |
---|
| 530 | </para> |
---|
| 531 | </para></listitem> |
---|
| 532 | <listitem><para> |
---|
| 533 | <emphasis>RandPoisson</emphasis> |
---|
| 534 | <para> |
---|
| 535 | Class to shoot numbers according to the Poisson distribution, |
---|
| 536 | given a mean (default = 1) (Algorithm taken from ``W.H.Press et |
---|
| 537 | al., Numerical Recipes in C, Second Edition''). |
---|
| 538 | </para> |
---|
| 539 | </para></listitem> |
---|
| 540 | </itemizedlist> |
---|
| 541 | </para> |
---|
| 542 | |
---|
| 543 | </sect3> |
---|
| 544 | </sect2> |
---|
| 545 | |
---|
| 546 | |
---|
| 547 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 548 | <sect2 id="sect.HEPNumerics"> |
---|
| 549 | <title> |
---|
| 550 | The <emphasis>HEPNumerics</emphasis> module |
---|
| 551 | </title> |
---|
| 552 | |
---|
| 553 | <para> |
---|
| 554 | A set of classes implementing numerical algorithms has been |
---|
| 555 | developed in Geant4. Most of the algorithms and methods have been |
---|
| 556 | implemented mainly based on recommendations given in the books: |
---|
| 557 | |
---|
| 558 | <itemizedlist spacing="compact"> |
---|
| 559 | <listitem><para> |
---|
| 560 | B.H. Flowers, ``An introduction to Numerical Methods In C++'', |
---|
| 561 | Claredon Press, Oxford 1995. |
---|
| 562 | </para></listitem> |
---|
| 563 | <listitem><para> |
---|
| 564 | M. Abramowitz, I. Stegun, ``Handbook of mathematical |
---|
| 565 | functions'', DOVER Publications INC, New York 1965 ; chapters 9, |
---|
| 566 | 10, and 22. |
---|
| 567 | </para></listitem> |
---|
| 568 | </itemizedlist> |
---|
| 569 | </para> |
---|
| 570 | |
---|
| 571 | <para> |
---|
| 572 | This set of classes includes: |
---|
| 573 | |
---|
| 574 | <itemizedlist spacing="compact"> |
---|
| 575 | <listitem><para> |
---|
| 576 | <emphasis>G4ChebyshevApproximation</emphasis> |
---|
| 577 | <para> |
---|
| 578 | Class creating the Chebyshev approximation for a function |
---|
| 579 | pointed by fFunction data member. The Chebyshev polynomial |
---|
| 580 | approximation provides an efficient evaluation of the minimax |
---|
| 581 | polynomial, which (among all polynomials of the same degree) has |
---|
| 582 | the smallest maximum deviation from the true function. |
---|
| 583 | </para> |
---|
| 584 | </para></listitem> |
---|
| 585 | <listitem><para> |
---|
| 586 | <emphasis>G4DataInterpolation</emphasis> |
---|
| 587 | <para> |
---|
| 588 | Class providing methods for data interpolations and |
---|
| 589 | extrapolations: Polynomial, Cubic Spline, ... |
---|
| 590 | </para> |
---|
| 591 | </para></listitem> |
---|
| 592 | <listitem><para> |
---|
| 593 | <emphasis>G4GaussChebyshevQ</emphasis> |
---|
| 594 | </para></listitem> |
---|
| 595 | <listitem><para> |
---|
| 596 | <emphasis>G4GaussHermiteQ</emphasis> |
---|
| 597 | </para></listitem> |
---|
| 598 | <listitem><para> |
---|
| 599 | <emphasis>G4GaussJacobiQ</emphasis> |
---|
| 600 | </para></listitem> |
---|
| 601 | <listitem><para> |
---|
| 602 | <emphasis>G4GaussLaguerreQ</emphasis> |
---|
| 603 | <para> |
---|
| 604 | Classes implementing the Gauss-Chebyshev, Gauss-Hermite, |
---|
| 605 | Gauss-Jacobi, Gauss-Laguerre and Gauss-Legendre quadrature methods. |
---|
| 606 | Roots of orthogonal polynomials and corresponding weights are |
---|
| 607 | calculated based on iteration method (by bisection Newton |
---|
| 608 | algorithm). |
---|
| 609 | </para> |
---|
| 610 | </para></listitem> |
---|
| 611 | <listitem><para> |
---|
| 612 | <emphasis>G4Integrator</emphasis> |
---|
| 613 | <para> |
---|
| 614 | Template class collecting integrator methods for generic |
---|
| 615 | functions (Legendre, Simpson, Adaptive Gauss, Laguerre, Hermite, |
---|
| 616 | Jacobi). |
---|
| 617 | </para> |
---|
| 618 | </para></listitem> |
---|
| 619 | <listitem><para> |
---|
| 620 | <emphasis>G4SimpleIntegration</emphasis> |
---|
| 621 | <para> |
---|
| 622 | Class implementing simple numerical methods (Trapezoidal, |
---|
| 623 | MidPoint, Gauss, Simpson, Adaptive Gauss, for integration of |
---|
| 624 | functions with signature: double f(double). |
---|
| 625 | </para> |
---|
| 626 | </para></listitem> |
---|
| 627 | </itemizedlist> |
---|
| 628 | </para> |
---|
| 629 | |
---|
| 630 | </sect2> |
---|
| 631 | |
---|
| 632 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 633 | <sect2 id="sect.GeneManage"> |
---|
| 634 | <title> |
---|
| 635 | General management classes |
---|
| 636 | </title> |
---|
| 637 | |
---|
| 638 | <para> |
---|
| 639 | The `global' category defines also a set of `utility' classes |
---|
| 640 | generally used within the kernel of Geant4. These classes |
---|
| 641 | include: |
---|
| 642 | |
---|
| 643 | <itemizedlist spacing="compact"> |
---|
| 644 | <listitem><para> |
---|
| 645 | <emphasis>G4Allocator</emphasis> |
---|
| 646 | <para> |
---|
| 647 | A class for fast allocation of objects to the heap through |
---|
| 648 | paging mechanism. It's meant to be used by associating it to the |
---|
| 649 | object to be allocated and defining for it <literal>new</literal> and |
---|
| 650 | <literal>delete</literal> operators via <literal>MallocSingle()</literal> and |
---|
| 651 | <literal>FreeSingle()</literal> methods of <emphasis>G4Allocator</emphasis>. |
---|
| 652 | </para> |
---|
| 653 | <para> |
---|
| 654 | <emphasis role="bold">Note</emphasis>: classes which are handled by |
---|
| 655 | <literal>G4Allocator</literal> should <emphasis>avoid</emphasis> to be used |
---|
| 656 | as base classes for others and therefore define their (eventually empty) |
---|
| 657 | destructors to be virtual (and/or inlined). Such measure is necessary in order |
---|
| 658 | to prevent bad aliasing optimisations by compilers which may potentially |
---|
| 659 | lead to crashes in the attempt to free the allocated chunks of memory. |
---|
| 660 | </para> |
---|
| 661 | <para> |
---|
| 662 | The list of allocators implicitely defined and used in Geant4 is reported here: |
---|
| 663 | <informalexample> |
---|
| 664 | <programlisting> |
---|
| 665 | - events (G4Event): anEventAllocator |
---|
| 666 | - tracks (G4Track): aTrackAllocator |
---|
| 667 | - stacked tracks (G4StackedTrack): aStackedTrackAllocator |
---|
| 668 | - primary particles (G4PrimaryParticle): aPrimaryParticleAllocator |
---|
| 669 | - primary vertices (G4PrimaryVertex): aPrimaryVertexAllocator |
---|
| 670 | - decay products (G4DecayProducts): aDecayProductsAllocator |
---|
| 671 | - digits collections of an event (G4DCofThisEvent): anDCoTHAllocator |
---|
| 672 | - digits collections (G4DigiCollection): aDCAllocator |
---|
| 673 | - hits collections of an event (G4HCofThisEvent): anHCoTHAllocator |
---|
| 674 | - hits collections (G4HitsCollection): anHCAllocator |
---|
| 675 | - trajectories (G4Trajectory): aTrajectoryAllocator |
---|
| 676 | - trajectory points (G4TrajectoryPoint): aTrajectoryPointAllocator |
---|
| 677 | - trajectory containers (G4TrajectoryContainer): aTrajectoryContainerAllocator |
---|
| 678 | - navigation levels (G4NavigationLevel): aNavigationLevelAllocator |
---|
| 679 | - navigation level nodes (G4NavigationLevelRep): aNavigLevelRepAllocator |
---|
| 680 | - reference-counted handles (G4ReferenceCountedHandle<X>): aRCHAllocator |
---|
| 681 | - counted objects (G4CountedObject<X>): aCountedObjectAllocator |
---|
| 682 | - HEPEvt primary particles (G4HEPEvtParticle): aHEPEvtParticleAllocator |
---|
| 683 | - electron occupancy objects(G4ElectronOccupancy): aElectronOccupancyAllocator |
---|
| 684 | - "rich" trajectories (G4RichTrajectory): aRichTrajectoryAllocator |
---|
| 685 | - "rich" trajectory points (G4RichTrajectoryPoint): aRichTrajectoryPointAllocator |
---|
| 686 | - "smooth" trajectories (G4SmoothTrajectory): aSmoothTrajectoryAllocator |
---|
| 687 | - "smooth" trajectory points (G4SmoothTrajectoryPoint): aSmoothTrajectoryPointAllocator |
---|
| 688 | - "ray" trajectories (G4RayTrajectory): G4RayTrajectoryAllocator |
---|
| 689 | - "ray" trajectory points (G4RayTrajectoryPoint): G4RayTrajectoryPointAllocator |
---|
| 690 | </programlisting> |
---|
| 691 | </informalexample> |
---|
| 692 | For each of these allocators, accessible from the global namespace, it is |
---|
| 693 | possible to monitor the allocation in their memory pools or force them to |
---|
| 694 | release the allocated memory (for example at the end of a run): |
---|
| 695 | <informalexample> |
---|
| 696 | <programlisting> |
---|
| 697 | // Return the size of the total memory allocated for tracks |
---|
| 698 | // |
---|
| 699 | aTrackAllocator.GetAllocatedSize(); |
---|
| 700 | |
---|
| 701 | // Return allocated storage for tracks to the free store |
---|
| 702 | // |
---|
| 703 | aTrackAllocator.ResetStorage(); |
---|
| 704 | </programlisting> |
---|
| 705 | </informalexample> |
---|
| 706 | </para> |
---|
| 707 | </para></listitem> |
---|
| 708 | <listitem><para> |
---|
| 709 | <emphasis>G4ReferenceCountedHandle</emphasis> |
---|
| 710 | <para> |
---|
| 711 | Template class acting as a smart pointer and wrapping the type |
---|
| 712 | to be counted. It performs the reference counting during the |
---|
| 713 | life-time of the counted object. |
---|
| 714 | </para> |
---|
| 715 | </para></listitem> |
---|
| 716 | <listitem><para> |
---|
| 717 | <emphasis>G4FastVector</emphasis> |
---|
| 718 | <para> |
---|
| 719 | Template class defining a vector of pointers, not performing |
---|
| 720 | boundary checking. |
---|
| 721 | </para> |
---|
| 722 | </para></listitem> |
---|
| 723 | <listitem><para> |
---|
| 724 | <emphasis>G4PhysicsVector</emphasis> |
---|
| 725 | <para> |
---|
| 726 | Defines a physics vector which has values of energy-loss, |
---|
| 727 | cross-section, and other physics values of a particle in matter in |
---|
| 728 | a given range of the energy, momentum, etc. This class serves as |
---|
| 729 | the base class for a vector having various energy scale, for |
---|
| 730 | example like 'log' (<emphasis>G4PhysicsLogVector</emphasis>) 'linear' |
---|
| 731 | (<emphasis>G4PhysicsLinearVector</emphasis>), 'free' |
---|
| 732 | (<emphasis>G4PhysicsFreeVector</emphasis>), etc. |
---|
| 733 | </para> |
---|
| 734 | </para></listitem> |
---|
| 735 | <listitem><para> |
---|
| 736 | <emphasis>G4LPhysicsFreeVector</emphasis> |
---|
| 737 | <para> |
---|
| 738 | Implements a free vector for low energy physics cross-section |
---|
| 739 | data. A subdivision method is used to find the energy|momentum |
---|
| 740 | bin. |
---|
| 741 | </para> |
---|
| 742 | </para></listitem> |
---|
| 743 | <listitem><para> |
---|
| 744 | <emphasis>G4PhysicsOrderedFreeVector</emphasis> |
---|
| 745 | <para> |
---|
| 746 | A physics ordered free vector inherits from |
---|
| 747 | <emphasis>G4PhysicsVector</emphasis>. It provides, in addition, a method |
---|
| 748 | for the user to insert energy/value pairs in sequence. Methods to retrieve |
---|
| 749 | the max and min energies and values from the vector are also |
---|
| 750 | provided. |
---|
| 751 | </para> |
---|
| 752 | </para></listitem> |
---|
| 753 | <listitem><para> |
---|
| 754 | <emphasis>G4Timer</emphasis> |
---|
| 755 | <para> |
---|
| 756 | Utility class providing methods to measure elapsed user/system |
---|
| 757 | process time. |
---|
| 758 | Uses <literal><sys/times.h></literal> and <literal><unistd.h></literal> - |
---|
| 759 | POSIX.1. |
---|
| 760 | </para> |
---|
| 761 | </para></listitem> |
---|
| 762 | <listitem><para> |
---|
| 763 | <emphasis>G4UserLimits</emphasis> |
---|
| 764 | <para> |
---|
| 765 | Class collecting methods for get and set any kind of step |
---|
| 766 | limitation allowed in Geant4. |
---|
| 767 | </para> |
---|
| 768 | </para></listitem> |
---|
| 769 | <listitem><para> |
---|
| 770 | <emphasis>G4UnitsTable</emphasis> |
---|
| 771 | <para> |
---|
| 772 | Placeholder for the system of units in Geant4. |
---|
| 773 | </para> |
---|
| 774 | </para></listitem> |
---|
| 775 | </itemizedlist> |
---|
| 776 | </para> |
---|
| 777 | |
---|
| 778 | |
---|
| 779 | </sect2> |
---|
| 780 | </sect1> |
---|