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1 //
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25 //
26 // Gorad (Geant4 Open-source Radiation Analysis and Design)
27 //
28 // Author : Makoto Asai (SLAC National Accelerator Laboratory)
29 //
30 // Development of Gorad is funded by NASA Johnson Space Center (JSC)
31 // under the contract NNJ15HK11B.
32 //
33 // ********************************************************************
34 //
35 // GRParallelWorldBiasingProcess.cc
36 // A process that takes care of the geometry importance biasing.
37 // This class assumes the existance of a parallel world dedicated
38 // to the geometry importance biasing and biasing parameters are
39 // associated to the region defined in that parallel world.
40 //
41 // History
42 // September 8th, 2020 : first implementation
43 //
44 // ********************************************************************
45
46 #include "G4ios.hh"
47 #include "GRParallelWorldBiasingProcess.hh"
48 #include "G4Step.hh"
49 #include "G4Track.hh"
50 #include "G4Navigator.hh"
51 #include "G4PathFinder.hh"
52 #include "G4VTouchable.hh"
53 #include "G4VPhysicalVolume.hh"
54 #include "G4ParticleChange.hh"
55 #include "G4ParticleChangeForNothing.hh"
56 #include "Randomize.hh"
57 #include "G4Region.hh"
58 #include "GRBiasingRegionInfo.hh"
59
60 GRParallelWorldBiasingProcess::
61 GRParallelWorldBiasingProcess(const G4String& processName,G4ProcessType theType)
62 :G4ParallelWorldProcess(processName,theType)
63 {
64 particleChange = new G4ParticleChange();
65 emptyParticleChange = new G4ParticleChangeForNothing();
66 }
67
68 GRParallelWorldBiasingProcess::~GRParallelWorldBiasingProcess()
69 {;}
70
71 G4VParticleChange* GRParallelWorldBiasingProcess::PostStepDoIt(
72 const G4Track& track,
73 const G4Step& step)
74 {
75 fOldGhostTouchable = fGhostPostStepPoint->GetTouchableHandle();
76 CopyStep(step);
77
78 if(fOnBoundary)
79 {
80 fNewGhostTouchable = fPathFinder->CreateTouchableHandle(fNavigatorID);
81 }
82 else
83 {
84 fNewGhostTouchable = fOldGhostTouchable;
85 }
86
87 fGhostPreStepPoint->SetTouchableHandle(fOldGhostTouchable);
88 fGhostPostStepPoint->SetTouchableHandle(fNewGhostTouchable);
89
90 if(fNewGhostTouchable->GetVolume() == nullptr)
91 {
92 // world volume boundary
93 emptyParticleChange->Initialize(track);
94 return emptyParticleChange;
95 }
96 if(fNewGhostTouchable->GetVolume() == fOldGhostTouchable->GetVolume())
97 {
98 // stayed in the same volume
99 emptyParticleChange->Initialize(track);
100 return emptyParticleChange;
101 }
102
103 G4int preStepCopyNo = fOldGhostTouchable->GetReplicaNumber();
104 G4int postStepCopyNo = fNewGhostTouchable->GetReplicaNumber();
105
106 GRBiasingRegionInfo* biasInfo = static_cast<GRBiasingRegionInfo*>
107 (fNewGhostTouchable->GetVolume()->GetLogicalVolume()->GetRegion()->GetUserInformation());
108 auto probability = biasInfo->GetProbability();
109 if(probability < 1.)
110 {
111 // skip biasing to avoid over biasing
112 G4double ran = G4UniformRand();
113 if(ran > probability)
114 {
115 emptyParticleChange->Initialize(track);
116 return emptyParticleChange;
117 }
118 }
119
120 G4double trackWeight = track.GetWeight();
121 particleChange->Initialize(track);
122
123 auto biasFactor = biasInfo->GetBiasingFactor();
124 if(biasFactor==1)
125 {
126 // not biasing
127 emptyParticleChange->Initialize(track);
128 return emptyParticleChange;
129 }
130
131 if(preStepCopyNo < postStepCopyNo)
132 {
133 // getting into more important volume, i.e. do splitting
134 trackWeight /= biasFactor;
135 particleChange->ProposeParentWeight(trackWeight);
136 for(G4int iClone=1;iClone<biasFactor;iClone++)
137 {
138 G4Track* clonedTrack = new G4Track(track);
139 clonedTrack->SetWeight(trackWeight);
140 particleChange->AddSecondary(clonedTrack);
141 }
142 particleChange->SetSecondaryWeightByProcess(true);
143 }
144 else if(preStepCopyNo > postStepCopyNo)
145 {
146 // getting into less important volume, i.e. do Russian Rouletting
147 G4double survivalRate = 1.0/biasFactor;
148 G4double ran = G4UniformRand();
149 if(ran > survivalRate)
150 {
151 // dead
152 particleChange->ProposeTrackStatus(fStopAndKill);
153 }
154 else
155 {
156 // survive
157 trackWeight *= biasFactor;
158 particleChange->ProposeParentWeight(trackWeight);
159 }
160 }
161 else
162 {
163 // This should not happen!!
164 G4ExceptionDescription ed;
165 ed << "pre step point : "<<fOldGhostTouchable->GetVolume()->GetName()<<" - copy no. "<<fOldGhostTouchable->GetReplicaNumber()<<"\n"
166 << "post step point : "<<fNewGhostTouchable->GetVolume()->GetName()<<" - copy no. "<<fNewGhostTouchable->GetReplicaNumber();
167 G4Exception("GRParallelWorldBiasingProcess::PostStepDoIt()","GoradProc0001",FatalException,ed);
168 }
169
170 return particleChange;
171 }
172
173