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26 //
27 /// \file GB06BOptnSplitAndKillByImportance.cc
28 /// \brief Implementation of the GB06BOptnSplitAndKillByImportance class
29
30 #include "GB06BOptnSplitAndKillByImportance.hh"
31
32 #include "G4BiasingProcessInterface.hh"
33 #include "G4BiasingProcessSharedData.hh"
34 #include "G4ParallelGeometriesLimiterProcess.hh"
35 #include "G4ProcessManager.hh"
36 #include "Randomize.hh"
37
38 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
39
40 GB06BOptnSplitAndKillByImportance::GB06BOptnSplitAndKillByImportance(G4String name)
41 : G4VBiasingOperation(name),
42 fParallelWorldIndex(-1),
43 fBiasingSharedData(nullptr),
44 fParticleChange(),
45 fDummyParticleChange()
46 {}
47
48 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
49
50 GB06BOptnSplitAndKillByImportance::~GB06BOptnSplitAndKillByImportance() {}
51
52 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
53
54 G4double GB06BOptnSplitAndKillByImportance::DistanceToApplyOperation(const G4Track*, G4double,
55 G4ForceCondition* condition)
56 {
57 // -- Remember the touchable history (ie geometry state) at the beginning of the step:
58 // -- Start by getting the process handling the step limitation in parallel
59 // -- geometries for the generic biasing:
60 auto biasingLimiterProcess = fBiasingSharedData->GetParallelGeometriesLimiterProcess();
61 fPreStepTouchableHistory =
62 biasingLimiterProcess
63 ->GetNavigator(fParallelWorldIndex) // -- get the navigator of the geometry...
64 ->CreateTouchableHistoryHandle(); // -- ...and collect the geometry state.
65
66 // -- We request to be "forced" : meaning GenerateBiasingFinalState(...) will be called
67 // -- anyway at the PostStepDoIt(...) stage (ie, when the track will have been moved to
68 // -- its end point position) and, there, we will have to handle the decision to
69 // -- split/kill if we are on a volume boundary, or do nothing, if we're not:
70 *condition = Forced;
71
72 // -- As we're forced, we make this returned length void:
73 return DBL_MAX;
74 }
75
76 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
77
78 G4VParticleChange*
79 GB06BOptnSplitAndKillByImportance::GenerateBiasingFinalState(const G4Track* track, const G4Step*)
80 {
81 // -- Given we used the "Forced" condition, this method is always called.
82 // -- We check the status of the step in the parallel geometry, and apply
83 // -- splitting/killing if the step has been limited by the geometry.
84
85 // -- We first check if we limit the step in the parallel geometry:
86 G4bool isLimiting =
87 fBiasingSharedData->GetParallelGeometriesLimiterProcess()->GetIsLimiting(fParallelWorldIndex);
88
89 // -- if not limiting, we leave the track unchanged:
90 if (!isLimiting) {
91 fDummyParticleChange.Initialize(*track);
92 return &fDummyParticleChange;
93 }
94
95 // -- We collect the geometry state at the end point step:
96 // -- Note this is the same call than in the DistanceToApplyOperation(...) for the
97 // -- fPreStepTouchableHistory, but the navigator has pushed the track in the next
98 // -- volume since then (even if the track is still on the boundary), and hence the
99 // -- geometry state has changed.
100 auto biasingLimiterProcess = fBiasingSharedData->GetParallelGeometriesLimiterProcess();
101 fPostStepTouchableHistory =
102 biasingLimiterProcess->GetNavigator(fParallelWorldIndex)->CreateTouchableHistoryHandle();
103
104 // -- We verify we are still in the "same" physical volume:
105 // -- remember : using a replica, we have "one" physical volume
106 // -- but representing many different placements, distinguished
107 // -- by replica number. By checking we are in the same physical
108 // -- volume, we verify the end step point has not reached the
109 // -- world volume of the parallel geometry:
110 if (fPreStepTouchableHistory->GetVolume() != fPostStepTouchableHistory->GetVolume()) {
111 // -- the track is leaving the volumes in which biasing is applied,
112 // -- we leave this track unchanged:
113 fDummyParticleChange.Initialize(*track);
114 return &fDummyParticleChange;
115 }
116
117 // -------------------------------------------------------------------------------------
118 // -- At this stage, we know we have a particle crossing a boundary between two slices,
119 // -- each of this slice has a well defined importance : we apply the biasing.
120 // -- We will split if the track is entering a volume with higher importance, and
121 // -- kill (applying Russian roulette) in the other case.
122 // -------------------------------------------------------------------------------------
123
124 // -- We start by getting the replica numbers:
125 G4int preReplicaNumber = fPreStepTouchableHistory->GetReplicaNumber();
126 G4int postReplicaNumber = fPostStepTouchableHistory->GetReplicaNumber();
127
128 // -- and get the related importance we defined in the importance map:
129 G4int preImportance = (*fImportanceMap)[preReplicaNumber];
130 G4int postImportance = (*fImportanceMap)[postReplicaNumber];
131
132 // -- Get track weight:
133 G4double initialWeight = track->GetWeight();
134
135 // -- Initialize the "particle change" (it will communicate the new track state to
136 // -- the tracking):
137 fParticleChange.Initialize(*track);
138
139 if (postImportance > preImportance) {
140 // -- We split :
141 G4int splittingFactor = postImportance / preImportance;
142
143 // Define the tracks weight:
144 G4double weightOfTrack = initialWeight / splittingFactor;
145
146 // Ask currect track weight to be changed to the new value:
147 fParticleChange.ProposeParentWeight(weightOfTrack);
148 // Now we clone this track (this is the actual splitting):
149 // we will then have the primary and clone of it, hence the
150 // splitting by a factor 2:
151 G4Track* clone = new G4Track(*track);
152 clone->SetWeight(weightOfTrack);
153 fParticleChange.AddSecondary(clone);
154 // -- Below's call added for safety & illustration : inform particle change to not
155 // -- modify the clone (ie : daughter) weight to make it that of the primary.
156 // -- Here this call is not mandatory as both tracks have same weights.
157 fParticleChange.SetSecondaryWeightByProcess(true);
158 }
159 else {
160 // -- We apply Russian roulette:
161 G4double survivingProbability = G4double(postImportance) / G4double(preImportance);
162
163 // Shoot a random number (in ]0,1[ segment):
164 G4double random = G4UniformRand();
165 if (random > survivingProbability) {
166 // We ask for the the track to be killed:
167 fParticleChange.ProposeTrackStatus(fStopAndKill);
168 }
169 else {
170 // In this case, the track survives. We change its weight
171 // to conserve weight among killed and survival tracks:
172 fParticleChange.ProposeParentWeight(initialWeight / survivingProbability);
173 }
174 }
175
176 return &fParticleChange;
177 }
178
179 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
180