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25 //
26 //
27 /// \file GB03BOptnSplitOrKillOnBoundary.cc
28 /// \brief Implementation of the GB03BOptnSplitOrKillOnBoundary class
29
30 #include "GB03BOptnSplitOrKillOnBoundary.hh"
31
32 #include "Randomize.hh"
33
34 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
35
36 GB03BOptnSplitOrKillOnBoundary::GB03BOptnSplitOrKillOnBoundary(G4String name)
37 : G4VBiasingOperation(name), fParticleChange(), fParticleChangeForNothing()
38 {}
39
40 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
41
42 GB03BOptnSplitOrKillOnBoundary::~GB03BOptnSplitOrKillOnBoundary() {}
43
44 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
45
46 G4double GB03BOptnSplitOrKillOnBoundary::DistanceToApplyOperation(const G4Track*, G4double,
47 G4ForceCondition* condition)
48 {
49 // -- return "infinite" distance for interaction, but asks for GenerateBiasingFinalState
50 // -- being called anyway at the end of the step, by returning the "Forced" condition
51 // -- flag.
52 *condition = Forced;
53 return DBL_MAX;
54 }
55
56 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
57
58 G4VParticleChange* GB03BOptnSplitOrKillOnBoundary::GenerateBiasingFinalState(const G4Track* track,
59 const G4Step* step)
60 {
61 // Check if step is limited by the geometry: as we attached the biasing operator
62 // to the absorber layer, this volume boundary is the one of the absorber.
63 // (check of current step # of track is inelegant, but is to fix a "feature"
64 // that a cloned track can wrongly be seen in the wrong volume, because of numerical
65 // precision issue. In this case it makes a tiny step, which should be disregarded).
66 if ((step->GetPostStepPoint()->GetStepStatus() == fGeomBoundary)
67 && (track->GetCurrentStepNumber() != 1))
68 {
69 // -- Before deciding for killing or splitting, we make decision on applying
70 // -- the technique or not:
71 G4double trial = G4UniformRand(); // -- Note: G4UniformRand() is thread-safe
72 // -- engine for random numbers
73 if (trial <= fApplyProbability) {
74 // -- Get z component of track, to see if it moves forward or backward:
75 G4double pz = track->GetMomentum().z();
76
77 if (pz > 0.0) {
78 // -------------------------------------------------
79 // Here, we are moving "forward". We do "splitting":
80 // -------------------------------------------------
81
82 // Get track weight:
83 G4double initialWeight = track->GetWeight();
84 // Define the tracks weight:
85 G4double weightOfTrack = initialWeight / fSplittingFactor;
86
87 // The "particle change" is the object to be used to communicate to
88 // the tracking the update of the primary state and/or creation
89 // secondary tracks.
90 fParticleChange.Initialize(*track);
91
92 // ask currect track weight to be changed to new value:
93 fParticleChange.ProposeParentWeight(weightOfTrack);
94
95 // Now make clones of this track (this is the actual splitting):
96 // we will then have the primary and N-1 clones of it, hence the
97 // splitting by a factor N:
98 fParticleChange.SetNumberOfSecondaries(fSplittingFactor - 1);
99 for (G4int iSplit = 1; iSplit < fSplittingFactor; iSplit++) {
100 G4Track* clone = new G4Track(*track);
101 clone->SetWeight(weightOfTrack);
102 fParticleChange.AddSecondary(clone);
103 }
104 fParticleChange.SetSecondaryWeightByProcess(true); // -- tricky
105 // -- take it as is ;) [though not necessary here, put for safety]
106
107 // this new final state is returned to the tracking;
108 return &fParticleChange;
109 }
110
111 else {
112 // --------------------------------------------------------------
113 // Here, we are moving backward. We do killing, playing a russian
114 // roulette, killing 1/fSplittingFactor of the tracks in average:
115 // --------------------------------------------------------------
116
117 // Get track weight:
118 G4double initialWeight = track->GetWeight();
119
120 // The "particle change" is the object to be used to communicate to
121 // the tracking the update of the primary state and/or creation
122 // secondary tracks.
123 fParticleChange.Initialize(*track);
124
125 // Shoot a random number (in ]0,1[ segment):
126 G4double random = G4UniformRand();
127
128 // Decide to kill, keeping 1/fSplittingFactor of tracks:
129 G4double survivingProbability = 1.0 / fSplittingFactor;
130 if (random > survivingProbability) {
131 // We ask for the the track to be killed:
132 fParticleChange.ProposeTrackStatus(fStopAndKill);
133 }
134 else {
135 // In this case, the track survives. We change its weight
136 // to conserve weight among killed and survival tracks:
137 fParticleChange.ProposeParentWeight(initialWeight * fSplittingFactor);
138 }
139
140 // this new final state is returned to the tracking;
141 return &fParticleChange;
142 }
143 } // -- end of : if ( trial > probaForApplying )
144 } // -- end of : if ( ( step->GetPostStepPoint()->GetStepStatus() ==
145 // fGeomBoundary ) ...
146
147 // Here, the step was not limited by the geometry (but certainly by a physics
148 // process). We do nothing: ie we make no change to the current track.
149 fParticleChangeForNothing.Initialize(*track);
150 return &fParticleChangeForNothing;
151 }
152
153 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
154