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25 //
26 // G4WeightWindowAlgorithm implementation
27 //
28 // Author: Michael Dressel (CERN), 2003
29 // ----------------------------------------------------------------------
30 #include "G4WeightWindowAlgorithm.hh"
31 #include "Randomize.hh"
32
33 G4WeightWindowAlgorithm::
34 G4WeightWindowAlgorithm(G4double upperLimitFactor,
35 G4double survivalFactor,
36 G4int maxNumberOfSplits)
37 : fUpperLimitFactor(upperLimitFactor),
38 fSurvivalFactor(survivalFactor),
39 fMaxNumberOfSplits(maxNumberOfSplits)
40 {
41 }
42
43 G4WeightWindowAlgorithm::~G4WeightWindowAlgorithm() = default;
44
45 G4Nsplit_Weight
46 G4WeightWindowAlgorithm::Calculate(G4double init_w,
47 G4double lowerWeightBound) const
48 {
49 G4double survivalWeight = lowerWeightBound * fSurvivalFactor;
50 G4double upperWeight = lowerWeightBound * fUpperLimitFactor;
51
52 // initialize return value for case weight in window
53 //
54 G4Nsplit_Weight nw;
55 nw.fN = 1;
56 nw.fW = init_w;
57
58 if (init_w > upperWeight)
59 {
60 // splitting
61 //
62 G4double temp_wi_ws = init_w/upperWeight;
63 auto split_i = static_cast<G4int>(temp_wi_ws);
64 if(split_i != temp_wi_ws) { ++split_i; }
65 G4double wi_ws = init_w/split_i;
66
67 // values in case integer mode or in csae of double
68 // mode and the lower number of splits will be diced
69 //
70 nw.fN = split_i;
71 nw.fW = wi_ws;
72
73 //TB if (wi_ws <= fMaxNumberOfSplits) {
74 //TB if (wi_ws > int_wi_ws) {
75 //TB // double mode
76 //TB G4double p2 = wi_ws - int_wi_ws;
77 //TB G4double r = G4UniformRand();
78 //TB if (r<p2) {
79 //TB nw.fN = int_wi_ws + 1;
80 //TB }
81 //TB }
82 //TB }
83 //TB else {
84 //TB // fMaxNumberOfSplits < wi_ws
85 //TB nw.fN = fMaxNumberOfSplits;
86 //TB nw.fW = init_w/fMaxNumberOfSplits;
87 //TB }
88
89 }
90 else if (init_w < lowerWeightBound) // Russian roulette
91 {
92 G4double wi_ws = init_w/survivalWeight;
93 G4double p = std::max(wi_ws,1./fMaxNumberOfSplits);
94 G4double r = G4UniformRand();
95 if (r<p)
96 {
97 nw.fW = init_w/p;
98 nw.fN = 1;
99 }
100 else
101 {
102 nw.fW = 0;
103 nw.fN = 0;
104 }
105 }
106 // else do nothing
107
108 return nw;
109 }
110
111