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25 // 22 //
26 // G4HelixExplicitEuler implementation << 23 //
>> 24 // $Id: G4HelixExplicitEuler.cc,v 1.5 2003/10/31 14:35:54 gcosmo Exp $
>> 25 // GEANT4 tag $Name: geant4-07-01 $
>> 26 //
27 // 27 //
28 // Helix Explicit Euler: x_1 = x_0 + helix(h) 28 // Helix Explicit Euler: x_1 = x_0 + helix(h)
29 // with helix(h) being a helix piece of lengt << 29 // with helix(h) being a helix piece of length h
30 // Most simple approach for solving linear di << 30 // most simple approach for solving linear differential equations.
31 // Take the current derivative and add it to 31 // Take the current derivative and add it to the current position.
32 // 32 //
33 // Author: W.Wander <wwc@mit.edu>, 12.09.1997 << 33 // W.Wander <wwc@mit.edu> 12/09/97
34 // ------------------------------------------- 34 // -------------------------------------------------------------------
35 35
36 #include "G4HelixExplicitEuler.hh" 36 #include "G4HelixExplicitEuler.hh"
37 #include "G4PhysicalConstants.hh" <<
38 #include "G4ThreeVector.hh" 37 #include "G4ThreeVector.hh"
39 38
40 G4HelixExplicitEuler::G4HelixExplicitEuler(G4M << 39 void
41 : G4MagHelicalStepper(EqRhs) << 40 G4HelixExplicitEuler::DumbStepper( const G4double yIn[],
42 { << 41 G4ThreeVector Bfld,
43 } << 42 G4double h,
44 << 43 G4double yOut[])
45 G4HelixExplicitEuler::~G4HelixExplicitEuler() <<
46 <<
47 void G4HelixExplicitEuler::Stepper( const G4do <<
48 const G4do <<
49 G4do <<
50 G4do <<
51 G4do <<
52 { 44 {
53 // Estimation of the Stepping Angle << 45 AdvanceHelix(yIn, Bfld, h, yOut);
54 // <<
55 G4ThreeVector Bfld; <<
56 MagFieldEvaluate(yInput, Bfld); <<
57 <<
58 const G4int nvar = 6 ; <<
59 G4double yTemp[8], yIn[8] ; <<
60 G4ThreeVector Bfld_midpoint; <<
61 <<
62 // Saving yInput because yInput and yOut can <<
63 // <<
64 for(G4int i=0; i<nvar; ++i) <<
65 { <<
66 yIn[i] = yInput[i]; <<
67 } <<
68 <<
69 G4double h = Step * 0.5; <<
70 <<
71 // Do full step and two half steps <<
72 // <<
73 G4double yTemp2[7]; <<
74 AdvanceHelix(yIn, Bfld, h, yTemp2,yTemp); <<
75 MagFieldEvaluate(yTemp2, Bfld_midpoint) ; <<
76 AdvanceHelix(yTemp2, Bfld_midpoint, h, yOut) <<
77 SetAngCurve(GetAngCurve() * 2); <<
78 <<
79 // Error estimation <<
80 // <<
81 for(G4int i=0; i<nvar; ++i) <<
82 { <<
83 yErr[i] = yOut[i] - yTemp[i]; <<
84 } <<
85 } <<
86 46
87 G4double G4HelixExplicitEuler::DistChord() c << 47 // NormaliseTangentVector( yOut ); // this could harm more than it helps
88 { <<
89 // Implementation : must check whether h/R > <<
90 // If( h/R < pi) use G4LineSection::DistL <<
91 // Else DistChord=R_helix <<
92 // <<
93 G4double distChord; <<
94 G4double Ang_curve=GetAngCurve(); <<
95 <<
96 <<
97 if(Ang_curve<=pi) <<
98 { <<
99 distChord=GetRadHelix()*(1-std::cos(0.5*An <<
100 } <<
101 else if(Ang_curve<twopi) <<
102 { <<
103 distChord=GetRadHelix()*(1+std::cos(0.5*(t <<
104 } <<
105 else <<
106 { <<
107 distChord=2.*GetRadHelix(); <<
108 } <<
109 <<
110 return distChord; <<
111 } <<
112 <<
113 void G4HelixExplicitEuler::DumbStepper( const <<
114 <<
115 <<
116 <<
117 { <<
118 AdvanceHelix(yIn, Bfld, h, yOut); <<
119 } 48 }
120 49