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24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // G4MagErrorStepper implementation 26 // G4MagErrorStepper implementation
27 // 27 //
28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997
29 // ------------------------------------------- 29 // --------------------------------------------------------------------
30 30
31 #include "G4MagErrorStepper.hh" 31 #include "G4MagErrorStepper.hh"
32 #include "G4LineSection.hh" 32 #include "G4LineSection.hh"
33 33
34 G4MagErrorStepper::~G4MagErrorStepper() 34 G4MagErrorStepper::~G4MagErrorStepper()
35 { 35 {
36 delete [] yMiddle; 36 delete [] yMiddle;
37 delete [] dydxMid; 37 delete [] dydxMid;
38 delete [] yInitial; 38 delete [] yInitial;
39 delete [] yOneStep; 39 delete [] yOneStep;
40 } 40 }
41 41
42 void G4MagErrorStepper::Stepper( const G4doubl 42 void G4MagErrorStepper::Stepper( const G4double yInput[],
43 const G4doubl 43 const G4double dydx[],
44 G4doubl 44 G4double hstep,
45 G4doubl 45 G4double yOutput[],
46 G4doubl 46 G4double yError [] )
47 { 47 {
48 const G4int nvar = GetNumberOfVariables(); 48 const G4int nvar = GetNumberOfVariables();
49 const G4int maxvar = GetNumberOfStateVariab 49 const G4int maxvar = GetNumberOfStateVariables();
50 50
51 // correction for Richardson Extrapolation. 51 // correction for Richardson Extrapolation.
52 // 52 //
53 G4double correction = 1. / ( (1 << Integra 53 G4double correction = 1. / ( (1 << IntegratorOrder()) -1 );
54 54
55 // Saving yInput because yInput and yOutpu 55 // Saving yInput because yInput and yOutput can be aliases for same array
56 // 56 //
57 for(G4int i=0; i<nvar; ++i) 57 for(G4int i=0; i<nvar; ++i)
58 { 58 {
59 yInitial[i]=yInput[i]; 59 yInitial[i]=yInput[i];
60 } 60 }
61 yInitial[7] = yInput[7]; // Copy the time i 61 yInitial[7] = yInput[7]; // Copy the time in case...even if not really needed
62 yMiddle[7] = yInput[7]; // Copy the time f 62 yMiddle[7] = yInput[7]; // Copy the time from initial value
63 yOneStep[7] = yInput[7]; // As it contribut 63 yOneStep[7] = yInput[7]; // As it contributes to final value of yOutput ?
64 // yOutput[7] = yInput[7]; // -> dumb step 64 // yOutput[7] = yInput[7]; // -> dumb stepper does it too for RK4
65 65
66 for(G4int i=nvar; i<maxvar; ++i) 66 for(G4int i=nvar; i<maxvar; ++i)
67 { 67 {
68 yOutput[i]=yInput[i]; 68 yOutput[i]=yInput[i];
69 } 69 }
70 // yError[7] = 0.0; 70 // yError[7] = 0.0;
71 71
72 G4double halfStep = hstep * 0.5; 72 G4double halfStep = hstep * 0.5;
73 73
74 // Do two half steps 74 // Do two half steps
75 // 75 //
76 DumbStepper (yInitial, dydx, halfStep, 76 DumbStepper (yInitial, dydx, halfStep, yMiddle);
77 RightHandSide(yMiddle, dydxMid); 77 RightHandSide(yMiddle, dydxMid);
78 DumbStepper (yMiddle, dydxMid, halfStep, y 78 DumbStepper (yMiddle, dydxMid, halfStep, yOutput);
79 79
80 // Store midpoint, chord calculation 80 // Store midpoint, chord calculation
81 // 81 //
82 fMidPoint = G4ThreeVector( yMiddle[0], yMi 82 fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]);
83 83
84 // Do a full Step 84 // Do a full Step
85 // 85 //
86 DumbStepper(yInitial, dydx, hstep, yOneStep 86 DumbStepper(yInitial, dydx, hstep, yOneStep);
87 for(G4int i=0; i<nvar; ++i) 87 for(G4int i=0; i<nvar; ++i)
88 { 88 {
89 yError [i] = yOutput[i] - yOneStep[i] ; 89 yError [i] = yOutput[i] - yOneStep[i] ;
90 yOutput[i] += yError[i]*correction ; 90 yOutput[i] += yError[i]*correction ;
91 // Provides accuracy increased by 1 or 91 // Provides accuracy increased by 1 order via Richardson Extrapolation
92 } 92 }
93 93
94 fInitialPoint = G4ThreeVector( yInitial[0], 94 fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]);
95 fFinalPoint = G4ThreeVector( yOutput[0], 95 fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]);
96 96
97 return; 97 return;
98 } 98 }
99 99
100 G4double G4MagErrorStepper::DistChord() const 100 G4double G4MagErrorStepper::DistChord() const
101 { 101 {
102 // Estimate the maximum distance from the cu 102 // Estimate the maximum distance from the curve to the chord
103 // 103 //
104 // We estimate this using the distance of th 104 // We estimate this using the distance of the midpoint to
105 // chord (the line between 105 // chord (the line between
106 // 106 //
107 // Method below is good only for angle devia 107 // Method below is good only for angle deviations < 2 pi,
108 // This restriction should not a problem for 108 // This restriction should not a problem for the Runge cutta methods,
109 // which generally cannot integrate accurate 109 // which generally cannot integrate accurately for large angle deviations.
110 110
111 G4double distLine, distChord; 111 G4double distLine, distChord;
112 112
113 if (fInitialPoint != fFinalPoint) 113 if (fInitialPoint != fFinalPoint)
114 { 114 {
115 distLine = G4LineSection::Distline(fMidPo 115 distLine = G4LineSection::Distline(fMidPoint, fInitialPoint, fFinalPoint);
116 // This is a class method that gives di 116 // This is a class method that gives distance of Mid
117 // from the Chord between the Initial a 117 // from the Chord between the Initial and Final points.
118 118
119 distChord = distLine; 119 distChord = distLine;
120 } 120 }
121 else 121 else
122 { 122 {
123 distChord = (fMidPoint-fInitialPoint).mag 123 distChord = (fMidPoint-fInitialPoint).mag();
124 } 124 }
125 125
126 return distChord; 126 return distChord;
127 } 127 }
128 128