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25 // 22 //
26 // G4MagErrorStepper implementation <<
27 // 23 //
28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 << 24 // $Id: G4MagErrorStepper.cc,v 1.12 2003/10/31 14:35:54 gcosmo Exp $
>> 25 // GEANT4 tag $Name: geant4-06-00-patch-01 $
>> 26 //
29 // ------------------------------------------- 27 // --------------------------------------------------------------------
30 28
31 #include "G4MagErrorStepper.hh" 29 #include "G4MagErrorStepper.hh"
32 #include "G4LineSection.hh" 30 #include "G4LineSection.hh"
33 31
34 G4MagErrorStepper::~G4MagErrorStepper() 32 G4MagErrorStepper::~G4MagErrorStepper()
35 { 33 {
36 delete [] yMiddle; << 34 delete[] yMiddle;
37 delete [] dydxMid; << 35 delete[] dydxMid;
38 delete [] yInitial; << 36 delete[] yInitial;
39 delete [] yOneStep; << 37 delete[] yOneStep;
40 } 38 }
41 39
42 void G4MagErrorStepper::Stepper( const G4doubl << 40 void
43 const G4doubl << 41 G4MagErrorStepper::Stepper( const G4double yInput[],
44 G4doubl << 42 const G4double dydx[],
45 G4doubl << 43 G4double hstep,
46 G4doubl << 44 G4double yOutput[],
>> 45 G4double yError [] )
47 { 46 {
48 const G4int nvar = GetNumberOfVariables(); << 47 const G4int nvar = this->GetNumberOfVariables() ;
49 const G4int maxvar = GetNumberOfStateVariab << 48 const G4int maxvar= GetNumberOfStateVariables();
50 49
>> 50 G4int i;
51 // correction for Richardson Extrapolation. 51 // correction for Richardson Extrapolation.
52 // <<
53 G4double correction = 1. / ( (1 << Integra 52 G4double correction = 1. / ( (1 << IntegratorOrder()) -1 );
54 53
55 // Saving yInput because yInput and yOutpu 54 // Saving yInput because yInput and yOutput can be aliases for same array
56 // << 55
57 for(G4int i=0; i<nvar; ++i) << 56 for(i=0;i<nvar;i++) yInitial[i]=yInput[i];
58 { << 57 yInitial[7]= yInput[7]; // Copy the time in case ... even if not really needed
59 yInitial[i]=yInput[i]; <<
60 } <<
61 yInitial[7] = yInput[7]; // Copy the time i <<
62 yMiddle[7] = yInput[7]; // Copy the time f 58 yMiddle[7] = yInput[7]; // Copy the time from initial value
63 yOneStep[7] = yInput[7]; // As it contribut 59 yOneStep[7] = yInput[7]; // As it contributes to final value of yOutput ?
64 // yOutput[7] = yInput[7]; // -> dumb step 60 // yOutput[7] = yInput[7]; // -> dumb stepper does it too for RK4
65 << 61 for(i=nvar;i<maxvar;i++) yOutput[i]=yInput[i];
66 for(G4int i=nvar; i<maxvar; ++i) <<
67 { <<
68 yOutput[i]=yInput[i]; <<
69 } <<
70 // yError[7] = 0.0; 62 // yError[7] = 0.0;
71 63
72 G4double halfStep = hstep * 0.5; 64 G4double halfStep = hstep * 0.5;
73 65
74 // Do two half steps 66 // Do two half steps
75 // << 67
76 DumbStepper (yInitial, dydx, halfStep, 68 DumbStepper (yInitial, dydx, halfStep, yMiddle);
77 RightHandSide(yMiddle, dydxMid); 69 RightHandSide(yMiddle, dydxMid);
78 DumbStepper (yMiddle, dydxMid, halfStep, y 70 DumbStepper (yMiddle, dydxMid, halfStep, yOutput);
79 71
80 // Store midpoint, chord calculation 72 // Store midpoint, chord calculation
81 // << 73
82 fMidPoint = G4ThreeVector( yMiddle[0], yMi 74 fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]);
83 75
84 // Do a full Step 76 // Do a full Step
85 // <<
86 DumbStepper(yInitial, dydx, hstep, yOneStep 77 DumbStepper(yInitial, dydx, hstep, yOneStep);
87 for(G4int i=0; i<nvar; ++i) << 78 for(i=0;i<nvar;i++) {
88 { <<
89 yError [i] = yOutput[i] - yOneStep[i] ; 79 yError [i] = yOutput[i] - yOneStep[i] ;
90 yOutput[i] += yError[i]*correction ; << 80 yOutput[i] += yError[i]*correction ; // Provides accuracy increased
91 // Provides accuracy increased by 1 or << 81 // by 1 order via the
>> 82 // Richardson Extrapolation
92 } 83 }
93 84
94 fInitialPoint = G4ThreeVector( yInitial[0], 85 fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]);
95 fFinalPoint = G4ThreeVector( yOutput[0], 86 fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]);
96 87
97 return; << 88 return ;
98 } 89 }
99 90
100 G4double G4MagErrorStepper::DistChord() const << 91
>> 92
>> 93 G4double
>> 94 G4MagErrorStepper::DistChord() const
101 { 95 {
102 // Estimate the maximum distance from the cu 96 // Estimate the maximum distance from the curve to the chord
103 // 97 //
104 // We estimate this using the distance of th << 98 // We estimate this using the distance of the midpoint to
105 // chord (the line between << 99 // chord (the line between
106 // 100 //
107 // Method below is good only for angle devia << 101 // Method below is good only for angle deviations < 2 pi,
108 // This restriction should not a problem for << 102 // This restriction should not a problem for the Runge cutta methods,
109 // which generally cannot integrate accurate << 103 // which generally cannot integrate accurately for large angle deviations.
110 <<
111 G4double distLine, distChord; 104 G4double distLine, distChord;
112 105
113 if (fInitialPoint != fFinalPoint) << 106 if (fInitialPoint != fFinalPoint) {
114 { << 107 distLine= G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
115 distLine = G4LineSection::Distline(fMidPo << 108 // This is a class method that gives distance of Mid
116 // This is a class method that gives di << 109 // from the Chord between the Initial and Final points.
117 // from the Chord between the Initial a <<
118 110
119 distChord = distLine; 111 distChord = distLine;
120 } << 112 }else{
121 else <<
122 { <<
123 distChord = (fMidPoint-fInitialPoint).mag 113 distChord = (fMidPoint-fInitialPoint).mag();
124 } 114 }
125 115
126 return distChord; 116 return distChord;
127 } 117 }
>> 118
128 119