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>> 1 // This code implementation is the intellectual property of
>> 2 // the GEANT4 collaboration.
1 // 3 //
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17 // * <<
18 // * This code implementation is the result <<
19 // * technical work of the GEANT4 collaboratio <<
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21 // * any work based on the software) you ag <<
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24 // ******************************************* <<
25 // 7 //
26 // G4MagErrorStepper implementation << 8 // $Id: G4MagErrorStepper.cc,v 1.8 2000/11/01 15:15:53 gcosmo Exp $
>> 9 // GEANT4 tag $Name: geant4-03-01 $
27 // 10 //
28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 <<
29 // ------------------------------------------- <<
30 <<
31 #include "G4MagErrorStepper.hh" 11 #include "G4MagErrorStepper.hh"
>> 12 #include "G4ThreeVector.hh"
32 #include "G4LineSection.hh" 13 #include "G4LineSection.hh"
33 14
34 G4MagErrorStepper::~G4MagErrorStepper() 15 G4MagErrorStepper::~G4MagErrorStepper()
35 { 16 {
36 delete [] yMiddle; << 17 delete[] yMiddle;
37 delete [] dydxMid; << 18 delete[] dydxMid;
38 delete [] yInitial; << 19 delete[] yInitial;
39 delete [] yOneStep; << 20 delete[] yOneStep;
40 } 21 }
41 22
42 void G4MagErrorStepper::Stepper( const G4doubl << 23 void
43 const G4doubl << 24 G4MagErrorStepper::Stepper( const G4double yInput[],
44 G4doubl << 25 const G4double dydx[],
45 G4doubl << 26 G4double hstep,
46 G4doubl << 27 G4double yOutput[],
>> 28 G4double yError [] )
47 { 29 {
48 const G4int nvar = GetNumberOfVariables(); << 30 const G4int nvar = this->GetNumberOfVariables() ;
49 const G4int maxvar = GetNumberOfStateVariab <<
50 31
>> 32 G4int i;
51 // correction for Richardson Extrapolation. 33 // correction for Richardson Extrapolation.
52 // <<
53 G4double correction = 1. / ( (1 << Integra 34 G4double correction = 1. / ( (1 << IntegratorOrder()) -1 );
54 35
55 // Saving yInput because yInput and yOutpu 36 // Saving yInput because yInput and yOutput can be aliases for same array
56 // << 37
57 for(G4int i=0; i<nvar; ++i) << 38 for(i=0;i<nvar;i++) yInitial[i]=yInput[i];
58 { <<
59 yInitial[i]=yInput[i]; <<
60 } <<
61 yInitial[7] = yInput[7]; // Copy the time i <<
62 yMiddle[7] = yInput[7]; // Copy the time f <<
63 yOneStep[7] = yInput[7]; // As it contribut <<
64 // yOutput[7] = yInput[7]; // -> dumb step <<
65 <<
66 for(G4int i=nvar; i<maxvar; ++i) <<
67 { <<
68 yOutput[i]=yInput[i]; <<
69 } <<
70 // yError[7] = 0.0; <<
71 39
72 G4double halfStep = hstep * 0.5; 40 G4double halfStep = hstep * 0.5;
73 41
74 // Do two half steps 42 // Do two half steps
75 // << 43
76 DumbStepper (yInitial, dydx, halfStep, 44 DumbStepper (yInitial, dydx, halfStep, yMiddle);
77 RightHandSide(yMiddle, dydxMid); 45 RightHandSide(yMiddle, dydxMid);
78 DumbStepper (yMiddle, dydxMid, halfStep, y 46 DumbStepper (yMiddle, dydxMid, halfStep, yOutput);
79 47
80 // Store midpoint, chord calculation 48 // Store midpoint, chord calculation
81 // << 49
82 fMidPoint = G4ThreeVector( yMiddle[0], yMi 50 fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]);
83 51
84 // Do a full Step 52 // Do a full Step
85 // <<
86 DumbStepper(yInitial, dydx, hstep, yOneStep 53 DumbStepper(yInitial, dydx, hstep, yOneStep);
87 for(G4int i=0; i<nvar; ++i) << 54 for(i=0;i<nvar;i++) {
88 { <<
89 yError [i] = yOutput[i] - yOneStep[i] ; 55 yError [i] = yOutput[i] - yOneStep[i] ;
90 yOutput[i] += yError[i]*correction ; << 56 yOutput[i] += yError[i]*correction ; // Provides accuracy increased
91 // Provides accuracy increased by 1 or << 57 // by 1 order via the
>> 58 // Richardson Extrapolation
92 } 59 }
93 60
94 fInitialPoint = G4ThreeVector( yInitial[0], 61 fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]);
95 fFinalPoint = G4ThreeVector( yOutput[0], 62 fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]);
96 63
97 return; << 64 return ;
98 } 65 }
99 66
100 G4double G4MagErrorStepper::DistChord() const << 67
>> 68
>> 69 G4double
>> 70 G4MagErrorStepper::DistChord() const
101 { 71 {
102 // Estimate the maximum distance from the cu 72 // Estimate the maximum distance from the curve to the chord
103 // 73 //
104 // We estimate this using the distance of th << 74 // We estimate this using the distance of the midpoint to
105 // chord (the line between << 75 // chord (the line between
106 // 76 //
107 // Method below is good only for angle devia << 77 // Method below is good only for angle deviations < 2 pi,
108 // This restriction should not a problem for << 78 // This restriction should not a problem for the Runge cutta methods,
109 // which generally cannot integrate accurate << 79 // which generally cannot integrate accurately for large angle deviations.
110 <<
111 G4double distLine, distChord; 80 G4double distLine, distChord;
112 81
113 if (fInitialPoint != fFinalPoint) << 82 if (fInitialPoint != fFinalPoint) {
114 { << 83 distLine= G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
115 distLine = G4LineSection::Distline(fMidPo << 84 // This is a class method that gives distance of Mid
116 // This is a class method that gives di << 85 // from the Chord between the Initial and Final points.
117 // from the Chord between the Initial a <<
118 86
119 distChord = distLine; 87 distChord = distLine;
120 } << 88 }else{
121 else <<
122 { <<
123 distChord = (fMidPoint-fInitialPoint).mag 89 distChord = (fMidPoint-fInitialPoint).mag();
124 } 90 }
125 91
126 return distChord; 92 return distChord;
127 } 93 }
>> 94
128 95