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1 // 1 //
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24 // ******************************************* 21 // ********************************************************************
25 // 22 //
26 // G4MagErrorStepper implementation <<
27 // 23 //
28 // Author: W.Wander <wwc@mit.edu>, 09.12.1997 << 24 // $Id: G4MagErrorStepper.cc,v 1.9 2001/07/11 09:59:12 gunter Exp $
29 // ------------------------------------------- << 25 // GEANT4 tag $Name: geant4-04-00 $
30 << 26 //
31 #include "G4MagErrorStepper.hh" 27 #include "G4MagErrorStepper.hh"
>> 28 #include "G4ThreeVector.hh"
32 #include "G4LineSection.hh" 29 #include "G4LineSection.hh"
33 30
34 G4MagErrorStepper::~G4MagErrorStepper() 31 G4MagErrorStepper::~G4MagErrorStepper()
35 { 32 {
36 delete [] yMiddle; << 33 delete[] yMiddle;
37 delete [] dydxMid; << 34 delete[] dydxMid;
38 delete [] yInitial; << 35 delete[] yInitial;
39 delete [] yOneStep; << 36 delete[] yOneStep;
40 } 37 }
41 38
42 void G4MagErrorStepper::Stepper( const G4doubl << 39 void
43 const G4doubl << 40 G4MagErrorStepper::Stepper( const G4double yInput[],
44 G4doubl << 41 const G4double dydx[],
45 G4doubl << 42 G4double hstep,
46 G4doubl << 43 G4double yOutput[],
>> 44 G4double yError [] )
47 { 45 {
48 const G4int nvar = GetNumberOfVariables(); << 46 const G4int nvar = this->GetNumberOfVariables() ;
49 const G4int maxvar = GetNumberOfStateVariab <<
50 47
>> 48 G4int i;
51 // correction for Richardson Extrapolation. 49 // correction for Richardson Extrapolation.
52 // <<
53 G4double correction = 1. / ( (1 << Integra 50 G4double correction = 1. / ( (1 << IntegratorOrder()) -1 );
54 51
55 // Saving yInput because yInput and yOutpu 52 // Saving yInput because yInput and yOutput can be aliases for same array
56 // << 53
57 for(G4int i=0; i<nvar; ++i) << 54 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 55
72 G4double halfStep = hstep * 0.5; 56 G4double halfStep = hstep * 0.5;
73 57
74 // Do two half steps 58 // Do two half steps
75 // << 59
76 DumbStepper (yInitial, dydx, halfStep, 60 DumbStepper (yInitial, dydx, halfStep, yMiddle);
77 RightHandSide(yMiddle, dydxMid); 61 RightHandSide(yMiddle, dydxMid);
78 DumbStepper (yMiddle, dydxMid, halfStep, y 62 DumbStepper (yMiddle, dydxMid, halfStep, yOutput);
79 63
80 // Store midpoint, chord calculation 64 // Store midpoint, chord calculation
81 // << 65
82 fMidPoint = G4ThreeVector( yMiddle[0], yMi 66 fMidPoint = G4ThreeVector( yMiddle[0], yMiddle[1], yMiddle[2]);
83 67
84 // Do a full Step 68 // Do a full Step
85 // <<
86 DumbStepper(yInitial, dydx, hstep, yOneStep 69 DumbStepper(yInitial, dydx, hstep, yOneStep);
87 for(G4int i=0; i<nvar; ++i) << 70 for(i=0;i<nvar;i++) {
88 { <<
89 yError [i] = yOutput[i] - yOneStep[i] ; 71 yError [i] = yOutput[i] - yOneStep[i] ;
90 yOutput[i] += yError[i]*correction ; << 72 yOutput[i] += yError[i]*correction ; // Provides accuracy increased
91 // Provides accuracy increased by 1 or << 73 // by 1 order via the
>> 74 // Richardson Extrapolation
92 } 75 }
93 76
94 fInitialPoint = G4ThreeVector( yInitial[0], 77 fInitialPoint = G4ThreeVector( yInitial[0], yInitial[1], yInitial[2]);
95 fFinalPoint = G4ThreeVector( yOutput[0], 78 fFinalPoint = G4ThreeVector( yOutput[0], yOutput[1], yOutput[2]);
96 79
97 return; << 80 return ;
98 } 81 }
99 82
100 G4double G4MagErrorStepper::DistChord() const << 83
>> 84
>> 85 G4double
>> 86 G4MagErrorStepper::DistChord() const
101 { 87 {
102 // Estimate the maximum distance from the cu 88 // Estimate the maximum distance from the curve to the chord
103 // 89 //
104 // We estimate this using the distance of th << 90 // We estimate this using the distance of the midpoint to
105 // chord (the line between << 91 // chord (the line between
106 // 92 //
107 // Method below is good only for angle devia << 93 // Method below is good only for angle deviations < 2 pi,
108 // This restriction should not a problem for << 94 // This restriction should not a problem for the Runge cutta methods,
109 // which generally cannot integrate accurate << 95 // which generally cannot integrate accurately for large angle deviations.
110 <<
111 G4double distLine, distChord; 96 G4double distLine, distChord;
112 97
113 if (fInitialPoint != fFinalPoint) << 98 if (fInitialPoint != fFinalPoint) {
114 { << 99 distLine= G4LineSection::Distline( fMidPoint, fInitialPoint, fFinalPoint );
115 distLine = G4LineSection::Distline(fMidPo << 100 // This is a class method that gives distance of Mid
116 // This is a class method that gives di << 101 // from the Chord between the Initial and Final points.
117 // from the Chord between the Initial a <<
118 102
119 distChord = distLine; 103 distChord = distLine;
120 } << 104 }else{
121 else <<
122 { <<
123 distChord = (fMidPoint-fInitialPoint).mag 105 distChord = (fMidPoint-fInitialPoint).mag();
124 } 106 }
125 107
126 return distChord; 108 return distChord;
127 } 109 }
>> 110
128 111