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24 // ******************************************* 21 // ********************************************************************
25 // 22 //
26 // G4ClassicalRK4 implementation <<
27 // 23 //
28 // Created: J.Apostolakis, V.Grichine - 30.01. << 24 // $Id: G4ClassicalRK4.cc,v 1.11 2003/11/05 16:31:48 japost Exp $
>> 25 // GEANT4 tag $Name: geant4-08-00 $
>> 26 //
29 // ------------------------------------------- 27 // -------------------------------------------------------------------
30 28
31 #include "G4ClassicalRK4.hh" 29 #include "G4ClassicalRK4.hh"
32 #include "G4ThreeVector.hh" 30 #include "G4ThreeVector.hh"
33 31
34 ////////////////////////////////////////////// 32 //////////////////////////////////////////////////////////////////
35 // 33 //
36 // Constructor sets the number of variables (d 34 // Constructor sets the number of variables (default = 6)
37 // << 35
38 G4ClassicalRK4:: << 36 G4ClassicalRK4::G4ClassicalRK4(G4EquationOfMotion* EqRhs, G4int numberOfVariables)
39 G4ClassicalRK4(G4EquationOfMotion* EqRhs, G4in <<
40 : G4MagErrorStepper(EqRhs, numberOfVariables 37 : G4MagErrorStepper(EqRhs, numberOfVariables)
>> 38 // fNumberOfVariables(numberOfVariables)
41 { 39 {
42 unsigned int noVariables= std::max(numberOf 40 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
43 41
44 dydxm = new G4double[noVariables]; 42 dydxm = new G4double[noVariables];
45 dydxt = new G4double[noVariables]; 43 dydxt = new G4double[noVariables];
46 yt = new G4double[noVariables]; 44 yt = new G4double[noVariables];
47 } 45 }
48 46
49 ////////////////////////////////////////////// 47 ////////////////////////////////////////////////////////////////
50 // 48 //
51 // Destructor 49 // Destructor
52 // << 50
53 G4ClassicalRK4::~G4ClassicalRK4() 51 G4ClassicalRK4::~G4ClassicalRK4()
54 { 52 {
55 delete [] dydxm; << 53 delete[] dydxm;
56 delete [] dydxt; << 54 delete[] dydxt;
57 delete [] yt; << 55 delete[] yt;
58 } 56 }
59 57
60 ////////////////////////////////////////////// 58 //////////////////////////////////////////////////////////////////////
61 // 59 //
62 // Given values for the variables y[0,..,n-1] 60 // Given values for the variables y[0,..,n-1] and their derivatives
63 // dydx[0,...,n-1] known at x, use the classic 61 // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
64 // method to advance the solution over an inte 62 // method to advance the solution over an interval h and return the
65 // incremented variables as yout[0,...,n-1], w 63 // incremented variables as yout[0,...,n-1], which not be a distinct
66 // array from y. The user supplies the routine 64 // array from y. The user supplies the routine RightHandSide(x,y,dydx),
67 // which returns derivatives dydx at x. The so 65 // which returns derivatives dydx at x. The source is routine rk4 from
68 // NRC p. 712-713 . 66 // NRC p. 712-713 .
69 // << 67
70 void 68 void
71 G4ClassicalRK4::DumbStepper( const G4double yI << 69 G4ClassicalRK4::DumbStepper( const G4double yIn[],
72 const G4double dy << 70 const G4double dydx[],
73 G4double h, << 71 G4double h,
74 G4double yO << 72 G4double yOut[])
75 { 73 {
76 const G4int nvar = GetNumberOfVariables(); << 74 const G4int nvar = this->GetNumberOfVariables(); // fNumberOfVariables();
77 G4int i; 75 G4int i;
78 G4double hh = h*0.5, h6 = h/6.0; << 76 G4double hh = h*0.5 , h6 = h/6.0 ;
79 77
80 // Initialise time to t0, needed when it is 78 // Initialise time to t0, needed when it is not updated by the integration.
81 // [ Note: Only for time dependent fi 79 // [ Note: Only for time dependent fields (usually electric)
82 // is it neccessary to inte 80 // is it neccessary to integrate the time.]
83 yt[7] = yIn[7]; 81 yt[7] = yIn[7];
84 yOut[7] = yIn[7]; 82 yOut[7] = yIn[7];
85 83
86 for(i=0; i<nvar; ++i) << 84 for(i=0;i<nvar;i++)
87 { 85 {
88 yt[i] = yIn[i] + hh*dydx[i] ; 86 yt[i] = yIn[i] + hh*dydx[i] ; // 1st Step K1=h*dydx
89 } 87 }
90 RightHandSide(yt,dydxt) ; 88 RightHandSide(yt,dydxt) ; // 2nd Step K2=h*dydxt
91 89
92 for(i=0; i<nvar; ++i) << 90 for(i=0;i<nvar;i++)
93 { 91 {
94 yt[i] = yIn[i] + hh*dydxt[i] ; 92 yt[i] = yIn[i] + hh*dydxt[i] ;
95 } 93 }
96 RightHandSide(yt,dydxm) ; 94 RightHandSide(yt,dydxm) ; // 3rd Step K3=h*dydxm
97 95
98 for(i=0; i<nvar; ++i) << 96 for(i=0;i<nvar;i++)
99 { 97 {
100 yt[i] = yIn[i] + h*dydxm[i] ; << 98 yt[i] = yIn[i] + h*dydxm[i] ;
101 dydxm[i] += dydxt[i] ; 99 dydxm[i] += dydxt[i] ; // now dydxm=(K2+K3)/h
102 } 100 }
103 RightHandSide(yt,dydxt) ; 101 RightHandSide(yt,dydxt) ; // 4th Step K4=h*dydxt
104 102
105 for(i=0; i<nvar; ++i) // Final RK4 output << 103 for(i=0;i<nvar;i++) // Final RK4 output
106 { 104 {
107 yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0* 105 yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0*dydxm[i]); //+K1/6+K4/6+(K2+K3)/3
108 } 106 }
109 if ( nvar == 12 ) { NormalisePolarizationVe << 107 // NormaliseTangentVector( yOut );
110 108
111 } // end of DumbStepper ..................... 109 } // end of DumbStepper ....................................................
112 110
113 ////////////////////////////////////////////// 111 ////////////////////////////////////////////////////////////////////
114 // 112 //
115 // StepWithEst 113 // StepWithEst
116 114
117 void 115 void
118 G4ClassicalRK4::StepWithEst( const G4double*, 116 G4ClassicalRK4::StepWithEst( const G4double*,
119 const G4double*, 117 const G4double*,
120 G4double, 118 G4double,
121 G4double*, 119 G4double*,
122 G4double&, 120 G4double&,
123 G4double&, 121 G4double&,
124 const G4double*, 122 const G4double*,
125 G4double* 123 G4double* )
126 { 124 {
127 G4Exception("G4ClassicalRK4::StepWithEst()", << 125 G4Exception("G4ClassicalRK4::StepWithEst()", "ObsoleteMethod",
128 FatalException, "Method no longe 126 FatalException, "Method no longer used.");
129 127
130 } // end of StepWithEst ..................... 128 } // end of StepWithEst ......................................................
>> 129
131 130