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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 1.8 2003/06/16 16:51:11 gunter Exp $
29 // ------------------------------------------- << 25 // GEANT4 tag $Name: geant4-05-02-patch-01 $
30 << 26 //
31 #include "G4ClassicalRK4.hh" 27 #include "G4ClassicalRK4.hh"
32 #include "G4ThreeVector.hh" 28 #include "G4ThreeVector.hh"
33 29
>> 30
34 ////////////////////////////////////////////// 31 //////////////////////////////////////////////////////////////////
35 // 32 //
36 // Constructor sets the number of variables (d 33 // Constructor sets the number of variables (default = 6)
37 // << 34
38 G4ClassicalRK4:: << 35 G4ClassicalRK4::G4ClassicalRK4(G4Mag_EqRhs *EqRhs, G4int numberOfVariables)
39 G4ClassicalRK4(G4EquationOfMotion* EqRhs, G4in <<
40 : G4MagErrorStepper(EqRhs, numberOfVariables 36 : G4MagErrorStepper(EqRhs, numberOfVariables)
>> 37 // fNumberOfVariables(numberOfVariables)
41 { 38 {
42 unsigned int noVariables= std::max(numberOf 39 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
43 40
44 dydxm = new G4double[noVariables]; 41 dydxm = new G4double[noVariables];
45 dydxt = new G4double[noVariables]; 42 dydxt = new G4double[noVariables];
46 yt = new G4double[noVariables]; 43 yt = new G4double[noVariables];
47 } 44 }
48 45
49 ////////////////////////////////////////////// 46 ////////////////////////////////////////////////////////////////
50 // 47 //
51 // Destructor 48 // Destructor
52 // << 49
53 G4ClassicalRK4::~G4ClassicalRK4() 50 G4ClassicalRK4::~G4ClassicalRK4()
54 { 51 {
55 delete [] dydxm; << 52 delete[] dydxm;
56 delete [] dydxt; << 53 delete[] dydxt;
57 delete [] yt; << 54 delete[] yt;
58 } 55 }
59 56
60 ////////////////////////////////////////////// 57 //////////////////////////////////////////////////////////////////////
61 // 58 //
62 // Given values for the variables y[0,..,n-1] 59 // Given values for the variables y[0,..,n-1] and their derivatives
63 // dydx[0,...,n-1] known at x, use the classic 60 // dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
64 // method to advance the solution over an inte 61 // method to advance the solution over an interval h and return the
65 // incremented variables as yout[0,...,n-1], w 62 // incremented variables as yout[0,...,n-1], which not be a distinct
66 // array from y. The user supplies the routine 63 // array from y. The user supplies the routine RightHandSide(x,y,dydx),
67 // which returns derivatives dydx at x. The so 64 // which returns derivatives dydx at x. The source is routine rk4 from
68 // NRC p. 712-713 . 65 // NRC p. 712-713 .
69 // << 66
70 void 67 void
71 G4ClassicalRK4::DumbStepper( const G4double yI << 68 G4ClassicalRK4::DumbStepper( const G4double yIn[],
72 const G4double dy << 69 const G4double dydx[],
73 G4double h, << 70 G4double h,
74 G4double yO << 71 G4double yOut[])
75 { 72 {
76 const G4int nvar = GetNumberOfVariables(); << 73 const G4int nvar = this->GetNumberOfVariables(); // fNumberOfVariables();
77 G4int i; 74 G4int i;
78 G4double hh = h*0.5, h6 = h/6.0; << 75 G4double hh = h*0.5 , h6 = h/6.0 ;
79 76
80 // Initialise time to t0, needed when it is 77 // Initialise time to t0, needed when it is not updated by the integration.
81 // [ Note: Only for time dependent fi 78 // [ Note: Only for time dependent fields (usually electric)
82 // is it neccessary to inte 79 // is it neccessary to integrate the time.]
83 yt[7] = yIn[7]; 80 yt[7] = yIn[7];
84 yOut[7] = yIn[7]; 81 yOut[7] = yIn[7];
85 82
86 for(i=0; i<nvar; ++i) << 83 for(i=0;i<nvar;i++)
87 { 84 {
88 yt[i] = yIn[i] + hh*dydx[i] ; 85 yt[i] = yIn[i] + hh*dydx[i] ; // 1st Step K1=h*dydx
89 } 86 }
90 RightHandSide(yt,dydxt) ; 87 RightHandSide(yt,dydxt) ; // 2nd Step K2=h*dydxt
91 88
92 for(i=0; i<nvar; ++i) << 89 for(i=0;i<nvar;i++)
93 { 90 {
94 yt[i] = yIn[i] + hh*dydxt[i] ; 91 yt[i] = yIn[i] + hh*dydxt[i] ;
95 } 92 }
96 RightHandSide(yt,dydxm) ; 93 RightHandSide(yt,dydxm) ; // 3rd Step K3=h*dydxm
97 94
98 for(i=0; i<nvar; ++i) << 95 for(i=0;i<nvar;i++)
99 { 96 {
100 yt[i] = yIn[i] + h*dydxm[i] ; << 97 yt[i] = yIn[i] + h*dydxm[i] ;
101 dydxm[i] += dydxt[i] ; 98 dydxm[i] += dydxt[i] ; // now dydxm=(K2+K3)/h
102 } 99 }
103 RightHandSide(yt,dydxt) ; 100 RightHandSide(yt,dydxt) ; // 4th Step K4=h*dydxt
104 101
105 for(i=0; i<nvar; ++i) // Final RK4 output << 102 for(i=0;i<nvar;i++) // Final RK4 output
106 { 103 {
107 yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0* 104 yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0*dydxm[i]); //+K1/6+K4/6+(K2+K3)/3
108 } 105 }
109 if ( nvar == 12 ) { NormalisePolarizationVe << 106 // NormaliseTangentVector( yOut );
110 107
>> 108 return ;
111 } // end of DumbStepper ..................... 109 } // end of DumbStepper ....................................................
112 110
113 ////////////////////////////////////////////// 111 ////////////////////////////////////////////////////////////////////
114 // 112 //
115 // StepWithEst << 113 //
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()", <<
128 FatalException, "Method no longe <<
129 125
>> 126 G4Exception("ERROR - G4ClassicalRK4::StepWithEst(): method no longer used.");
>> 127
>> 128 return ;
130 } // end of StepWithEst ..................... 129 } // end of StepWithEst ......................................................
131 130