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25 // 25 //
26 // G4RKG3_Stepper implementation <<
27 // 26 //
28 // Created: J.Apostolakis, V.Grichine - 30.01. << 27 // $Id: G4RKG3_Stepper.cc 68055 2013-03-13 14:43:28Z gcosmo $
>> 28 //
29 // ------------------------------------------- 29 // -------------------------------------------------------------------
30 30
31 #include "G4RKG3_Stepper.hh" 31 #include "G4RKG3_Stepper.hh"
32 #include "G4LineSection.hh" 32 #include "G4LineSection.hh"
33 #include "G4Mag_EqRhs.hh" 33 #include "G4Mag_EqRhs.hh"
34 34
35 G4RKG3_Stepper::G4RKG3_Stepper(G4Mag_EqRhs* Eq << 35 G4RKG3_Stepper::G4RKG3_Stepper(G4Mag_EqRhs *EqRhs)
36 : G4MagIntegratorStepper(EqRhs,6) << 36 : G4MagIntegratorStepper(EqRhs,6), hStep(0.)
37 { 37 {
38 } 38 }
39 39
40 G4RKG3_Stepper::~G4RKG3_Stepper() = default; << 40 G4RKG3_Stepper::~G4RKG3_Stepper()
>> 41 {
>> 42 }
41 43
42 void G4RKG3_Stepper::Stepper( const G4double y << 44 void G4RKG3_Stepper::Stepper( const G4double yInput[8],
43 const G4double d << 45 const G4double dydx[6],
44 G4double S << 46 G4double Step,
45 G4double y << 47 G4double yOut[8],
46 G4double y << 48 G4double yErr[])
47 { 49 {
48 G4double B[3]; 50 G4double B[3];
49 G4int nvar = 6 ; 51 G4int nvar = 6 ;
>> 52 G4int i;
50 G4double by15 = 1. / 15. ; // was 0.06666 53 G4double by15 = 1. / 15. ; // was 0.066666666 ;
51 54
52 G4double yTemp[8], dydxTemp[6], yIn[8]; << 55 G4double yTemp[8], dydxTemp[6], yIn[8] ;
53 << 56 // Saving yInput because yInput and yOut can be aliases for same array
54 // Saving yInput because yInput and yOut ca << 57 for(i=0;i<nvar;i++) yIn[i]=yInput[i];
55 // <<
56 for(G4int i=0; i<nvar; ++i) <<
57 { <<
58 yIn[i]=yInput[i]; <<
59 } <<
60 yIn[6] = yInput[6]; 58 yIn[6] = yInput[6];
61 yIn[7] = yInput[7]; 59 yIn[7] = yInput[7];
62 G4double h = Step * 0.5; 60 G4double h = Step * 0.5;
63 hStep = Step; << 61 hStep=Step;
64 // Do two half steps << 62 // Do two half steps
65 63
66 StepNoErr(yIn, dydx,h, yTemp,B) ; 64 StepNoErr(yIn, dydx,h, yTemp,B) ;
67 65
68 // Store Bfld for DistChord Calculation << 66 //Store Bfld for DistChord Calculation
69 // << 67 for(i=0;i<3;i++)BfldIn[i]=B[i];
70 for(auto i=0; i<3; ++i) << 68
71 { << 69 // RightHandSide(yTemp,dydxTemp) ;
72 BfldIn[i] = B[i]; <<
73 } <<
74 // RightHandSide(yTemp,dydxTemp) ; <<
75 70
76 GetEquationOfMotion()->EvaluateRhsGivenB(yT 71 GetEquationOfMotion()->EvaluateRhsGivenB(yTemp,B,dydxTemp) ;
77 StepNoErr(yTemp,dydxTemp,h,yOut,B); 72 StepNoErr(yTemp,dydxTemp,h,yOut,B);
78 73
79 // Store midpoint, chord calculation 74 // Store midpoint, chord calculation
80 75
81 fyMidPoint = G4ThreeVector(yTemp[0], yTemp << 76 fyMidPoint = G4ThreeVector( yTemp[0], yTemp[1], yTemp[2]);
82 77
83 // Do a full Step 78 // Do a full Step
84 // << 79
85 h *= 2 ; 80 h *= 2 ;
86 StepNoErr(yIn,dydx,h,yTemp,B); 81 StepNoErr(yIn,dydx,h,yTemp,B);
87 for(G4int i=0; i<nvar; ++i) << 82 for(i=0;i<nvar;i++)
88 { 83 {
89 yErr[i] = yOut[i] - yTemp[i] ; 84 yErr[i] = yOut[i] - yTemp[i] ;
90 yOut[i] += yErr[i]*by15 ; // Pr 85 yOut[i] += yErr[i]*by15 ; // Provides 5th order of accuracy
91 } 86 }
92 87
93 // Store values for DistChord method << 88 //Store values for DistChord method
94 // << 89
95 fyInitial = G4ThreeVector( yIn[0], yIn[1] 90 fyInitial = G4ThreeVector( yIn[0], yIn[1], yIn[2]);
96 fpInitial = G4ThreeVector( yIn[3], yIn[4] 91 fpInitial = G4ThreeVector( yIn[3], yIn[4], yIn[5]);
97 fyFinal = G4ThreeVector( yOut[0], yOut[1 92 fyFinal = G4ThreeVector( yOut[0], yOut[1], yOut[2]);
>> 93
>> 94 // NormaliseTangentVector( yOut ); // Deleted
98 } 95 }
99 96
100 // ------------------------------------------- 97 // ---------------------------------------------------------------------------
101 98
102 // Integrator for RK from G3 with evaluation o 99 // Integrator for RK from G3 with evaluation of error in solution and delta
103 // geometry based on naive similarity with the 100 // geometry based on naive similarity with the case of uniform magnetic field.
104 // B1[3] is input and is the first magnetic f 101 // B1[3] is input and is the first magnetic field values
105 // B2[3] is output and is the final magnetic f 102 // B2[3] is output and is the final magnetic field values.
106 // << 103
107 void G4RKG3_Stepper::StepWithEst( const G4doub 104 void G4RKG3_Stepper::StepWithEst( const G4double*,
108 const G4doub 105 const G4double*,
109 G4doub 106 G4double,
110 G4doub 107 G4double*,
111 G4doub 108 G4double&,
112 G4doub 109 G4double&,
113 const G4doub 110 const G4double*,
114 G4doub 111 G4double* )
115 112
116 { 113 {
117 G4Exception("G4RKG3_Stepper::StepWithEst()", 114 G4Exception("G4RKG3_Stepper::StepWithEst()", "GeomField0001",
118 FatalException, "Method no longe 115 FatalException, "Method no longer used.");
119 } 116 }
120 117
121 // ------------------------------------------- 118 // -----------------------------------------------------------------
122 119
>> 120
123 // Integrator RK Stepper from G3 with only two 121 // Integrator RK Stepper from G3 with only two field evaluation per Step.
124 // It is used in propagation initial Step by s 122 // It is used in propagation initial Step by small substeps after solution
125 // error and delta geometry considerations. B[ 123 // error and delta geometry considerations. B[3] is magnetic field which
126 // is passed from substep to substep. 124 // is passed from substep to substep.
127 // << 125
128 void G4RKG3_Stepper::StepNoErr(const G4double 126 void G4RKG3_Stepper::StepNoErr(const G4double tIn[8],
129 const G4double 127 const G4double dydx[6],
130 G4double 128 G4double Step,
131 G4double 129 G4double tOut[8],
132 G4double << 130 G4double B[3] ) // const
133 131
134 { 132 {
135 133
136 // Copy and edit the routine above, to dele << 134 // Copy and edit the routine above, to delete alpha2, beta2, ...
137 // << 135 G4double K1[7],K2[7],K3[7],K4[7] ;
138 G4double K1[7], K2[7], K3[7], K4[7]; << 136 G4double tTemp[8], yderiv[6] ;
139 G4double tTemp[8]={0.0}, yderiv[6]={0.0}; << 137
140 << 138 // Need Momentum value to give correct values to the coefficients in equation
141 // Need Momentum value to give correct valu << 139 // Integration on unit velocity, but tIn[3,4,5] is momentum
142 // equation. Integration on unit velocity, << 140 G4double mom,inverse_mom;
143 << 141 G4int i ;
144 G4double mom, inverse_mom; << 142 const G4double c1=0.5,c2=0.125,c3=1./6.;
145 const G4double c1=0.5, c2=0.125, c3=1./6.; <<
146 143
>> 144 // GetEquationOfMotion()->EvaluateRhsReturnB(tIn,dydx,B1) ;
147 // Correction for momentum not a velocity 145 // Correction for momentum not a velocity
148 // Need the protection !!! must be not zero << 146 // Need the protection !!! must be not zero
149 // << 147 mom=std::sqrt(tIn[3]*tIn[3]+tIn[4]*tIn[4]+tIn[5]*tIn[5]);
150 mom = std::sqrt(tIn[3]*tIn[3]+tIn[4]*tIn[4] << 148 inverse_mom=1./mom;
151 inverse_mom = 1./mom; << 149 for(i=0;i<3;i++)
152 for(auto i=0; i<3; ++i) <<
153 { 150 {
154 K1[i] = Step * dydx[i+3]*inverse_mom; 151 K1[i] = Step * dydx[i+3]*inverse_mom;
155 tTemp[i] = tIn[i] + Step*(c1*tIn[i+3]*in 152 tTemp[i] = tIn[i] + Step*(c1*tIn[i+3]*inverse_mom + c2*K1[i]) ;
156 tTemp[i+3] = tIn[i+3] + c1*K1[i]*mom ; 153 tTemp[i+3] = tIn[i+3] + c1*K1[i]*mom ;
>> 154
157 } 155 }
158 156
159 GetEquationOfMotion()->EvaluateRhsReturnB(t 157 GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;
>> 158
160 159
161 for(auto i=0; i<3; ++i) << 160 for(i=0;i<3;i++)
162 { 161 {
163 K2[i] = Step * yderiv[i+3]*inverse_mom; 162 K2[i] = Step * yderiv[i+3]*inverse_mom;
164 tTemp[i+3] = tIn[i+3] + c1*K2[i]*mom ; 163 tTemp[i+3] = tIn[i+3] + c1*K2[i]*mom ;
165 } 164 }
166 165
167 // Given B, calculate yderiv ! << 166 // Given B, calculate yderiv !
168 // <<
169 GetEquationOfMotion()->EvaluateRhsGivenB(tT 167 GetEquationOfMotion()->EvaluateRhsGivenB(tTemp,B,yderiv) ;
170 168
171 for(auto i=0; i<3; ++i) << 169 for(i=0;i<3;i++)
172 { 170 {
173 K3[i] = Step * yderiv[i+3]*inverse_mom; 171 K3[i] = Step * yderiv[i+3]*inverse_mom;
174 tTemp[i] = tIn[i] + Step*(tIn[i+3]*inver 172 tTemp[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom + c1*K3[i]) ;
175 tTemp[i+3] = tIn[i+3] + K3[i]*mom ; 173 tTemp[i+3] = tIn[i+3] + K3[i]*mom ;
176 } 174 }
>> 175
177 176
178 // Calculates y-deriv(atives) & returns B t << 177 // Calculates y-deriv(atives) & returns B too!
179 // <<
180 GetEquationOfMotion()->EvaluateRhsReturnB(t 178 GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;
>> 179
181 180
182 for(auto i=0; i<3; ++i) // Output tr << 181 for(i=0;i<3;i++) // Output trajectory vector
183 { 182 {
184 K4[i] = Step * yderiv[i+3]*inverse_mom; 183 K4[i] = Step * yderiv[i+3]*inverse_mom;
185 tOut[i] = tIn[i] + Step*(tIn[i+3]*invers << 184 tOut[i] = tIn[i] + Step*(tIn[i+3]*inverse_mom+ (K1[i] + K2[i] + K3[i])*c3) ;
186 tOut[i+3] = tIn[i+3] + mom*(K1[i] + 2*K2 185 tOut[i+3] = tIn[i+3] + mom*(K1[i] + 2*K2[i] + 2*K3[i] +K4[i])*c3 ;
187 } 186 }
188 tOut[6] = tIn[6]; 187 tOut[6] = tIn[6];
189 tOut[7] = tIn[7]; 188 tOut[7] = tIn[7];
>> 189 // NormaliseTangentVector( tOut );
>> 190
>> 191
190 } 192 }
191 193
>> 194
192 // ------------------------------------------- 195 // ---------------------------------------------------------------------------
193 196
194 G4double G4RKG3_Stepper::DistChord() const << 197 G4double G4RKG3_Stepper::DistChord() const
195 { << 198 {
196 // Soon: must check whether h/R > 2 pi !! 199 // Soon: must check whether h/R > 2 pi !!
197 // Method below is good only for < 2 pi << 200 // Method below is good only for < 2 pi
198 <<
199 G4double distChord,distLine; 201 G4double distChord,distLine;
200 202
201 if (fyInitial != fyFinal) << 203 if (fyInitial != fyFinal) {
202 { << 204 distLine= G4LineSection::Distline(fyMidPoint,fyInitial,fyFinal );
203 distLine = G4LineSection::Distline(fyMid << 205
204 distChord = distLine; << 206 distChord = distLine;
205 } << 207 }else{
206 else <<
207 { <<
208 distChord = (fyMidPoint-fyInitial).mag() 208 distChord = (fyMidPoint-fyInitial).mag();
209 } 209 }
210 << 210
>> 211
211 return distChord; 212 return distChord;
212 } << 213
>> 214 }
>> 215
213 216