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25 // 22 //
26 // G4RKG3_Stepper implementation <<
27 // 23 //
28 // Created: J.Apostolakis, V.Grichine - 30.01. << 24 // $Id: G4RKG3_Stepper.cc,v 1.7 2003/04/02 08:52:21 gcosmo Exp $
29 // ------------------------------------------- << 25 // GEANT4 tag $Name: geant4-05-02-patch-01 $
30 << 26 //
31 #include "G4RKG3_Stepper.hh" 27 #include "G4RKG3_Stepper.hh"
>> 28 #include "G4ThreeVector.hh"
32 #include "G4LineSection.hh" 29 #include "G4LineSection.hh"
33 #include "G4Mag_EqRhs.hh" <<
34 <<
35 G4RKG3_Stepper::G4RKG3_Stepper(G4Mag_EqRhs* Eq <<
36 : G4MagIntegratorStepper(EqRhs,6) <<
37 { <<
38 } <<
39 30
40 G4RKG3_Stepper::~G4RKG3_Stepper() = default; << 31 void G4RKG3_Stepper::Stepper( const G4double yInput[7],
41 << 32 const G4double dydx[7],
42 void G4RKG3_Stepper::Stepper( const G4double y << 33 G4double Step,
43 const G4double d << 34 G4double yOut[7],
44 G4double S << 35 G4double yErr[])
45 G4double y <<
46 G4double y <<
47 { 36 {
48 G4double B[3]; 37 G4double B[3];
>> 38 // G4double yderiv[6];
>> 39 // G4double alpha2, beta2;
49 G4int nvar = 6 ; 40 G4int nvar = 6 ;
50 G4double by15 = 1. / 15. ; // was 0.06666 << 41 // G4double beTemp2, beta2=0;
51 42
52 G4double yTemp[8], dydxTemp[6], yIn[8]; << 43 G4int i;
>> 44 G4double by15 = 1. / 15. ; // was 0.066666666 ;
>> 45 G4double yTemp[7], dydxTemp[6], yIn[7] ;
>> 46 // Saving yInput because yInput and yOut can be aliases for same array
>> 47 for(i=0;i<nvar;i++) yIn[i]=yInput[i];
53 48
54 // Saving yInput because yInput and yOut ca <<
55 // <<
56 for(G4int i=0; i<nvar; ++i) <<
57 { <<
58 yIn[i]=yInput[i]; <<
59 } <<
60 yIn[6] = yInput[6]; <<
61 yIn[7] = yInput[7]; <<
62 G4double h = Step * 0.5; 49 G4double h = Step * 0.5;
63 hStep = Step; <<
64 // Do two half steps <<
65 50
66 StepNoErr(yIn, dydx,h, yTemp,B) ; << 51 // Do two half steps
67 <<
68 // Store Bfld for DistChord Calculation <<
69 // <<
70 for(auto i=0; i<3; ++i) <<
71 { <<
72 BfldIn[i] = B[i]; <<
73 } <<
74 // RightHandSide(yTemp,dydxTemp) ; <<
75 52
>> 53
>> 54 // To obtain B1 ...
>> 55 // GetEquationOfMotion()->GetFieldValue(yIn,B);
>> 56 // G4RKG3_Stepper::StepWithEst(yIn, dydx, Step, yOut,alpha2, beta2, B1, B2 );
>> 57
>> 58 StepNoErr(yIn, dydx,h, yTemp,B) ;
>> 59 // RightHandSide(yTemp,dydxTemp) ;
76 GetEquationOfMotion()->EvaluateRhsGivenB(yT 60 GetEquationOfMotion()->EvaluateRhsGivenB(yTemp,B,dydxTemp) ;
77 StepNoErr(yTemp,dydxTemp,h,yOut,B); << 61 StepNoErr(yTemp,dydxTemp,h,yOut,B); // ,beTemp2) ;
78 << 62 // beta2 += beTemp2;
>> 63 // beta2 *= 0.5;
>> 64
79 // Store midpoint, chord calculation 65 // Store midpoint, chord calculation
80 66
81 fyMidPoint = G4ThreeVector(yTemp[0], yTemp << 67 fyMidPoint = G4ThreeVector( yTemp[0], yTemp[1], yTemp[2]);
82 68
83 // Do a full Step 69 // Do a full Step
84 // << 70
85 h *= 2 ; 71 h *= 2 ;
86 StepNoErr(yIn,dydx,h,yTemp,B); << 72 StepNoErr(yIn,dydx,h,yTemp,B); // ,beTemp2) ;
87 for(G4int i=0; i<nvar; ++i) << 73 for(i=0;i<nvar;i++)
88 { 74 {
89 yErr[i] = yOut[i] - yTemp[i] ; 75 yErr[i] = yOut[i] - yTemp[i] ;
90 yOut[i] += yErr[i]*by15 ; // Pr 76 yOut[i] += yErr[i]*by15 ; // Provides 5th order of accuracy
91 } 77 }
92 78
93 // Store values for DistChord method << 79 // for(i=0;i<ncomp;i++)
94 // << 80 // {
95 fyInitial = G4ThreeVector( yIn[0], yIn[1] << 81 // fyInitial[i] = yIn[i];
96 fpInitial = G4ThreeVector( yIn[3], yIn[4] << 82 // fyFinal[i] = yOut[i];
>> 83 // }
>> 84
>> 85 fyInitial = G4ThreeVector( yIn[0], yIn[1], yIn[2]);
97 fyFinal = G4ThreeVector( yOut[0], yOut[1 86 fyFinal = G4ThreeVector( yOut[0], yOut[1], yOut[2]);
>> 87 // beta2 += beTemp2 ;
>> 88 // beta2 *= 0.5 ;
>> 89 // NormaliseTangentVector( yOut ); // Deleted
>> 90 return ;
98 } 91 }
99 92
100 // ------------------------------------------- 93 // ---------------------------------------------------------------------------
101 94
102 // Integrator for RK from G3 with evaluation o 95 // Integrator for RK from G3 with evaluation of error in solution and delta
103 // geometry based on naive similarity with the 96 // geometry based on naive similarity with the case of uniform magnetic field.
104 // B1[3] is input and is the first magnetic f 97 // B1[3] is input and is the first magnetic field values
105 // B2[3] is output and is the final magnetic f 98 // B2[3] is output and is the final magnetic field values.
106 // << 99
107 void G4RKG3_Stepper::StepWithEst( const G4doub 100 void G4RKG3_Stepper::StepWithEst( const G4double*,
108 const G4doub 101 const G4double*,
109 G4doub 102 G4double,
110 G4doub 103 G4double*,
111 G4doub 104 G4double&,
112 G4doub 105 G4double&,
113 const G4doub 106 const G4double*,
114 G4doub 107 G4double* )
115 108
116 { 109 {
117 G4Exception("G4RKG3_Stepper::StepWithEst()", << 110 G4Exception(" ERROR - G4RKG3_Stepper::StepWithEst(): method no longer used.");
118 FatalException, "Method no longe << 111 return ;
119 } 112 }
120 113
121 // ------------------------------------------- 114 // -----------------------------------------------------------------
122 115
123 // Integrator RK Stepper from G3 with only two 116 // Integrator RK Stepper from G3 with only two field evaluation per Step.
124 // It is used in propagation initial Step by s 117 // It is used in propagation initial Step by small substeps after solution
125 // error and delta geometry considerations. B[ 118 // error and delta geometry considerations. B[3] is magnetic field which
126 // is passed from substep to substep. 119 // is passed from substep to substep.
127 // << 120
128 void G4RKG3_Stepper::StepNoErr(const G4double << 121 void G4RKG3_Stepper::StepNoErr(const G4double tIn[7],
129 const G4double << 122 const G4double dydx[7],
130 G4double 123 G4double Step,
131 G4double << 124 G4double tOut[7],
132 G4double << 125 G4double B[3] ) // const
133 126
134 { << 127 {
135 << 128 // Copy and edit the routine above, to delete alpha2, beta2, ...
136 // Copy and edit the routine above, to dele << 129 G4double K1[7],K2[7],K3[7],K4[7] ;
137 // << 130 G4double tTemp[7], yderiv[6] ;
138 G4double K1[7], K2[7], K3[7], K4[7]; << 131 G4int i ;
139 G4double tTemp[8]={0.0}, yderiv[6]={0.0}; << 132
140 << 133 #ifdef END_CODE_G3STEPPER
141 // Need Momentum value to give correct valu << 134 G4Exception(" G4RKG3_Stepper::StepNoErr(): method to be no longer used.");
142 // equation. Integration on unit velocity, << 135 #else
143 << 136 // GetEquationOfMotion()->EvaluateRhsReturnB(tIn,dydx,B1) ;
144 G4double mom, inverse_mom; << 137
145 const G4double c1=0.5, c2=0.125, c3=1./6.; << 138 for(i=0;i<3;i++)
146 <<
147 // Correction for momentum not a velocity <<
148 // Need the protection !!! must be not zero <<
149 // <<
150 mom = std::sqrt(tIn[3]*tIn[3]+tIn[4]*tIn[4] <<
151 inverse_mom = 1./mom; <<
152 for(auto i=0; i<3; ++i) <<
153 { 139 {
154 K1[i] = Step * dydx[i+3]*inverse_mom; << 140 K1[i] = Step * dydx[i+3];
155 tTemp[i] = tIn[i] + Step*(c1*tIn[i+3]*in << 141 tTemp[i] = tIn[i] + Step*(0.5*tIn[i+3] + 0.125*K1[i]) ;
156 tTemp[i+3] = tIn[i+3] + c1*K1[i]*mom ; << 142 tTemp[i+3] = tIn[i+3] + 0.5*K1[i] ;
157 } 143 }
158 <<
159 GetEquationOfMotion()->EvaluateRhsReturnB(t 144 GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;
160 << 145 // Calculates yderiv & returns B too!
161 for(auto i=0; i<3; ++i) << 146
>> 147 for(i=0;i<3;i++)
162 { 148 {
163 K2[i] = Step * yderiv[i+3]*inverse_mom; << 149 K2[i] = Step * yderiv[i+3];
164 tTemp[i+3] = tIn[i+3] + c1*K2[i]*mom ; << 150 tTemp[i+3] = tIn[i+3] + 0.5*K2[i] ;
165 } 151 }
166 << 152
167 // Given B, calculate yderiv ! << 153 // Given B, calculate yderiv !
168 // <<
169 GetEquationOfMotion()->EvaluateRhsGivenB(tT 154 GetEquationOfMotion()->EvaluateRhsGivenB(tTemp,B,yderiv) ;
170 << 155
171 for(auto i=0; i<3; ++i) << 156 for(i=0;i<3;i++)
172 { 157 {
173 K3[i] = Step * yderiv[i+3]*inverse_mom; << 158 K3[i] = Step * yderiv[i+3];
174 tTemp[i] = tIn[i] + Step*(tIn[i+3]*inver << 159 tTemp[i] = tIn[i] + Step*(tIn[i+3] + 0.5*K3[i]) ;
175 tTemp[i+3] = tIn[i+3] + K3[i]*mom ; << 160 tTemp[i+3] = tIn[i+3] + K3[i] ;
176 } 161 }
177 162
178 // Calculates y-deriv(atives) & returns B t << 163 // Calculates y-deriv(atives) & returns B too!
179 // <<
180 GetEquationOfMotion()->EvaluateRhsReturnB(t 164 GetEquationOfMotion()->EvaluateRhsReturnB(tTemp,yderiv,B) ;
181 165
182 for(auto i=0; i<3; ++i) // Output tr << 166 for(i=0;i<3;i++) // Output trajectory vector
183 { 167 {
184 K4[i] = Step * yderiv[i+3]*inverse_mom; << 168 K4[i] = Step * yderiv[i+3];
185 tOut[i] = tIn[i] + Step*(tIn[i+3]*invers << 169 tOut[i] = tIn[i] + Step*(tIn[i+3] + (K1[i] + K2[i] + K3[i])/6.0) ;
186 tOut[i+3] = tIn[i+3] + mom*(K1[i] + 2*K2 << 170 tOut[i+3] = tIn[i+3] + (K1[i] + 2*K2[i] + 2*K3[i] +K4[i])/6.0 ;
187 } 171 }
188 tOut[6] = tIn[6]; << 172 // NormaliseTangentVector( tOut );
189 tOut[7] = tIn[7]; << 173 #endif
>> 174
>> 175 return ;
190 } 176 }
191 177
192 // ------------------------------------------- 178 // ---------------------------------------------------------------------------
193 <<
194 G4double G4RKG3_Stepper::DistChord() const <<
195 { <<
196 // Soon: must check whether h/R > 2 pi !! <<
197 // Method below is good only for < 2 pi <<
198 179
199 G4double distChord,distLine; << 180 G4double G4RKG3_Stepper::DistChord() const
200 << 181 {
201 if (fyInitial != fyFinal) << 182 // Soon: must check whether h/R > 2 pi !!
202 { << 183 // Method below is good only for < 2 pi
203 distLine = G4LineSection::Distline(fyMid <<
204 distChord = distLine; <<
205 } <<
206 else <<
207 { <<
208 distChord = (fyMidPoint-fyInitial).mag() <<
209 } <<
210 184
211 return distChord; << 185 return G4LineSection::Distline( fyMidPoint, fyInitial, fyFinal );
>> 186 // This is a class method that gives distance of Mid
>> 187 // from the Chord between the Initial and Final points.
212 } 188 }
213 189