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25 // 25 //
26 // G4HelixImplicitEuler implementation << 26 //
>> 27 // $Id: G4HelixImplicitEuler.cc,v 1.6 2006-06-29 18:24:06 gunter Exp $
>> 28 // GEANT4 tag $Name: not supported by cvs2svn $
>> 29 //
27 // 30 //
28 // Helix Implicit Euler: 31 // Helix Implicit Euler:
29 // x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0) 32 // x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0)
30 // + helix(h,t_0+h,x_ 33 // + helix(h,t_0+h,x_0+helix(h,t0,x0) ) )
31 // Second order solver. 34 // Second order solver.
32 // Take the current derivative and add it to 35 // Take the current derivative and add it to the current position.
33 // Take the output and its derivative. Add th 36 // Take the output and its derivative. Add the mean of both derivatives
34 // to form the final output 37 // to form the final output
35 // 38 //
36 // Author: W.Wander <wwc@mit.edu>, 03/11/1998 << 39 // W.Wander <wwc@mit.edu> 12/09/97
>> 40 //
37 // ------------------------------------------- 41 // -------------------------------------------------------------------------
38 42
39 #include "G4HelixImplicitEuler.hh" 43 #include "G4HelixImplicitEuler.hh"
40 #include "G4ThreeVector.hh" 44 #include "G4ThreeVector.hh"
41 45
42 G4HelixImplicitEuler::G4HelixImplicitEuler(G4M <<
43 : G4MagHelicalStepper(EqRhs) <<
44 { <<
45 } <<
46 <<
47 G4HelixImplicitEuler::~G4HelixImplicitEuler() <<
48 <<
49 void 46 void
50 G4HelixImplicitEuler::DumbStepper( const G4dou << 47 G4HelixImplicitEuler::DumbStepper( const G4double yIn[],
51 G4ThreeVect << 48 G4ThreeVector Bfld,
52 G4double << 49 G4double h,
53 G4double << 50 G4double yOut[])
54 { 51 {
55 const G4int nvar = 6 ; 52 const G4int nvar = 6 ;
56 G4double yTemp[6], yTemp2[6]; 53 G4double yTemp[6], yTemp2[6];
57 G4ThreeVector Bfld_endpoint; 54 G4ThreeVector Bfld_endpoint;
58 55
>> 56 G4int i;
>> 57
59 // Step forward like in the explicit euler c 58 // Step forward like in the explicit euler case
60 // <<
61 AdvanceHelix( yIn, Bfld, h, yTemp); 59 AdvanceHelix( yIn, Bfld, h, yTemp);
62 60
63 // now obtain the new field value at the new 61 // now obtain the new field value at the new point
64 // <<
65 MagFieldEvaluate(yTemp, Bfld_endpoint); 62 MagFieldEvaluate(yTemp, Bfld_endpoint);
66 63
67 // and also advance along a helix for this f 64 // and also advance along a helix for this field value
68 // <<
69 AdvanceHelix( yIn, Bfld_endpoint, h, yTemp2) 65 AdvanceHelix( yIn, Bfld_endpoint, h, yTemp2);
70 66
71 // we take the average << 67 // we take the average
72 // << 68 for( i = 0; i < nvar; i++ )
73 for( G4int i = 0; i < nvar; ++i ) <<
74 { <<
75 yOut[i] = 0.5 * ( yTemp[i] + yTemp2[i] ); 69 yOut[i] = 0.5 * ( yTemp[i] + yTemp2[i] );
76 } <<
77 70
78 // NormaliseTangentVector( yOut ); 71 // NormaliseTangentVector( yOut );
79 } 72 }
80 73