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25 // 25 //
26 // G4ImplicitEuler implementation << 26 //
>> 27 // $Id: G4ImplicitEuler.cc,v 1.9 2006-06-29 18:24:11 gunter Exp $
>> 28 // GEANT4 tag $Name: not supported by cvs2svn $
>> 29 //
27 // 30 //
28 // Implicit Euler: 31 // Implicit Euler:
29 // 32 //
30 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx 33 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
31 // 34 //
32 // Second order solver. 35 // Second order solver.
33 // Take the current derivative and add it to t 36 // Take the current derivative and add it to the current position.
34 // Take the output and its derivative. Add the 37 // Take the output and its derivative. Add the mean of both derivatives
35 // to form the final output. 38 // to form the final output.
36 // 39 //
37 // Author: W. Wander <wwc@mit.edu>, 12.09.1997 << 40 // W.Wander <wwc@mit.edu> 12/09/97
>> 41 //
38 // ------------------------------------------- 42 // --------------------------------------------------------------------
39 43
40 #include "G4ImplicitEuler.hh" 44 #include "G4ImplicitEuler.hh"
41 #include "G4ThreeVector.hh" 45 #include "G4ThreeVector.hh"
42 46
43 ////////////////////////////////////////////// 47 /////////////////////////////////////////////////////////////////////////
44 // 48 //
45 // Constructor 49 // Constructor
46 50
47 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfM << 51 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfMotion *EqRhs,
48 G4int numberO << 52 G4int numberOfVariables):
49 : G4MagErrorStepper(EqRhs, numberOfVariables << 53 G4MagErrorStepper(EqRhs, numberOfVariables)
50 { 54 {
51 unsigned int noVariables = std::max(numberOf << 55 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
52 dydxTemp = new G4double[noVariables] ; 56 dydxTemp = new G4double[noVariables] ;
53 yTemp = new G4double[noVariables] ; 57 yTemp = new G4double[noVariables] ;
54 } 58 }
55 59
56 60
57 ////////////////////////////////////////////// 61 ////////////////////////////////////////////////////////////////////////
58 // 62 //
59 // Destructor 63 // Destructor
60 // << 64
61 G4ImplicitEuler::~G4ImplicitEuler() 65 G4ImplicitEuler::~G4ImplicitEuler()
62 { 66 {
63 delete [] dydxTemp; << 67 delete[] dydxTemp;
64 delete [] yTemp; << 68 delete[] yTemp;
65 } 69 }
66 70
67 ////////////////////////////////////////////// 71 //////////////////////////////////////////////////////////////////////
68 // 72 //
69 // DumbStepper <<
70 // 73 //
>> 74
71 void 75 void
72 G4ImplicitEuler::DumbStepper( const G4double y << 76 G4ImplicitEuler::DumbStepper( const G4double yIn[],
73 const G4double d << 77 const G4double dydx[],
74 G4double h << 78 G4double h,
75 G4double y << 79 G4double yOut[])
76 { 80 {
77 const G4int numberOfVariables = GetNumberOfV << 81 G4int i;
>> 82 const G4int numberOfVariables= GetNumberOfVariables();
78 83
79 // Initialise time to t0, needed when it is 84 // Initialise time to t0, needed when it is not updated by the integration.
80 // <<
81 yTemp[7] = yOut[7] = yIn[7]; // Better to 85 yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
82 86
83 for( G4int i = 0; i < numberOfVariables; ++i << 87 for( i = 0; i < numberOfVariables; i++ )
84 { 88 {
85 yTemp[i] = yIn[i] + h*dydx[i] ; 89 yTemp[i] = yIn[i] + h*dydx[i] ;
86 } 90 }
87 91
88 RightHandSide(yTemp,dydxTemp); 92 RightHandSide(yTemp,dydxTemp);
89 93
90 for( G4int i = 0; i < numberOfVariables; ++i << 94 for( i = 0; i < numberOfVariables; i++ )
91 { 95 {
92 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + d 96 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] );
93 } 97 }
94 98
95 return; << 99 return ;
96 } 100 }
97 101