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25 // 25 //
26 // G4ImplicitEuler implementation << 26 //
>> 27 // $Id: G4ImplicitEuler.cc 66356 2012-12-18 09:02:32Z gcosmo $
>> 28 //
27 // 29 //
28 // Implicit Euler: 30 // Implicit Euler:
29 // 31 //
30 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx 32 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
31 // 33 //
32 // Second order solver. 34 // Second order solver.
33 // Take the current derivative and add it to t 35 // Take the current derivative and add it to the current position.
34 // Take the output and its derivative. Add the 36 // Take the output and its derivative. Add the mean of both derivatives
35 // to form the final output. 37 // to form the final output.
36 // 38 //
37 // Author: W. Wander <wwc@mit.edu>, 12.09.1997 << 39 // W.Wander <wwc@mit.edu> 12/09/97
>> 40 //
38 // ------------------------------------------- 41 // --------------------------------------------------------------------
39 42
40 #include "G4ImplicitEuler.hh" 43 #include "G4ImplicitEuler.hh"
41 #include "G4ThreeVector.hh" 44 #include "G4ThreeVector.hh"
42 45
43 ////////////////////////////////////////////// 46 /////////////////////////////////////////////////////////////////////////
44 // 47 //
45 // Constructor 48 // Constructor
46 49
47 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfM << 50 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfMotion *EqRhs,
48 G4int numberO << 51 G4int numberOfVariables):
49 : G4MagErrorStepper(EqRhs, numberOfVariables << 52 G4MagErrorStepper(EqRhs, numberOfVariables)
50 { 53 {
51 unsigned int noVariables = std::max(numberOf << 54 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
52 dydxTemp = new G4double[noVariables] ; 55 dydxTemp = new G4double[noVariables] ;
53 yTemp = new G4double[noVariables] ; 56 yTemp = new G4double[noVariables] ;
54 } 57 }
55 58
56 59
57 ////////////////////////////////////////////// 60 ////////////////////////////////////////////////////////////////////////
58 // 61 //
59 // Destructor 62 // Destructor
60 // << 63
61 G4ImplicitEuler::~G4ImplicitEuler() 64 G4ImplicitEuler::~G4ImplicitEuler()
62 { 65 {
63 delete [] dydxTemp; << 66 delete[] dydxTemp;
64 delete [] yTemp; << 67 delete[] yTemp;
65 } 68 }
66 69
67 ////////////////////////////////////////////// 70 //////////////////////////////////////////////////////////////////////
68 // 71 //
69 // DumbStepper <<
70 // 72 //
>> 73
71 void 74 void
72 G4ImplicitEuler::DumbStepper( const G4double y << 75 G4ImplicitEuler::DumbStepper( const G4double yIn[],
73 const G4double d << 76 const G4double dydx[],
74 G4double h << 77 G4double h,
75 G4double y << 78 G4double yOut[])
76 { 79 {
77 const G4int numberOfVariables = GetNumberOfV << 80 G4int i;
>> 81 const G4int numberOfVariables= GetNumberOfVariables();
78 82
79 // Initialise time to t0, needed when it is 83 // Initialise time to t0, needed when it is not updated by the integration.
80 // <<
81 yTemp[7] = yOut[7] = yIn[7]; // Better to 84 yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
82 85
83 for( G4int i = 0; i < numberOfVariables; ++i << 86 for( i = 0; i < numberOfVariables; i++ )
84 { 87 {
85 yTemp[i] = yIn[i] + h*dydx[i] ; 88 yTemp[i] = yIn[i] + h*dydx[i] ;
86 } 89 }
87 90
88 RightHandSide(yTemp,dydxTemp); 91 RightHandSide(yTemp,dydxTemp);
89 92
90 for( G4int i = 0; i < numberOfVariables; ++i << 93 for( i = 0; i < numberOfVariables; i++ )
91 { 94 {
92 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + d 95 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] );
93 } 96 }
94 97
95 return; << 98 return ;
96 } 99 }
97 100