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G4ImplicitEuler.cc
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27 // $Id: G4ImplicitEuler.cc 66356 2012-12-18 09:02:32Z gcosmo $
28 //
29 //
30 // Implicit Euler:
31 //
32 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
33 //
34 // Second order solver.
35 // Take the current derivative and add it to the current position.
36 // Take the output and its derivative. Add the mean of both derivatives
37 // to form the final output.
38 //
39 // W.Wander <wwc@mit.edu> 12/09/97
40 //
41 // --------------------------------------------------------------------
42 
43 #include "G4ImplicitEuler.hh"
44 #include "G4ThreeVector.hh"
45 
47 //
48 // Constructor
49 
51  G4int numberOfVariables):
52 G4MagErrorStepper(EqRhs, numberOfVariables)
53 {
54  unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
55  dydxTemp = new G4double[noVariables] ;
56  yTemp = new G4double[noVariables] ;
57 }
58 
59 
61 //
62 // Destructor
63 
65 {
66  delete[] dydxTemp;
67  delete[] yTemp;
68 }
69 
71 //
72 //
73 
74 void
76  const G4double dydx[],
77  G4double h,
78  G4double yOut[])
79 {
80  G4int i;
81  const G4int numberOfVariables= GetNumberOfVariables();
82 
83  // Initialise time to t0, needed when it is not updated by the integration.
84  yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
85 
86  for( i = 0; i < numberOfVariables; i++ )
87  {
88  yTemp[i] = yIn[i] + h*dydx[i] ;
89  }
90 
92 
93  for( i = 0; i < numberOfVariables; i++ )
94  {
95  yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] );
96  }
97 
98  return ;
99 }
T max(const T t1, const T t2)
brief Return the largest of the two arguments
double G4double
Definition: G4Types.hh:76
void DumbStepper(const G4double y[], const G4double dydx[], G4double h, G4double yout[])
G4ImplicitEuler(G4EquationOfMotion *EqRhs, G4int numberOfVariables=6)
void RightHandSide(const double y[], double dydx[]) const
int G4int
Definition: G4Types.hh:78
G4double * dydxTemp
G4int GetNumberOfVariables() const