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G4SimpleRunge.cc
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27 // $Id: G4SimpleRunge.cc 66356 2012-12-18 09:02:32Z gcosmo $
28 //
29 // Simple Runge:
30 //
31 // x_1 = x_0 + h * ( dx( t_0+h/2, x_0 + h/2 * dx( t_0, x_0) ) )
32 //
33 // Second order solver.
34 // Takes the derivative at a position to be assumed at the middle of the
35 // Step and adds it to the current position.
36 //
37 //
38 // W.Wander <wwc@mit.edu> 12/09/97
39 // -------------------------------------------------------------------
40 
41 #include "G4SimpleRunge.hh"
42 #include "G4ThreeVector.hh"
43 
45 //
46 // Constructor
47 
49  : G4MagErrorStepper(EqRhs, numberOfVariables),
50  fNumberOfVariables(numberOfVariables)
51 {
52 
53  unsigned int noVariables= std::max(numberOfVariables,
55  // To deal with Time >= 7+1
56  dydxTemp = new G4double[noVariables] ;
57  yTemp = new G4double[noVariables] ;
58 }
59 
60 
62 //
63 // Destructor
64 
66 {
67  delete[] dydxTemp;
68  delete[] yTemp;
69 }
70 
72 //
73 //
74 
75 void
77  const G4double dydx[],
78  G4double h,
79  G4double yOut[])
80 {
81  // Initialise time to t0, needed when it is not updated by the integration.
82  yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
83 
84  G4int i;
85 
86  for( i = 0; i < fNumberOfVariables; i++ )
87  {
88  yTemp[i] = yIn[i] + 0.5 * h*dydx[i] ;
89  }
90 
92 
93  for( i = 0; i < fNumberOfVariables; i++ )
94  {
95  yOut[i] = yIn[i] + h * ( dydxTemp[i] );
96  }
97 }
T max(const T t1, const T t2)
brief Return the largest of the two arguments
G4SimpleRunge(G4EquationOfMotion *EquationRhs, G4int numberOfVariables=6)
G4double * yTemp
G4double * dydxTemp
double G4double
Definition: G4Types.hh:76
G4int GetNumberOfStateVariables() const
void RightHandSide(const double y[], double dydx[]) const
void DumbStepper(const G4double y[], const G4double dydx[], G4double h, G4double yout[])
int G4int
Definition: G4Types.hh:78
G4int fNumberOfVariables