include/Geant4/G4ImplicitEuler.hh

0001 //
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0025 //
0026 // G4ImplicitEuler
0027 //
0028 // Class description:
0029 //
0030 // Implicit Euler stepper for magnetic field:
0031 //      x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
0032 //
0033 // Second order solver.
0034 // Takes the current derivative and add it to the current position.
0035 // Takes the output and its derivative. Adds the mean of both
0036 // derivatives to form the final output.
0037
0038 // Author: W. Wander <wwc@mit.edu>, 12.09.1997
0039 // -------------------------------------------------------------------
0040 #ifndef G4IMPLICITEULER_HH
0041 #define G4IMPLICITEULER_HH
0042
0043 #include "G4MagErrorStepper.hh"
0044
0045 class G4ImplicitEuler : public G4MagErrorStepper
0046 {
0047   public:
0048
0049     G4ImplicitEuler(G4EquationOfMotion* EqRhs, G4int numberOfVariables = 6);
0050    ~G4ImplicitEuler() override;
0051
0052     void  DumbStepper( const G4double y[] ,
0053                        const G4double dydx[] ,
0054                              G4double h ,
0055                              G4double yout[] ) override;
0056
0057     inline G4int IntegratorOrder() const override { return 2; }
0058
0059   private:
0060
0061     G4double* dydxTemp = nullptr;
0062     G4double* yTemp = nullptr;
0063       // Temporaries, created to avoid new/delete on every call
0064 };
0065
0066 #endif