| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 // G4ImplicitEuler implementation
27 //
28 // Implicit Euler:
29 //
30 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) )
31 //
32 // Second order solver.
33 // Take the current derivative and add it to the current position.
34 // Take the output and its derivative. Add the mean of both derivatives
35 // to form the final output.
36 //
37 // Author: W. Wander <wwc@mit.edu>, 12.09.1997
38 // --------------------------------------------------------------------
39
40 #include "G4ImplicitEuler.hh"
41 #include "G4ThreeVector.hh"
42
43 /////////////////////////////////////////////////////////////////////////
44 //
45 // Constructor
46
47 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfMotion* EqRhs,
48 G4int numberOfVariables)
49 : G4MagErrorStepper(EqRhs, numberOfVariables)
50 {
51 unsigned int noVariables = std::max(numberOfVariables,8); // For Time .. 7+1
52 dydxTemp = new G4double[noVariables] ;
53 yTemp = new G4double[noVariables] ;
54 }
55
56
57 ////////////////////////////////////////////////////////////////////////
58 //
59 // Destructor
60 //
61 G4ImplicitEuler::~G4ImplicitEuler()
62 {
63 delete [] dydxTemp;
64 delete [] yTemp;
65 }
66
67 //////////////////////////////////////////////////////////////////////
68 //
69 // DumbStepper
70 //
71 void
72 G4ImplicitEuler::DumbStepper( const G4double yIn[],
73 const G4double dydx[],
74 G4double h,
75 G4double yOut[] )
76 {
77 const G4int numberOfVariables = GetNumberOfVariables();
78
79 // Initialise time to t0, needed when it is not updated by the integration.
80 //
81 yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO
82
83 for( G4int i = 0; i < numberOfVariables; ++i )
84 {
85 yTemp[i] = yIn[i] + h*dydx[i] ;
86 }
87
88 RightHandSide(yTemp,dydxTemp);
89
90 for( G4int i = 0; i < numberOfVariables; ++i )
91 {
92 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] );
93 }
94
95 return;
96 }
97