00001 // 00002 // ******************************************************************** 00003 // * License and Disclaimer * 00004 // * * 00005 // * The Geant4 software is copyright of the Copyright Holders of * 00006 // * the Geant4 Collaboration. It is provided under the terms and * 00007 // * conditions of the Geant4 Software License, included in the file * 00008 // * LICENSE and available at http://cern.ch/geant4/license . These * 00009 // * include a list of copyright holders. * 00010 // * * 00011 // * Neither the authors of this software system, nor their employing * 00012 // * institutes,nor the agencies providing financial support for this * 00013 // * work make any representation or warranty, express or implied, * 00014 // * regarding this software system or assume any liability for its * 00015 // * use. Please see the license in the file LICENSE and URL above * 00016 // * for the full disclaimer and the limitation of liability. * 00017 // * * 00018 // * This code implementation is the result of the scientific and * 00019 // * technical work of the GEANT4 collaboration. * 00020 // * By using, copying, modifying or distributing the software (or * 00021 // * any work based on the software) you agree to acknowledge its * 00022 // * use in resulting scientific publications, and indicate your * 00023 // * acceptance of all terms of the Geant4 Software license. * 00024 // ******************************************************************** 00025 // 00026 // 00027 // $Id: G4ImplicitEuler.cc 69786 2013-05-15 09:38:51Z gcosmo $ 00028 // 00029 // 00030 // Implicit Euler: 00031 // 00032 // x_1 = x_0 + h/2 * ( dx(t_0,x_0) + dx(t_0+h,x_0+h*dx(t_0,x_0) ) ) 00033 // 00034 // Second order solver. 00035 // Take the current derivative and add it to the current position. 00036 // Take the output and its derivative. Add the mean of both derivatives 00037 // to form the final output. 00038 // 00039 // W.Wander <wwc@mit.edu> 12/09/97 00040 // 00041 // -------------------------------------------------------------------- 00042 00043 #include "G4ImplicitEuler.hh" 00044 #include "G4ThreeVector.hh" 00045 00047 // 00048 // Constructor 00049 00050 G4ImplicitEuler::G4ImplicitEuler(G4EquationOfMotion *EqRhs, 00051 G4int numberOfVariables): 00052 G4MagErrorStepper(EqRhs, numberOfVariables) 00053 { 00054 unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1 00055 dydxTemp = new G4double[noVariables] ; 00056 yTemp = new G4double[noVariables] ; 00057 } 00058 00059 00061 // 00062 // Destructor 00063 00064 G4ImplicitEuler::~G4ImplicitEuler() 00065 { 00066 delete[] dydxTemp; 00067 delete[] yTemp; 00068 } 00069 00071 // 00072 // 00073 00074 void 00075 G4ImplicitEuler::DumbStepper( const G4double yIn[], 00076 const G4double dydx[], 00077 G4double h, 00078 G4double yOut[]) 00079 { 00080 G4int i; 00081 const G4int numberOfVariables= GetNumberOfVariables(); 00082 00083 // Initialise time to t0, needed when it is not updated by the integration. 00084 yTemp[7] = yOut[7] = yIn[7]; // Better to set it to NaN; // TODO 00085 00086 for( i = 0; i < numberOfVariables; i++ ) 00087 { 00088 yTemp[i] = yIn[i] + h*dydx[i] ; 00089 } 00090 00091 RightHandSide(yTemp,dydxTemp); 00092 00093 for( i = 0; i < numberOfVariables; i++ ) 00094 { 00095 yOut[i] = yIn[i] + 0.5 * h * ( dydx[i] + dydxTemp[i] ); 00096 } 00097 00098 return ; 00099 }