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: G4HelixImplicitEuler.cc 69786 2013-05-15 09:38:51Z gcosmo $ 00028 // 00029 // 00030 // Helix Implicit Euler: 00031 // x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0) 00032 // + helix(h,t_0+h,x_0+helix(h,t0,x0) ) ) 00033 // Second order solver. 00034 // Take the current derivative and add it to the current position. 00035 // Take the output and its derivative. Add the mean of both derivatives 00036 // to form the final output 00037 // 00038 // W.Wander <wwc@mit.edu> 12/09/97 00039 // 00040 // ------------------------------------------------------------------------- 00041 00042 #include "G4HelixImplicitEuler.hh" 00043 #include "G4ThreeVector.hh" 00044 00045 void 00046 G4HelixImplicitEuler::DumbStepper( const G4double yIn[], 00047 G4ThreeVector Bfld, 00048 G4double h, 00049 G4double yOut[]) 00050 { 00051 const G4int nvar = 6 ; 00052 G4double yTemp[6], yTemp2[6]; 00053 G4ThreeVector Bfld_endpoint; 00054 00055 G4int i; 00056 00057 // Step forward like in the explicit euler case 00058 AdvanceHelix( yIn, Bfld, h, yTemp); 00059 00060 // now obtain the new field value at the new point 00061 MagFieldEvaluate(yTemp, Bfld_endpoint); 00062 00063 // and also advance along a helix for this field value 00064 AdvanceHelix( yIn, Bfld_endpoint, h, yTemp2); 00065 00066 // we take the average 00067 for( i = 0; i < nvar; i++ ) 00068 yOut[i] = 0.5 * ( yTemp[i] + yTemp2[i] ); 00069 00070 // NormaliseTangentVector( yOut ); 00071 }