| 1 | //
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| 2 | // ********************************************************************
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| 3 | // * License and Disclaimer *
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| 4 | // * *
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of *
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and *
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| 7 | // * conditions of the Geant4 Software License, included in the file *
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These *
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| 9 | // * include a list of copyright holders. *
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| 10 | // * *
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| 11 | // * Neither the authors of this software system, nor their employing *
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| 12 | // * institutes,nor the agencies providing financial support for this *
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| 13 | // * work make any representation or warranty, express or implied, *
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| 14 | // * regarding this software system or assume any liability for its *
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| 15 | // * use. Please see the license in the file LICENSE and URL above *
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| 16 | // * for the full disclaimer and the limitation of liability. *
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| 17 | // * *
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| 18 | // * This code implementation is the result of the scientific and *
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| 19 | // * technical work of the GEANT4 collaboration. *
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| 20 | // * By using, copying, modifying or distributing the software (or *
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| 21 | // * any work based on the software) you agree to acknowledge its *
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| 22 | // * use in resulting scientific publications, and indicate your *
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| 23 | // * acceptance of all terms of the Geant4 Software license. *
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| 24 | // ********************************************************************
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| 25 | //
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| 26 | //
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| 27 | // $Id: G4HelixImplicitEuler.cc,v 1.6 2006/06/29 18:24:06 gunter Exp $
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| 28 | // GEANT4 tag $Name: geant4-09-04-beta-01 $
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| 29 | //
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| 30 | //
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| 31 | // Helix Implicit Euler:
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| 32 | // x_1 = x_0 + 1/2 * ( helix(h,t_0,x_0)
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| 33 | // + helix(h,t_0+h,x_0+helix(h,t0,x0) ) )
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| 34 | // Second order solver.
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| 35 | // Take the current derivative and add it to the current position.
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| 36 | // Take the output and its derivative. Add the mean of both derivatives
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| 37 | // to form the final output
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| 38 | //
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| 39 | // W.Wander <wwc@mit.edu> 12/09/97
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| 40 | //
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| 41 | // -------------------------------------------------------------------------
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| 42 |
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| 43 | #include "G4HelixImplicitEuler.hh"
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| 44 | #include "G4ThreeVector.hh"
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| 45 |
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| 46 | void
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| 47 | G4HelixImplicitEuler::DumbStepper( const G4double yIn[],
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| 48 | G4ThreeVector Bfld,
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| 49 | G4double h,
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| 50 | G4double yOut[])
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| 51 | {
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| 52 | const G4int nvar = 6 ;
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| 53 | G4double yTemp[6], yTemp2[6];
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| 54 | G4ThreeVector Bfld_endpoint;
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| 55 |
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| 56 | G4int i;
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| 57 |
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| 58 | // Step forward like in the explicit euler case
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| 59 | AdvanceHelix( yIn, Bfld, h, yTemp);
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| 60 |
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| 61 | // now obtain the new field value at the new point
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| 62 | MagFieldEvaluate(yTemp, Bfld_endpoint);
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| 63 |
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| 64 | // and also advance along a helix for this field value
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| 65 | AdvanceHelix( yIn, Bfld_endpoint, h, yTemp2);
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| 66 |
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| 67 | // we take the average
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| 68 | for( i = 0; i < nvar; i++ )
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| 69 | yOut[i] = 0.5 * ( yTemp[i] + yTemp2[i] );
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| 70 |
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| 71 | // NormaliseTangentVector( yOut );
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| 72 | }
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