Gabriele Cosmo
159 lines
5.6 KiB
C++
159 lines
5.6 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// G4BogackiShampine23 implementation
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//
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// Bogacki-Shampine - 4 - 3(2) non-FSAL implementation
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//
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// Implementation of the method proposed in the publication
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// "A 3(2) pair of Runge - Kutta formulas"
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// by P. Bogacki and L. F. Shampine,
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// Appl. Math. Lett., vol. 2, no. 4, pp. 321-325, Jan. 1989.
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//
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// The Bogacki shampine method has the following Butcher's tableau
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//
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// 0 |
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// 1/2|1/2
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// 3/4|0 3/4
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// 1 |2/9 1/3 4/9
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// -------------------
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// |2/9 1/3 4/9 0
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// |7/24 1/4 1/3 1/8
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//
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// Created: Somnath Banerjee, Google Summer of Code 2015, 20 May 2015
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// Supervision: John Apostolakis, CERN
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// --------------------------------------------------------------------
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#include "G4BogackiShampine23.hh"
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#include "G4LineSection.hh"
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#include "G4FieldUtils.hh"
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using namespace field_utils;
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G4BogackiShampine23::G4BogackiShampine23(G4EquationOfMotion* EqRhs,
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G4int integrationVariables)
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: G4MagIntegratorStepper(EqRhs, integrationVariables)
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{
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SetIntegrationOrder(3);
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SetFSAL(true);
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}
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void G4BogackiShampine23::makeStep(const G4double yInput[],
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const G4double dydx[],
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const G4double hstep,
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G4double yOutput[],
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G4double* dydxOutput,
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G4double* yError) const
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{
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G4double yTemp[G4FieldTrack::ncompSVEC];
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for(G4int i = GetNumberOfVariables(); i < GetNumberOfStateVariables(); ++i)
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{
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yOutput[i] = yTemp[i] = yInput[i];
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}
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G4double ak2[G4FieldTrack::ncompSVEC],
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ak3[G4FieldTrack::ncompSVEC];
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const G4double b21 = 0.5 ,
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b31 = 0., b32 = 3.0 / 4.0,
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b41 = 2.0 / 9.0, b42 = 1.0 / 3.0, b43 = 4.0 / 9.0;
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const G4double dc1 = b41 - 7.0 / 24.0, dc2 = b42 - 1.0 / 4.0,
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dc3 = b43 - 1.0 / 3.0, dc4 = - 1.0 / 8.0;
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// RightHandSide(yInput, dydx);
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for(G4int i = 0; i < GetNumberOfVariables(); ++i)
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{
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yTemp[i] = yInput[i] + b21 * hstep * dydx[i];
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}
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RightHandSide(yTemp, ak2);
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for(G4int i = 0; i < GetNumberOfVariables(); ++i)
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{
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yTemp[i] = yInput[i] + hstep * (b31 * dydx[i] + b32 * ak2[i]);
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}
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RightHandSide(yTemp, ak3);
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for(G4int i = 0; i < GetNumberOfVariables(); ++i)
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{
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yOutput[i] = yInput[i] + hstep * (b41*dydx[i] + b42*ak2[i] + b43*ak3[i]);
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}
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if ((dydxOutput != nullptr) && (yError != nullptr))
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{
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RightHandSide(yOutput, dydxOutput);
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for(G4int i = 0; i < GetNumberOfVariables(); ++i)
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{
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yError[i] = hstep * (dc1 * dydx[i] + dc2 * ak2[i] +
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dc3 * ak3[i] + dc4 * dydxOutput[i]);
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}
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}
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}
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void G4BogackiShampine23::Stepper(const G4double yInput[],
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const G4double dydx[],
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G4double hstep,
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G4double yOutput[],
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G4double yError[])
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{
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copy(fyIn, yInput);
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copy(fdydx, dydx);
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fhstep = hstep;
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makeStep(fyIn, fdydx, fhstep, fyOut, fdydxOut, yError);
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copy(yOutput, fyOut);
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}
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void G4BogackiShampine23::Stepper(const G4double yInput[],
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const G4double dydx[],
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G4double hstep,
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G4double yOutput[],
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G4double yError[],
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G4double dydxOutput[])
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{
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copy(fyIn, yInput);
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copy(fdydx, dydx);
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fhstep = hstep;
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makeStep(fyIn, fdydx, fhstep, fyOut, fdydxOut, yError);
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copy(yOutput, fyOut);
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copy(dydxOutput, fdydxOut);
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}
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G4double G4BogackiShampine23::DistChord() const
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{
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G4double yMid[G4FieldTrack::ncompSVEC];
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makeStep(fyIn, fdydx, fhstep / 2., yMid);
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const G4ThreeVector begin = makeVector(fyIn, Value3D::Position);
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const G4ThreeVector mid = makeVector(yMid, Value3D::Position);
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const G4ThreeVector end = makeVector(fyOut, Value3D::Position);
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return G4LineSection::Distline(mid, begin, end);
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}
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