133 lines
5.0 KiB
C++
133 lines
5.0 KiB
C++
//
|
|
// ********************************************************************
|
|
// * License and Disclaimer *
|
|
// * *
|
|
// * The Geant4 software is copyright of the Copyright Holders of *
|
|
// * the Geant4 Collaboration. It is provided under the terms and *
|
|
// * conditions of the Geant4 Software License, included in the file *
|
|
// * LICENSE and available at http://cern.ch/geant4/license . These *
|
|
// * include a list of copyright holders. *
|
|
// * *
|
|
// * Neither the authors of this software system, nor their employing *
|
|
// * institutes,nor the agencies providing financial support for this *
|
|
// * work make any representation or warranty, express or implied, *
|
|
// * regarding this software system or assume any liability for its *
|
|
// * use. Please see the license in the file LICENSE and URL above *
|
|
// * for the full disclaimer and the limitation of liability. *
|
|
// * *
|
|
// * This code implementation is the result of the scientific and *
|
|
// * technical work of the GEANT4 collaboration. *
|
|
// * By using, copying, modifying or distributing the software (or *
|
|
// * any work based on the software) you agree to acknowledge its *
|
|
// * use in resulting scientific publications, and indicate your *
|
|
// * acceptance of all terms of the Geant4 Software license. *
|
|
// ********************************************************************
|
|
//
|
|
//
|
|
// $Id: G4ClassicalRK4.cc,v 1.12 2006/06/29 18:23:37 gunter Exp $
|
|
// GEANT4 tag $Name: geant4-09-00 $
|
|
//
|
|
// -------------------------------------------------------------------
|
|
|
|
#include "G4ClassicalRK4.hh"
|
|
#include "G4ThreeVector.hh"
|
|
|
|
//////////////////////////////////////////////////////////////////
|
|
//
|
|
// Constructor sets the number of variables (default = 6)
|
|
|
|
G4ClassicalRK4::G4ClassicalRK4(G4EquationOfMotion* EqRhs, G4int numberOfVariables)
|
|
: G4MagErrorStepper(EqRhs, numberOfVariables)
|
|
// fNumberOfVariables(numberOfVariables)
|
|
{
|
|
unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
|
|
|
|
dydxm = new G4double[noVariables];
|
|
dydxt = new G4double[noVariables];
|
|
yt = new G4double[noVariables];
|
|
}
|
|
|
|
////////////////////////////////////////////////////////////////
|
|
//
|
|
// Destructor
|
|
|
|
G4ClassicalRK4::~G4ClassicalRK4()
|
|
{
|
|
delete[] dydxm;
|
|
delete[] dydxt;
|
|
delete[] yt;
|
|
}
|
|
|
|
//////////////////////////////////////////////////////////////////////
|
|
//
|
|
// Given values for the variables y[0,..,n-1] and their derivatives
|
|
// dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
|
|
// method to advance the solution over an interval h and return the
|
|
// incremented variables as yout[0,...,n-1], which not be a distinct
|
|
// array from y. The user supplies the routine RightHandSide(x,y,dydx),
|
|
// which returns derivatives dydx at x. The source is routine rk4 from
|
|
// NRC p. 712-713 .
|
|
|
|
void
|
|
G4ClassicalRK4::DumbStepper( const G4double yIn[],
|
|
const G4double dydx[],
|
|
G4double h,
|
|
G4double yOut[])
|
|
{
|
|
const G4int nvar = this->GetNumberOfVariables(); // fNumberOfVariables();
|
|
G4int i;
|
|
G4double hh = h*0.5 , h6 = h/6.0 ;
|
|
|
|
// Initialise time to t0, needed when it is not updated by the integration.
|
|
// [ Note: Only for time dependent fields (usually electric)
|
|
// is it neccessary to integrate the time.]
|
|
yt[7] = yIn[7];
|
|
yOut[7] = yIn[7];
|
|
|
|
for(i=0;i<nvar;i++)
|
|
{
|
|
yt[i] = yIn[i] + hh*dydx[i] ; // 1st Step K1=h*dydx
|
|
}
|
|
RightHandSide(yt,dydxt) ; // 2nd Step K2=h*dydxt
|
|
|
|
for(i=0;i<nvar;i++)
|
|
{
|
|
yt[i] = yIn[i] + hh*dydxt[i] ;
|
|
}
|
|
RightHandSide(yt,dydxm) ; // 3rd Step K3=h*dydxm
|
|
|
|
for(i=0;i<nvar;i++)
|
|
{
|
|
yt[i] = yIn[i] + h*dydxm[i] ;
|
|
dydxm[i] += dydxt[i] ; // now dydxm=(K2+K3)/h
|
|
}
|
|
RightHandSide(yt,dydxt) ; // 4th Step K4=h*dydxt
|
|
|
|
for(i=0;i<nvar;i++) // Final RK4 output
|
|
{
|
|
yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0*dydxm[i]); //+K1/6+K4/6+(K2+K3)/3
|
|
}
|
|
// NormaliseTangentVector( yOut );
|
|
|
|
} // end of DumbStepper ....................................................
|
|
|
|
////////////////////////////////////////////////////////////////////
|
|
//
|
|
// StepWithEst
|
|
|
|
void
|
|
G4ClassicalRK4::StepWithEst( const G4double*,
|
|
const G4double*,
|
|
G4double,
|
|
G4double*,
|
|
G4double&,
|
|
G4double&,
|
|
const G4double*,
|
|
G4double* )
|
|
{
|
|
G4Exception("G4ClassicalRK4::StepWithEst()", "ObsoleteMethod",
|
|
FatalException, "Method no longer used.");
|
|
|
|
} // end of StepWithEst ......................................................
|
|
|