130 lines
4.7 KiB
C++
130 lines
4.7 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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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. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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//
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// $Id: G4ClassicalRK4.cc,v 1.8 2003/06/16 16:51:11 gunter Exp $
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// GEANT4 tag $Name: geant4-05-02 $
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//
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#include "G4ClassicalRK4.hh"
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#include "G4ThreeVector.hh"
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//////////////////////////////////////////////////////////////////
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//
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// Constructor sets the number of variables (default = 6)
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G4ClassicalRK4::G4ClassicalRK4(G4Mag_EqRhs *EqRhs, G4int numberOfVariables)
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: G4MagErrorStepper(EqRhs, numberOfVariables)
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// fNumberOfVariables(numberOfVariables)
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{
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unsigned int noVariables= std::max(numberOfVariables,8); // For Time .. 7+1
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dydxm = new G4double[noVariables];
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dydxt = new G4double[noVariables];
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yt = new G4double[noVariables];
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}
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////////////////////////////////////////////////////////////////
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//
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// Destructor
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G4ClassicalRK4::~G4ClassicalRK4()
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{
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delete[] dydxm;
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delete[] dydxt;
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delete[] yt;
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}
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//////////////////////////////////////////////////////////////////////
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//
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// Given values for the variables y[0,..,n-1] and their derivatives
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// dydx[0,...,n-1] known at x, use the classical 4th Runge-Kutta
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// method to advance the solution over an interval h and return the
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// incremented variables as yout[0,...,n-1], which not be a distinct
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// array from y. The user supplies the routine RightHandSide(x,y,dydx),
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// which returns derivatives dydx at x. The source is routine rk4 from
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// NRC p. 712-713 .
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void
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G4ClassicalRK4::DumbStepper( const G4double yIn[],
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const G4double dydx[],
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G4double h,
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G4double yOut[])
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{
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const G4int nvar = this->GetNumberOfVariables(); // fNumberOfVariables();
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G4int i;
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G4double hh = h*0.5 , h6 = h/6.0 ;
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// Initialise time to t0, needed when it is not updated by the integration.
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// [ Note: Only for time dependent fields (usually electric)
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// is it neccessary to integrate the time.]
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yt[7] = yIn[7];
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yOut[7] = yIn[7];
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for(i=0;i<nvar;i++)
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{
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yt[i] = yIn[i] + hh*dydx[i] ; // 1st Step K1=h*dydx
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}
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RightHandSide(yt,dydxt) ; // 2nd Step K2=h*dydxt
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for(i=0;i<nvar;i++)
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{
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yt[i] = yIn[i] + hh*dydxt[i] ;
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}
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RightHandSide(yt,dydxm) ; // 3rd Step K3=h*dydxm
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for(i=0;i<nvar;i++)
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{
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yt[i] = yIn[i] + h*dydxm[i] ;
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dydxm[i] += dydxt[i] ; // now dydxm=(K2+K3)/h
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}
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RightHandSide(yt,dydxt) ; // 4th Step K4=h*dydxt
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for(i=0;i<nvar;i++) // Final RK4 output
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{
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yOut[i] = yIn[i]+h6*(dydx[i]+dydxt[i]+2.0*dydxm[i]); //+K1/6+K4/6+(K2+K3)/3
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}
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// NormaliseTangentVector( yOut );
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return ;
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} // end of DumbStepper ....................................................
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////////////////////////////////////////////////////////////////////
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//
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//
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void
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G4ClassicalRK4::StepWithEst( const G4double*,
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const G4double*,
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G4double,
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G4double*,
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G4double&,
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G4double&,
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const G4double*,
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G4double* )
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{
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G4Exception("ERROR - G4ClassicalRK4::StepWithEst(): method no longer used.");
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return ;
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} // end of StepWithEst ......................................................
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