G4ModifiedMidpoint Class Reference

#include <G4ModifiedMidpoint.hh>

Public Member Functions
void	DoStep (const G4double yIn[], const G4double dydxIn[], G4double yOut[], G4double hstep) const
void	DoStep (const G4double yIn[], const G4double dydxIn[], G4double yOut[], G4double hstep, G4double yMid[], G4double derivs[][G4FieldTrack::ncompSVEC]) const
	G4ModifiedMidpoint (G4EquationOfMotion *equation, G4int nvar=6, G4int steps=2)
G4EquationOfMotion *	GetEquationOfMotion ()
G4int	GetNumberOfVariables () const
G4int	GetSteps () const
void	SetEquationOfMotion (G4EquationOfMotion *equation)
void	SetSteps (G4int steps)
	~G4ModifiedMidpoint ()=default

Private Member Functions
void	copy (G4double dst[], const G4double src[]) const

Private Attributes
G4EquationOfMotion *	fEquation = nullptr
G4int	fnvar = 0
G4int	fsteps = 0

Detailed Description

Definition at line 41 of file G4ModifiedMidpoint.hh.

Constructor & Destructor Documentation

G4ModifiedMidpoint()

G4ModifiedMidpoint::G4ModifiedMidpoint	(	G4EquationOfMotion *	equation,
		G4int	nvar = 6,
		G4int	steps = 2
	)

Definition at line 36 of file G4ModifiedMidpoint.cc.

  : fEquation(equation), fnvar(nvar), fsteps(steps)
{
  if (nvar <= 0)
  {
    G4Exception("G4ModifiedMidpoint::G4ModifiedMidpoint()",
                "GeomField0002", FatalException,
                "Invalid number of variables; must be greater than zero!");
  }
}

References FatalException, and G4Exception().

~G4ModifiedMidpoint()

G4ModifiedMidpoint::~G4ModifiedMidpoint ( )

default

Member Function Documentation

copy()

void G4ModifiedMidpoint::copy ( G4double  dst[], const G4double  src[]  ) const

private

Definition at line 157 of file G4ModifiedMidpoint.cc.

{
  std::memcpy(dst, src, sizeof(G4double) * fnvar);
}

References fnvar.

Referenced by DoStep().

DoStep() [1/2]

void G4ModifiedMidpoint::DoStep	(	const G4double	yIn[],
		const G4double	dydxIn[],
		G4double	yOut[],
		G4double	hstep
	)		const

Definition at line 48 of file G4ModifiedMidpoint.cc.

{
  G4double y0[G4FieldTrack::ncompSVEC];
  G4double y1[G4FieldTrack::ncompSVEC];
  G4double yTemp[G4FieldTrack::ncompSVEC];
  setValue(yIn, Value1D::LabTime, y0, y1, yTemp, yOut);
 
  G4double dydx[G4FieldTrack::ncompSVEC];
 
  const G4double h = hstep / fsteps;
  const G4double h2 = 2 * h;
 
  // y1 = yIn + h * dydx
  //
  for (G4int i = 0; i < fnvar; ++i)
  {
    y1[i] = yIn[i] + h * dydyIn[i];
  }
 
  fEquation->RightHandSide(y1, dydx);
 
  copy(y0, yIn);
 
  // general step
  // yTemp = y1; y1 = y0 + h2 * dydx; y0 = yTemp
  //
  for (G4int i = 1; i < fsteps; ++i)
  {
    copy(yTemp, y1);
    for (G4int j = 0; j < fnvar; ++j)
    {
      y1[j] = y0[j] + h2 * dydx[j];
    }
    copy(y0, yTemp);
 
    fEquation->RightHandSide(y1, dydx);
  }
 
  // last step
  // yOut = 0.5 * (y0 + y1 + h * dydx)
  //
  for (G4int i = 0; i < fnvar; ++i)
  {
    yOut[i] = 0.5 * (y0[i] + y1[i] + h * dydx[i]);
  }
}

References copy(), fEquation, fnvar, fsteps, G4FieldTrack::ncompSVEC, G4EquationOfMotion::RightHandSide(), and field_utils::setValue().

Referenced by G4BulirschStoer::try_step().

DoStep() [2/2]

void G4ModifiedMidpoint::DoStep	(	const G4double	yIn[],
		const G4double	dydxIn[],
		G4double	yOut[],
		G4double	hstep,
		G4double	yMid[],
		G4double	derivs[][G4FieldTrack::ncompSVEC]
	)		const

Definition at line 96 of file G4ModifiedMidpoint.cc.

{
  G4double y0[G4FieldTrack::ncompSVEC];
  G4double y1[G4FieldTrack::ncompSVEC];
  G4double yTemp[G4FieldTrack::ncompSVEC];
  setValue(yIn, Value1D::LabTime, y0, y1, yTemp, yMid, yOut);
 
  const G4double h = hstep / fsteps;
  const G4double h2 = 2 * h;
 
  // y0 = yIn
  copy(y0, yIn);
 
  // y1 = y0 + h * dydx
  for (G4int i = 0; i < fnvar; ++i)
  {
    y1[i] = y0[i] + h * dydxIn[i];
  }
 
  // result of first step already gives approximation
  // at the center of the interval
  //
  if(fsteps == 2)
  {
    copy(yMid, y1);
  }
 
  fEquation->RightHandSide(y1, derivs[0]);
 
  // general step
  // yTemp = y1; y1 = y0 + h2 * dydx; y0 = yTemp
  //
  for (G4int i = 1; i < fsteps; ++i)
  {
    copy(yTemp, y1);
    for (G4int j = 0; j < fnvar; ++j)
    {
      y1[j] = y0[j] + h2 * derivs[i-1][j];
    }
    copy(y0, yTemp);
 
    // save approximation at the center of the interval
    if(i == fsteps / 2 - 1 )
    {
      copy(yMid, y1);
    }
 
    fEquation->RightHandSide(y1, derivs[i]);
  }
 
  // last step
  // yOut = 0.5 * (y0 + y1 + h * dydx)
  //
  for (G4int i = 0; i < fnvar; ++i)
  {
    yOut[i] = 0.5 * (y0[i] + y1[i] + h * derivs[fsteps-1][i]);
  }
}

References copy(), fEquation, fnvar, fsteps, G4FieldTrack::ncompSVEC, G4EquationOfMotion::RightHandSide(), and field_utils::setValue().

GetEquationOfMotion()

G4EquationOfMotion * G4ModifiedMidpoint::GetEquationOfMotion ( )

inline

GetNumberOfVariables()

G4int G4ModifiedMidpoint::GetNumberOfVariables ( ) const

inline

GetSteps()

G4int G4ModifiedMidpoint::GetSteps ( ) const

inline

SetEquationOfMotion()

void G4ModifiedMidpoint::SetEquationOfMotion ( G4EquationOfMotion *  equation )

inline

SetSteps()

void G4ModifiedMidpoint::SetSteps ( G4int  steps )

inline

Referenced by G4BulirschStoer::try_step().

Field Documentation

fEquation

G4EquationOfMotion* G4ModifiedMidpoint::fEquation = nullptr

private

Definition at line 70 of file G4ModifiedMidpoint.hh.

Referenced by DoStep().

fnvar

G4int G4ModifiedMidpoint::fnvar = 0

private

Definition at line 71 of file G4ModifiedMidpoint.hh.

Referenced by copy(), and DoStep().

fsteps

G4int G4ModifiedMidpoint::fsteps = 0

private

Definition at line 72 of file G4ModifiedMidpoint.hh.

Referenced by DoStep().

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The documentation for this class was generated from the following files:

• source/geometry/magneticfield/include/G4ModifiedMidpoint.hh
• source/geometry/magneticfield/src/G4ModifiedMidpoint.cc