RK4 Class Reference

#include <ConstantStepOdeSolver.h>

Inheritance diagram for RK4:

Public Member Functions
const char *	methodName () const
	RK4 ()
	RK4 (const AbsODERHS &rhs)
Public Member Functions inherited from ConstantStepOdeSolver
	ConstantStepOdeSolver ()
	ConstantStepOdeSolver (const AbsODERHS &rhs)
	ConstantStepOdeSolver (const ConstantStepOdeSolver &r)
double	getCoordinate (const unsigned which, const unsigned idx) const
double	getIntegrated (unsigned which, unsigned idx) const
double	getPeakTime (unsigned which) const
const AbsODERHS *	getRHS () const
AbsODERHS *	getRHS ()
double	getTime (const unsigned idx) const
double	interpolateCoordinate (unsigned which, double t, bool cubic=false) const
double	interpolateIntegrated (unsigned which, double t, bool cubic=false) const
double	lastDeltaT () const
unsigned	lastDim () const
double	lastMaxT () const
unsigned	lastRunLength () const
ConstantStepOdeSolver &	operator= (const ConstantStepOdeSolver &r)
void	run (const double *initialConditions, unsigned lenConditions, double dt, unsigned nSteps)
void	setHistory (double dt, const double *data, unsigned dim, unsigned runLen)
void	setRHS (const AbsODERHS &rhs)
void	truncateCoordinate (unsigned which, double minValue, double maxValue)
void	writeHistory (std::ostream &os, double dt, bool cubic=false) const
void	writeIntegrated (std::ostream &os, unsigned which, double dt, bool cubic=false) const
virtual	~ConstantStepOdeSolver ()

Private Member Functions
void	step (double t, double dt, const double *x, unsigned lenX, double *coordIncrement) const

Private Attributes
std::vector< double >	buf_

Additional Inherited Members
Protected Attributes inherited from ConstantStepOdeSolver
AbsODERHS *	rhs_

Detailed Description

Definition at line 167 of file ConstantStepOdeSolver.h.

Constructor & Destructor Documentation

RK4::RK4 ( )

inline

Definition at line 170 of file ConstantStepOdeSolver.h.

: ConstantStepOdeSolver() {}

RK4::RK4 ( const AbsODERHS &  rhs )

inlineexplicit

Definition at line 172 of file ConstantStepOdeSolver.h.

: ConstantStepOdeSolver(rhs) {}

Member Function Documentation

const char* RK4::methodName ( ) const

inlinevirtual

Implements ConstantStepOdeSolver.

Definition at line 174 of file ConstantStepOdeSolver.h.

{return "4th order Runge-Kutta";}

void RK4::step ( double  t, double  dt, const double *  x, unsigned  lenX, double *  coordIncrement  ) const

privatevirtual

Implements ConstantStepOdeSolver.

Definition at line 373 of file ConstantStepOdeSolver.cc.

References buf_, AbsODERHS::calc(), i, and ConstantStepOdeSolver::rhs_.

{
    const double halfstep = dt/2.0;
    if (buf_.size() < 4*lenX)
        buf_.resize(4*lenX);
    double* k1x = &buf_[0];
    double* k2x = k1x + lenX;
    double* k3x = k2x + lenX;
    double* k4x = k3x + lenX;
    rhs_->calc(t, x, lenX, k1x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + halfstep*k1x[i];
    rhs_->calc(t + halfstep, coordIncrement, lenX, k2x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + halfstep*k2x[i];
    rhs_->calc(t + halfstep, coordIncrement, lenX, k3x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + dt*k3x[i];
    rhs_->calc(t + dt, coordIncrement, lenX, k4x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = dt/6.0*(k1x[i] + 2.0*(k2x[i] + k3x[i]) + k4x[i]);
}

Member Data Documentation

std::vector<double> RK4::buf_

mutableprivate

Definition at line 181 of file ConstantStepOdeSolver.h.

Referenced by step().