Genfun::StepDoublingRKStepper Class Reference

#include <StepDoublingRKStepper.hh>

Inheritance diagram for Genfun::StepDoublingRKStepper:

Public Member Functions
	StepDoublingRKStepper (const ButcherTableau &tableau)
virtual	~StepDoublingRKStepper ()
virtual void	step (const RKIntegrator::RKData *data, const RKIntegrator::RKData::Data &sdata, RKIntegrator::RKData::Data &ddata, std::vector< double > &errors) const
virtual StepDoublingRKStepper *	clone () const
void	doStep (const RKIntegrator::RKData *data, const RKIntegrator::RKData::Data &s, RKIntegrator::RKData::Data &d) const
virtual unsigned int	order () const
Public Member Functions inherited from Genfun::AdaptiveRKStepper::EEStepper
virtual	~EEStepper ()
virtual void	step (const RKIntegrator::RKData *data, const RKIntegrator::RKData::Data &sdata, RKIntegrator::RKData::Data &ddata, std::vector< double > &errors) const =0
virtual EEStepper *	clone () const =0
virtual unsigned int	order () const =0

Detailed Description

Definition at line 11 of file StepDoublingRKStepper.hh.

Constructor & Destructor Documentation

StepDoublingRKStepper()

Genfun::StepDoublingRKStepper::StepDoublingRKStepper

(

const ButcherTableau &

tableau

)

Definition at line 8 of file StepDoublingRKStepper.cc.

                                                                             :tableau(xtableau) {
  }

~StepDoublingRKStepper()

Genfun::StepDoublingRKStepper::~StepDoublingRKStepper ( )

virtual

Definition at line 11 of file StepDoublingRKStepper.cc.

                                                {
  }

Member Function Documentation

clone()

StepDoublingRKStepper * Genfun::StepDoublingRKStepper::clone ( ) const

virtual

Implements Genfun::AdaptiveRKStepper::EEStepper.

Definition at line 73 of file StepDoublingRKStepper.cc.

                                                            {
    return new StepDoublingRKStepper(*this);
  }

doStep()

void Genfun::StepDoublingRKStepper::doStep	(	const RKIntegrator::RKData *	data,
		const RKIntegrator::RKData::Data &	s,
		RKIntegrator::RKData::Data &	d
	)		const

Definition at line 38 of file StepDoublingRKStepper.cc.

                                                             {
    // First step:
    double h = (d.time - s.time);
    
    
    if (h<=0) throw std::runtime_error ("SimpleRKStepper:  negative stepsize");
    const unsigned int nvar = (unsigned int)s.variable.size();
    // Compute all of the k's..:
    //
    std::vector<std::vector<double> >k(tableau.nSteps());
    for (unsigned int i=0;i<tableau.nSteps();i++) {
      k[i].resize(nvar,0);
      Argument arg(nvar);
      for (unsigned int v=0;v<nvar;v++) arg[v]=s.variable[v];
      for (unsigned int j=0;j<i;j++) {
    for (unsigned int v=0;v<nvar;v++) arg[v] += h*tableau.A(i,j)*k[j][v];
      }
      for (unsigned int v=0;v<nvar;v++) k[i][v]=(*data->_diffEqn[v])(arg);
    }
    //
    // Final result.
    //
    for (unsigned int v=0;v<nvar;v++) d.firstDerivative[v] = 0;
    for (unsigned int i=0;i<tableau.nSteps();i++) {
      for (unsigned int v=0;v<nvar;v++) d.firstDerivative[v] += tableau.b(i)*k[i][v];
    }
    for (unsigned int v=0;v<nvar;v++)   d.variable[v] =s.variable[v]+h*d.firstDerivative[v];
                         
  }

Referenced by step().

order()

unsigned int Genfun::StepDoublingRKStepper::order ( ) const

virtual

Implements Genfun::AdaptiveRKStepper::EEStepper.

Definition at line 77 of file StepDoublingRKStepper.cc.

                                                  {
    return tableau.order();
  }

step()

void Genfun::StepDoublingRKStepper::step ( const RKIntegrator::RKData *  data, const RKIntegrator::RKData::Data &  sdata, RKIntegrator::RKData::Data &  ddata, std::vector< double > &  errors  ) const

virtual

Implements Genfun::AdaptiveRKStepper::EEStepper.

Definition at line 14 of file StepDoublingRKStepper.cc.

                                                                     {
    const unsigned int nvar = (unsigned int)s.variable.size();
    RKIntegrator::RKData::Data d1(nvar),d2(nvar);
 
    doStep(data,s,d);
    double dt = (d.time - s.time);
    d1.time = s.time + dt/2.0;
    d2.time = d.time;
 
    doStep(data, s,d1);
    doStep(data,d1,d2);
 
    // Error estimate:
    errors.resize(nvar);
    for (size_t v=0;v<nvar;v++) errors[v]=fabs(d2.variable[v]-d.variable[v]);
 
    // Final correction:
    for (size_t v=0;v<nvar;v++) d.variable[v] = d2.variable[v] + ((d2.variable[v]-d.variable[v])/double(std::pow(2.,(int)(tableau.order())-1)));
 
  }

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

• StepDoublingRKStepper.hh
• StepDoublingRKStepper.cc