oomph::RungeKutta< ORDER > Class Template Reference

#include <explicit_timesteppers.h>

Inheritance diagram for oomph::RungeKutta< ORDER >:

Public Member Functions
	RungeKutta ()
	Constructor, set the type. More...
	RungeKutta (const RungeKutta &)=delete
	Broken copy constructor. More...
void	operator= (const RungeKutta &)=delete
	Broken assignment operator. More...
void	timestep (ExplicitTimeSteppableObject *const &object_pt, const double &dt)
	Function that is used to advance time in the object. More...
void	timestep (ExplicitTimeSteppableObject *const &object_pt, const double &dt)
	Explicit specialisation for fourth-order RK scheme. More...
void	timestep (ExplicitTimeSteppableObject *const &object_pt, const double &dt)
	Explicit specialisation for second-order RK scheme. More...
Public Member Functions inherited from oomph::ExplicitTimeStepper
	ExplicitTimeStepper ()
	Empty Constructor. More...
	ExplicitTimeStepper (const ExplicitTimeStepper &)=delete
	Broken copy constructor. More...
void	operator= (const ExplicitTimeStepper &)=delete
	Broken assignment operator. More...
virtual	~ExplicitTimeStepper ()
	Empty virtual destructor — no memory is allocated in this class. More...

Additional Inherited Members
Protected Attributes inherited from oomph::ExplicitTimeStepper
std::string	Type

Detailed Description

template<unsigned ORDER>
class oomph::RungeKutta< ORDER >

=========================================================== Standard Runge Kutta Timestepping

Constructor & Destructor Documentation

RungeKutta() [1/2]

template<unsigned ORDER>

oomph::RungeKutta< ORDER >::RungeKutta ( )

inline

Constructor, set the type.

    {
      Type = "RungeKutta";
    }

References oomph::ExplicitTimeStepper::Type.

RungeKutta() [2/2]

template<unsigned ORDER>

oomph::RungeKutta< ORDER >::RungeKutta ( const RungeKutta< ORDER > &  )

delete

Broken copy constructor.

Member Function Documentation

operator=()

template<unsigned ORDER>

void oomph::RungeKutta< ORDER >::operator= ( const RungeKutta< ORDER > &  )

delete

Broken assignment operator.

timestep() [1/3]

void oomph::RungeKutta< 4 >::timestep ( ExplicitTimeSteppableObject *const &  object_pt, const double &  dt  )

virtual

Explicit specialisation for fourth-order RK scheme.

Implements oomph::ExplicitTimeStepper.

  {
    object_pt->actions_before_explicit_timestep();
 
    // Stage 1
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // Store the initial values and initial time
    DoubleVector u;
    object_pt->get_dofs(u);
 
    // Now get the first unknowns
    DoubleVector k1;
    object_pt->get_dvaluesdt(k1);
 
    // Add to the residuals
    object_pt->add_to_dofs(0.5 * dt, k1);
    // Increment the time
    object_pt->time() += 0.5 * dt;
    object_pt->actions_after_explicit_stage();
 
 
    // Stage 2
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // Get the next unknowns
    DoubleVector k2;
    object_pt->get_dvaluesdt(k2);
 
    // Now reset the residuals
    object_pt->set_dofs(u);
    object_pt->add_to_dofs(0.5 * dt, k2);
    // Time remains the same
    object_pt->actions_after_explicit_stage();
 
    // Stage 3
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // Get the next unknowns
    DoubleVector k3;
    object_pt->get_dvaluesdt(k3);
 
    // Now reset the residuals
    object_pt->set_dofs(u);
    object_pt->add_to_dofs(dt, k3);
    // Increment the time (now at initial_time + dt)
    object_pt->time() += 0.5 * dt;
    object_pt->actions_after_explicit_stage();
 
    // Stage 4
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // Get the final unknowns
    DoubleVector k4;
    object_pt->get_dvaluesdt(k4);
 
    // Set the final values of the unknowns
    object_pt->set_dofs(u);
    object_pt->add_to_dofs((dt / 6.0), k1);
    object_pt->add_to_dofs((dt / 3.0), k2);
    object_pt->add_to_dofs((dt / 3.0), k3);
    object_pt->add_to_dofs((dt / 6.0), k4);
    object_pt->actions_after_explicit_stage();
 
    object_pt->actions_after_explicit_timestep();
  }

References oomph::ExplicitTimeSteppableObject::actions_after_explicit_stage(), oomph::ExplicitTimeSteppableObject::actions_after_explicit_timestep(), oomph::ExplicitTimeSteppableObject::actions_before_explicit_stage(), oomph::ExplicitTimeSteppableObject::actions_before_explicit_timestep(), oomph::ExplicitTimeSteppableObject::add_to_dofs(), oomph::ExplicitTimeSteppableObject::get_dofs(), oomph::ExplicitTimeSteppableObject::get_dvaluesdt(), oomph::ExplicitTimeSteppableObject::set_dofs(), and oomph::ExplicitTimeSteppableObject::time().

timestep() [2/3]

void oomph::RungeKutta< 2 >::timestep ( ExplicitTimeSteppableObject *const &  object_pt, const double &  dt  )

virtual

Explicit specialisation for second-order RK scheme.

Implements oomph::ExplicitTimeStepper.

  {
    object_pt->actions_before_explicit_timestep();
 
    // Stage 1
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // Store the initial values
    DoubleVector u;
    object_pt->get_dofs(u);
 
    // Get f1 (time derivative at t0, y0) and add to dofs
    DoubleVector f1;
    object_pt->get_dvaluesdt(f1);
    object_pt->add_to_dofs(dt, f1);
 
    // Advance time to t1 = t0 + dt
    object_pt->time() += dt;
 
    object_pt->actions_after_explicit_stage();
 
 
    // Stage 2
    // ============================================================
    object_pt->actions_before_explicit_stage();
 
    // get f2 (with t=t1, y = y0 + h f0)
    DoubleVector f2;
    object_pt->get_dvaluesdt(f2);
 
    // Final answer is starting dofs + h/2 * (f1 + f2)
    object_pt->set_dofs(u);
    object_pt->add_to_dofs(0.5 * dt, f1);
    object_pt->add_to_dofs(0.5 * dt, f2);
 
    object_pt->actions_after_explicit_stage();
 
    // Done, do actions
    object_pt->actions_after_explicit_timestep();
  }

References oomph::ExplicitTimeSteppableObject::actions_after_explicit_stage(), oomph::ExplicitTimeSteppableObject::actions_after_explicit_timestep(), oomph::ExplicitTimeSteppableObject::actions_before_explicit_stage(), oomph::ExplicitTimeSteppableObject::actions_before_explicit_timestep(), oomph::ExplicitTimeSteppableObject::add_to_dofs(), Global_parameters::f1(), Global_parameters::f2(), oomph::ExplicitTimeSteppableObject::get_dofs(), oomph::ExplicitTimeSteppableObject::get_dvaluesdt(), oomph::ExplicitTimeSteppableObject::set_dofs(), and oomph::ExplicitTimeSteppableObject::time().

timestep() [3/3]

template<unsigned ORDER>

void oomph::RungeKutta< ORDER >::timestep ( ExplicitTimeSteppableObject *const &  object_pt, const double &  dt  )

virtual

Function that is used to advance time in the object.

Implements oomph::ExplicitTimeStepper.

  {
    std::ostringstream error_stream;
    error_stream << "Timestep not implemented for order " << ORDER << "\n";
    throw OomphLibError(
      error_stream.str(), OOMPH_CURRENT_FUNCTION, OOMPH_EXCEPTION_LOCATION);
  }

References OOMPH_CURRENT_FUNCTION, and OOMPH_EXCEPTION_LOCATION.

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

• explicit_timesteppers.h
• explicit_timesteppers.cc