233 lines
9.3 KiB
Plaintext
233 lines
9.3 KiB
Plaintext
/*
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[auto_generated]
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boost/numeric/odeint/stepper/runge_kutta4_classic.hpp
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[begin_description]
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Implementation for the classical Runge Kutta stepper.
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[end_description]
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Copyright 2010-2013 Karsten Ahnert
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Copyright 2010-2013 Mario Mulansky
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Copyright 2012 Christoph Koke
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or
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copy at http://www.boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_NUMERIC_ODEINT_STEPPER_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED
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#define BOOST_NUMERIC_ODEINT_STEPPER_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED
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#include <boost/numeric/odeint/stepper/base/explicit_stepper_base.hpp>
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#include <boost/numeric/odeint/algebra/range_algebra.hpp>
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#include <boost/numeric/odeint/algebra/default_operations.hpp>
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#include <boost/numeric/odeint/algebra/algebra_dispatcher.hpp>
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#include <boost/numeric/odeint/algebra/operations_dispatcher.hpp>
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#include <boost/numeric/odeint/util/state_wrapper.hpp>
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#include <boost/numeric/odeint/util/is_resizeable.hpp>
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#include <boost/numeric/odeint/util/resizer.hpp>
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namespace boost {
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namespace numeric {
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namespace odeint {
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template<
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class State ,
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class Value = double ,
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class Deriv = State ,
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class Time = Value ,
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class Algebra = typename algebra_dispatcher< State >::algebra_type ,
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class Operations = typename operations_dispatcher< State >::operations_type ,
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class Resizer = initially_resizer
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>
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#ifndef DOXYGEN_SKIP
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class runge_kutta4_classic
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: public explicit_stepper_base<
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runge_kutta4_classic< State , Value , Deriv , Time , Algebra , Operations , Resizer > ,
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4 , State , Value , Deriv , Time , Algebra , Operations , Resizer >
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#else
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class runge_kutta4_classic : public explicit_stepper_base
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#endif
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{
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public :
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#ifndef DOXYGEN_SKIP
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typedef explicit_stepper_base<
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runge_kutta4_classic< State , Value , Deriv , Time , Algebra , Operations , Resizer > ,
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4 , State , Value , Deriv , Time , Algebra , Operations , Resizer > stepper_base_type;
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#else
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typedef explicit_stepper_base< runge_kutta4_classic< ... > , ... > stepper_base_type;
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#endif
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typedef typename stepper_base_type::state_type state_type;
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typedef typename stepper_base_type::value_type value_type;
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typedef typename stepper_base_type::deriv_type deriv_type;
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typedef typename stepper_base_type::time_type time_type;
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typedef typename stepper_base_type::algebra_type algebra_type;
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typedef typename stepper_base_type::operations_type operations_type;
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typedef typename stepper_base_type::resizer_type resizer_type;
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#ifndef DOXYGEN_SKIP
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typedef typename stepper_base_type::stepper_type stepper_type;
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typedef typename stepper_base_type::wrapped_state_type wrapped_state_type;
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typedef typename stepper_base_type::wrapped_deriv_type wrapped_deriv_type;
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#endif // DOXYGEN_SKIP
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runge_kutta4_classic( const algebra_type &algebra = algebra_type() ) : stepper_base_type( algebra )
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{ }
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template< class System , class StateIn , class DerivIn , class StateOut >
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void do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt )
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{
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// ToDo : check if size of in,dxdt,out are equal?
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static const value_type val1 = static_cast< value_type >( 1 );
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m_resizer.adjust_size( in , detail::bind( &stepper_type::template resize_impl< StateIn > , detail::ref( *this ) , detail::_1 ) );
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typename odeint::unwrap_reference< System >::type &sys = system;
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const time_type dh = dt / static_cast< value_type >( 2 );
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const time_type th = t + dh;
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// dt * dxdt = k1
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// m_x_tmp = x + dh*dxdt
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stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , dxdt ,
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typename operations_type::template scale_sum2< value_type , time_type >( val1 , dh ) );
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// dt * m_dxt = k2
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sys( m_x_tmp.m_v , m_dxt.m_v , th );
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// m_x_tmp = x + dh*m_dxt
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stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , m_dxt.m_v ,
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typename operations_type::template scale_sum2< value_type , time_type >( val1 , dh ) );
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// dt * m_dxm = k3
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sys( m_x_tmp.m_v , m_dxm.m_v , th );
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//m_x_tmp = x + dt*m_dxm
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stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , m_dxm.m_v ,
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typename operations_type::template scale_sum2< value_type , time_type >( val1 , dt ) );
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// dt * m_dxh = k4
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sys( m_x_tmp.m_v , m_dxh.m_v , t + dt );
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//x += dt/6 * ( m_dxdt + m_dxt + val2*m_dxm )
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time_type dt6 = dt / static_cast< value_type >( 6 );
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time_type dt3 = dt / static_cast< value_type >( 3 );
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stepper_base_type::m_algebra.for_each6( out , in , dxdt , m_dxt.m_v , m_dxm.m_v , m_dxh.m_v ,
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typename operations_type::template scale_sum5< value_type , time_type , time_type , time_type , time_type >( 1.0 , dt6 , dt3 , dt3 , dt6 ) );
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// x += dt/6 * m_dxdt + dt/3 * m_dxt )
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// stepper_base_type::m_algebra.for_each4( out , in , dxdt , m_dxt.m_v ,
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// typename operations_type::template scale_sum3< value_type , time_type , time_type >( 1.0 , dt6 , dt3 ) );
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// // x += dt/3 * m_dxm + dt/6 * m_dxh )
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// stepper_base_type::m_algebra.for_each4( out , out , m_dxm.m_v , m_dxh.m_v ,
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// typename operations_type::template scale_sum3< value_type , time_type , time_type >( 1.0 , dt3 , dt6 ) );
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}
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template< class StateType >
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void adjust_size( const StateType &x )
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{
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resize_impl( x );
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stepper_base_type::adjust_size( x );
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}
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private:
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template< class StateIn >
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bool resize_impl( const StateIn &x )
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{
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bool resized = false;
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resized |= adjust_size_by_resizeability( m_x_tmp , x , typename is_resizeable<state_type>::type() );
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resized |= adjust_size_by_resizeability( m_dxm , x , typename is_resizeable<deriv_type>::type() );
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resized |= adjust_size_by_resizeability( m_dxt , x , typename is_resizeable<deriv_type>::type() );
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resized |= adjust_size_by_resizeability( m_dxh , x , typename is_resizeable<deriv_type>::type() );
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return resized;
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}
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resizer_type m_resizer;
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wrapped_deriv_type m_dxt;
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wrapped_deriv_type m_dxm;
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wrapped_deriv_type m_dxh;
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wrapped_state_type m_x_tmp;
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};
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/********* DOXYGEN *********/
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/**
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* \class runge_kutta4_classic
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* \brief The classical Runge-Kutta stepper of fourth order.
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*
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* The Runge-Kutta method of fourth order is one standard method for
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* solving ordinary differential equations and is widely used, see also
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* <a href="http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods">en.wikipedia.org/wiki/Runge-Kutta_methods</a>
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* The method is explicit and fulfills the Stepper concept. Step size control
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* or continuous output are not provided. This class implements the method directly, hence the
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* generic Runge-Kutta algorithm is not used.
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*
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* This class derives from explicit_stepper_base and inherits its interface via
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* CRTP (current recurring template pattern). For more details see
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* explicit_stepper_base.
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*
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* \tparam State The state type.
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* \tparam Value The value type.
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* \tparam Deriv The type representing the time derivative of the state.
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* \tparam Time The time representing the independent variable - the time.
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* \tparam Algebra The algebra type.
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* \tparam Operations The operations type.
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* \tparam Resizer The resizer policy type.
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*/
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/**
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* \fn runge_kutta4_classic::runge_kutta4_classic( const algebra_type &algebra )
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* \brief Constructs the runge_kutta4_classic class. This constructor can be used as a default
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* constructor if the algebra has a default constructor.
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* \param algebra A copy of algebra is made and stored inside explicit_stepper_base.
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*/
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/**
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* \fn runge_kutta4_classic::do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt )
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* \brief This method performs one step. The derivative `dxdt` of `in` at the time `t` is passed to the method.
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* The result is updated out of place, hence the input is in `in` and the output in `out`.
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* Access to this step functionality is provided by explicit_stepper_base and
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* `do_step_impl` should not be called directly.
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*
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* \param system The system function to solve, hence the r.h.s. of the ODE. It must fulfill the
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* Simple System concept.
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* \param in The state of the ODE which should be solved. in is not modified in this method
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* \param dxdt The derivative of x at t.
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* \param t The value of the time, at which the step should be performed.
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* \param out The result of the step is written in out.
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* \param dt The step size.
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*/
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/**
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* \fn runge_kutta4_classic::adjust_size( const StateType &x )
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* \brief Adjust the size of all temporaries in the stepper manually.
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* \param x A state from which the size of the temporaries to be resized is deduced.
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*/
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} // odeint
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} // numeric
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} // boost
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#endif // BOOST_NUMERIC_ODEINT_STEPPER_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED
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