/* [auto_generated] boost/numeric/odeint/stepper/euler.hpp [begin_description] Implementation of the classical explicit Euler stepper. This method is really simple and should only be used for demonstration purposes. [end_description] Copyright 2010-2013 Karsten Ahnert Copyright 2010-2013 Mario Mulansky Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) */ #ifndef BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED #define BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED #include #include #include #include #include #include namespace boost { namespace numeric { namespace odeint { template< class State , class Value = double , class Deriv = State , class Time = Value , class Algebra = typename algebra_dispatcher< State >::algebra_type , class Operations = typename operations_dispatcher< State >::operations_type , class Resizer = initially_resizer > #ifndef DOXYGEN_SKIP class euler : public explicit_stepper_base< euler< State , Value , Deriv , Time , Algebra , Operations , Resizer > , 1 , State , Value , Deriv , Time , Algebra , Operations , Resizer > #else class euler : public explicit_stepper_base #endif { public : #ifndef DOXYGEN_SKIP typedef explicit_stepper_base< euler< State , Value , Deriv , Time , Algebra , Operations , Resizer > , 1 , State , Value , Deriv , Time , Algebra , Operations , Resizer > stepper_base_type; #else typedef explicit_stepper_base< euler< ... > , ... > stepper_base_type; #endif typedef typename stepper_base_type::state_type state_type; typedef typename stepper_base_type::value_type value_type; typedef typename stepper_base_type::deriv_type deriv_type; typedef typename stepper_base_type::time_type time_type; typedef typename stepper_base_type::algebra_type algebra_type; typedef typename stepper_base_type::operations_type operations_type; typedef typename stepper_base_type::resizer_type resizer_type; #ifndef DOXYGEN_SKIP typedef typename stepper_base_type::stepper_type stepper_type; typedef typename stepper_base_type::wrapped_state_type wrapped_state_type; typedef typename stepper_base_type::wrapped_deriv_type wrapped_deriv_type; #endif euler( const algebra_type &algebra = algebra_type() ) : stepper_base_type( algebra ) { } template< class System , class StateIn , class DerivIn , class StateOut > void do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt ) { stepper_base_type::m_algebra.for_each3( out , in , dxdt , typename operations_type::template scale_sum2< value_type , time_type >( 1.0 , dt ) ); } template< class StateOut , class StateIn1 , class StateIn2 > void calc_state( StateOut &x , time_type t , const StateIn1 &old_state , time_type t_old , const StateIn2 ¤t_state , time_type t_new ) const { const time_type delta = t - t_old; stepper_base_type::m_algebra.for_each3( x , old_state , stepper_base_type::m_dxdt.m_v , typename operations_type::template scale_sum2< value_type , time_type >( 1.0 , delta ) ); } template< class StateType > void adjust_size( const StateType &x ) { stepper_base_type::adjust_size( x ); } }; /********** DOXYGEN ***********/ /** * \class euler * \brief An implementation of the Euler method. * * The Euler method is a very simply solver for ordinary differential equations. This method should not be used * for real applications. It is only useful for demonstration purposes. Step size control is not provided but * trivial continuous output is available. * * This class derives from explicit_stepper_base and inherits its interface via CRTP (current recurring template pattern), * see explicit_stepper_base * * \tparam State The state type. * \tparam Value The value type. * \tparam Deriv The type representing the time derivative of the state. * \tparam Time The time representing the independent variable - the time. * \tparam Algebra The algebra type. * \tparam Operations The operations type. * \tparam Resizer The resizer policy type. */ /** * \fn euler::euler( const algebra_type &algebra ) * \brief Constructs the euler class. This constructor can be used as a default * constructor of the algebra has a default constructor. * \param algebra A copy of algebra is made and stored inside explicit_stepper_base. */ /** * \fn euler::do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt ) * \brief This method performs one step. The derivative `dxdt` of `in` at the time `t` is passed to the method. * The result is updated out of place, hence the input is in `in` and the output in `out`. * Access to this step functionality is provided by explicit_stepper_base and * `do_step_impl` should not be called directly. * * \param system The system function to solve, hence the r.h.s. of the ODE. It must fulfill the * Simple System concept. * \param in The state of the ODE which should be solved. in is not modified in this method * \param dxdt The derivative of x at t. * \param t The value of the time, at which the step should be performed. * \param out The result of the step is written in out. * \param dt The step size. */ /** * \fn euler::calc_state( StateOut &x , time_type t , const StateIn1 &old_state , time_type t_old , const StateIn2 ¤t_state , time_type t_new ) const * \brief This method is used for continuous output and it calculates the state `x` at a time `t` from the * knowledge of two states `old_state` and `current_state` at time points `t_old` and `t_new`. */ /** * \fn euler::adjust_size( const StateType &x ) * \brief Adjust the size of all temporaries in the stepper manually. * \param x A state from which the size of the temporaries to be resized is deduced. */ } // odeint } // numeric } // boost #endif // BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED