1/*
2 [auto_generated]
3 boost/numeric/odeint/stepper/euler.hpp
4
5 [begin_description]
6 Implementation of the classical explicit Euler stepper. This method is really simple and should only
7 be used for demonstration purposes.
8 [end_description]
9
10 Copyright 2010-2013 Karsten Ahnert
11 Copyright 2010-2013 Mario Mulansky
12
13 Distributed under the Boost Software License, Version 1.0.
14 (See accompanying file LICENSE_1_0.txt or
15 copy at http://www.boost.org/LICENSE_1_0.txt)
16 */
17
18
19#ifndef BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED
20#define BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED
21
22
23#include <boost/numeric/odeint/stepper/base/explicit_stepper_base.hpp>
24#include <boost/numeric/odeint/util/resizer.hpp>
25#include <boost/numeric/odeint/algebra/range_algebra.hpp>
26#include <boost/numeric/odeint/algebra/default_operations.hpp>
27#include <boost/numeric/odeint/algebra/algebra_dispatcher.hpp>
28#include <boost/numeric/odeint/algebra/operations_dispatcher.hpp>
29
30namespace boost {
31namespace numeric {
32namespace odeint {
33
34
35template<
36class State ,
37class Value = double ,
38class Deriv = State ,
39class Time = Value ,
40class Algebra = typename algebra_dispatcher< State >::algebra_type ,
41class Operations = typename operations_dispatcher< State >::operations_type ,
42class Resizer = initially_resizer
43>
44#ifndef DOXYGEN_SKIP
45class euler
46: public explicit_stepper_base<
47 euler< State , Value , Deriv , Time , Algebra , Operations , Resizer > ,
48 1 , State , Value , Deriv , Time , Algebra , Operations , Resizer >
49#else
50class euler : public explicit_stepper_base
51#endif
52{
53public :
54
55 #ifndef DOXYGEN_SKIP
56 typedef explicit_stepper_base< euler< State , Value , Deriv , Time , Algebra , Operations , Resizer > , 1 , State , Value , Deriv , Time , Algebra , Operations , Resizer > stepper_base_type;
57 #else
58 typedef explicit_stepper_base< euler< ... > , ... > stepper_base_type;
59 #endif
60 typedef typename stepper_base_type::state_type state_type;
61 typedef typename stepper_base_type::value_type value_type;
62 typedef typename stepper_base_type::deriv_type deriv_type;
63 typedef typename stepper_base_type::time_type time_type;
64 typedef typename stepper_base_type::algebra_type algebra_type;
65 typedef typename stepper_base_type::operations_type operations_type;
66 typedef typename stepper_base_type::resizer_type resizer_type;
67
68 #ifndef DOXYGEN_SKIP
69 typedef typename stepper_base_type::stepper_type stepper_type;
70 typedef typename stepper_base_type::wrapped_state_type wrapped_state_type;
71 typedef typename stepper_base_type::wrapped_deriv_type wrapped_deriv_type;
72 #endif
73
74
75 euler( const algebra_type &algebra = algebra_type() ) : stepper_base_type( algebra )
76 { }
77
78 template< class System , class StateIn , class DerivIn , class StateOut >
79 void do_step_impl( System /* system */ , const StateIn &in , const DerivIn &dxdt , time_type /* t */ , StateOut &out , time_type dt )
80 {
81 stepper_base_type::m_algebra.for_each3( out , in , dxdt ,
82 typename operations_type::template scale_sum2< value_type , time_type >( 1.0 , dt ) );
83
84 }
85
86 template< class StateOut , class StateIn1 , class StateIn2 >
87 void calc_state( StateOut &x , time_type t , const StateIn1 &old_state , time_type t_old , const StateIn2 & /*current_state*/ , time_type /* t_new */ ) const
88 {
89 const time_type delta = t - t_old;
90 stepper_base_type::m_algebra.for_each3( x , old_state , stepper_base_type::m_dxdt.m_v ,
91 typename operations_type::template scale_sum2< value_type , time_type >( 1.0 , delta ) );
92 }
93
94 template< class StateType >
95 void adjust_size( const StateType &x )
96 {
97 stepper_base_type::adjust_size( x );
98 }
99};
100
101
102
103/********** DOXYGEN ***********/
104
105/**
106 * \class euler
107 * \brief An implementation of the Euler method.
108 *
109 * The Euler method is a very simply solver for ordinary differential equations. This method should not be used
110 * for real applications. It is only useful for demonstration purposes. Step size control is not provided but
111 * trivial continuous output is available.
112 *
113 * This class derives from explicit_stepper_base and inherits its interface via CRTP (current recurring template pattern),
114 * see explicit_stepper_base
115 *
116 * \tparam State The state type.
117 * \tparam Value The value type.
118 * \tparam Deriv The type representing the time derivative of the state.
119 * \tparam Time The time representing the independent variable - the time.
120 * \tparam Algebra The algebra type.
121 * \tparam Operations The operations type.
122 * \tparam Resizer The resizer policy type.
123 */
124
125 /**
126 * \fn euler::euler( const algebra_type &algebra )
127 * \brief Constructs the euler class. This constructor can be used as a default
128 * constructor of the algebra has a default constructor.
129 * \param algebra A copy of algebra is made and stored inside explicit_stepper_base.
130 */
131
132 /**
133 * \fn euler::do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt )
134 * \brief This method performs one step. The derivative `dxdt` of `in` at the time `t` is passed to the method.
135 * The result is updated out of place, hence the input is in `in` and the output in `out`.
136 * Access to this step functionality is provided by explicit_stepper_base and
137 * `do_step_impl` should not be called directly.
138 *
139 * \param system The system function to solve, hence the r.h.s. of the ODE. It must fulfill the
140 * Simple System concept.
141 * \param in The state of the ODE which should be solved. in is not modified in this method
142 * \param dxdt The derivative of x at t.
143 * \param t The value of the time, at which the step should be performed.
144 * \param out The result of the step is written in out.
145 * \param dt The step size.
146 */
147
148
149 /**
150 * \fn euler::calc_state( StateOut &x , time_type t , const StateIn1 &old_state , time_type t_old , const StateIn2 &current_state , time_type t_new ) const
151 * \brief This method is used for continuous output and it calculates the state `x` at a time `t` from the
152 * knowledge of two states `old_state` and `current_state` at time points `t_old` and `t_new`.
153 */
154
155 /**
156 * \fn euler::adjust_size( const StateType &x )
157 * \brief Adjust the size of all temporaries in the stepper manually.
158 * \param x A state from which the size of the temporaries to be resized is deduced.
159 */
160
161} // odeint
162} // numeric
163} // boost
164
165
166#endif // BOOST_NUMERIC_ODEINT_STEPPER_EULER_HPP_INCLUDED
167

source code of boost/boost/numeric/odeint/stepper/euler.hpp