ceph/src/boost/boost/numeric/odeint/stepper/runge_kutta4_classic.hpp

   1 /*
   2  [auto_generated]
   3  boost/numeric/odeint/stepper/runge_kutta4_classic.hpp
   4
   5  [begin_description]
   6  Implementation for the classical Runge Kutta stepper.
   7  [end_description]
   8
   9  Copyright 2010-2013 Karsten Ahnert
  10  Copyright 2010-2013 Mario Mulansky
  11  Copyright 2012 Christoph Koke
  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_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED
  20 #define BOOST_NUMERIC_ODEINT_STEPPER_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED
  21
  22
  23
  24 #include <boost/numeric/odeint/stepper/base/explicit_stepper_base.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
  30 #include <boost/numeric/odeint/util/state_wrapper.hpp>
  31 #include <boost/numeric/odeint/util/is_resizeable.hpp>
  32 #include <boost/numeric/odeint/util/resizer.hpp>
  33
  34 namespace boost {
  35 namespace numeric {
  36 namespace odeint {
  37
  38 template<
  39 class State ,
  40 class Value = double ,
  41 class Deriv = State ,
  42 class Time = Value ,
  43 class Algebra = typename algebra_dispatcher< State >::algebra_type ,
  44 class Operations = typename operations_dispatcher< State >::operations_type ,
  45 class Resizer = initially_resizer
  46 >
  47 #ifndef DOXYGEN_SKIP
  48 class runge_kutta4_classic
  49 : public explicit_stepper_base<
  50   runge_kutta4_classic< State , Value , Deriv , Time , Algebra , Operations , Resizer > ,
  51   4 , State , Value , Deriv , Time , Algebra , Operations , Resizer >
  52 #else
  53 class runge_kutta4_classic : public explicit_stepper_base
  54 #endif
  55 {
  56
  57 public :
  58
  59     #ifndef DOXYGEN_SKIP
  60     typedef explicit_stepper_base<
  61     runge_kutta4_classic< State , Value , Deriv , Time , Algebra , Operations , Resizer > ,
  62     4 , State , Value , Deriv , Time , Algebra , Operations , Resizer > stepper_base_type;
  63     #else
  64     typedef explicit_stepper_base< runge_kutta4_classic< ... > , ... > stepper_base_type;
  65     #endif
  66
  67     typedef typename stepper_base_type::state_type state_type;
  68     typedef typename stepper_base_type::value_type value_type;
  69     typedef typename stepper_base_type::deriv_type deriv_type;
  70     typedef typename stepper_base_type::time_type time_type;
  71     typedef typename stepper_base_type::algebra_type algebra_type;
  72     typedef typename stepper_base_type::operations_type operations_type;
  73     typedef typename stepper_base_type::resizer_type resizer_type;
  74
  75     #ifndef DOXYGEN_SKIP
  76     typedef typename stepper_base_type::stepper_type stepper_type;
  77     typedef typename stepper_base_type::wrapped_state_type wrapped_state_type;
  78     typedef typename stepper_base_type::wrapped_deriv_type wrapped_deriv_type;
  79     #endif // DOXYGEN_SKIP
  80
  81
  82
  83     runge_kutta4_classic( const algebra_type &algebra = algebra_type() ) : stepper_base_type( algebra )
  84     { }
  85
  86
  87     template< class System , class StateIn , class DerivIn , class StateOut >
  88     void do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt )
  89     {
  90         // ToDo : check if size of in,dxdt,out are equal?
  91
  92         static const value_type val1 = static_cast< value_type >( 1 );
  93
  94         m_resizer.adjust_size( in , detail::bind( &stepper_type::template resize_impl< StateIn > , detail::ref( *this ) , detail::_1 ) );
  95
  96         typename odeint::unwrap_reference< System >::type &sys = system;
  97
  98         const time_type dh = dt / static_cast< value_type >( 2 );
  99         const time_type th = t + dh;
 100
 101         // dt * dxdt = k1
 102         // m_x_tmp = x + dh*dxdt
 103         stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , dxdt ,
 104                 typename operations_type::template scale_sum2< value_type , time_type >( val1 , dh ) );
 105
 106
 107         // dt * m_dxt = k2
 108         sys( m_x_tmp.m_v , m_dxt.m_v , th );
 109
 110         // m_x_tmp = x + dh*m_dxt
 111         stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , m_dxt.m_v ,
 112                 typename operations_type::template scale_sum2< value_type , time_type >( val1 , dh ) );
 113
 114
 115         // dt * m_dxm = k3
 116         sys( m_x_tmp.m_v , m_dxm.m_v , th );
 117         //m_x_tmp = x + dt*m_dxm
 118         stepper_base_type::m_algebra.for_each3( m_x_tmp.m_v , in , m_dxm.m_v ,
 119                 typename operations_type::template scale_sum2< value_type , time_type >( val1 , dt ) );
 120
 121
 122         // dt * m_dxh = k4
 123         sys( m_x_tmp.m_v , m_dxh.m_v , t + dt );
 124
 125         //x += dt/6 * ( m_dxdt + m_dxt + val2*m_dxm )
 126         time_type dt6 = dt / static_cast< value_type >( 6 );
 127         time_type dt3 = dt / static_cast< value_type >( 3 );
 128         stepper_base_type::m_algebra.for_each6( out , in , dxdt , m_dxt.m_v , m_dxm.m_v , m_dxh.m_v ,
 129                                              typename operations_type::template scale_sum5< value_type , time_type , time_type , time_type , time_type >( 1.0 , dt6 , dt3 , dt3 , dt6 ) );
 130
 131         // x += dt/6 * m_dxdt + dt/3 * m_dxt )
 132         // stepper_base_type::m_algebra.for_each4( out , in , dxdt , m_dxt.m_v ,
 133         //                                         typename operations_type::template scale_sum3< value_type , time_type , time_type >( 1.0 , dt6 , dt3 ) );
 134         // // x += dt/3 * m_dxm + dt/6 * m_dxh )
 135         // stepper_base_type::m_algebra.for_each4( out , out , m_dxm.m_v , m_dxh.m_v ,
 136         //                                         typename operations_type::template scale_sum3< value_type , time_type , time_type >( 1.0 , dt3 , dt6 ) );
 137
 138     }
 139
 140     template< class StateType >
 141     void adjust_size( const StateType &x )
 142     {
 143         resize_impl( x );
 144         stepper_base_type::adjust_size( x );
 145     }
 146
 147 private:
 148
 149     template< class StateIn >
 150     bool resize_impl( const StateIn &x )
 151     {
 152         bool resized = false;
 153         resized |= adjust_size_by_resizeability( m_x_tmp , x , typename is_resizeable<state_type>::type() );
 154         resized |= adjust_size_by_resizeability( m_dxm , x , typename is_resizeable<deriv_type>::type() );
 155         resized |= adjust_size_by_resizeability( m_dxt , x , typename is_resizeable<deriv_type>::type() );
 156         resized |= adjust_size_by_resizeability( m_dxh , x , typename is_resizeable<deriv_type>::type() );
 157         return resized;
 158     }
 159
 160
 161     resizer_type m_resizer;
 162
 163     wrapped_deriv_type m_dxt;
 164     wrapped_deriv_type m_dxm;
 165     wrapped_deriv_type m_dxh;
 166     wrapped_state_type m_x_tmp;
 167
 168 };
 169
 170
 171 /********* DOXYGEN *********/
 172
 173 /**
 174  * \class runge_kutta4_classic
 175  * \brief The classical Runge-Kutta stepper of fourth order.
 176  *
 177  * The Runge-Kutta method of fourth order is one standard method for
 178  * solving ordinary differential equations and is widely used, see also
 179  * <a href="http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods">en.wikipedia.org/wiki/Runge-Kutta_methods</a>
 180  * The method is explicit and fulfills the Stepper concept. Step size control
 181  * or continuous output are not provided.  This class implements the method directly, hence the
 182  * generic Runge-Kutta algorithm is not used.
 183  *
 184  * This class derives from explicit_stepper_base and inherits its interface via
 185  * CRTP (current recurring template pattern). For more details see
 186  * explicit_stepper_base.
 187  *
 188  * \tparam State The state type.
 189  * \tparam Value The value type.
 190  * \tparam Deriv The type representing the time derivative of the state.
 191  * \tparam Time The time representing the independent variable - the time.
 192  * \tparam Algebra The algebra type.
 193  * \tparam Operations The operations type.
 194  * \tparam Resizer The resizer policy type.
 195  */
 196
 197     /**
 198      * \fn runge_kutta4_classic::runge_kutta4_classic( const algebra_type &algebra )
 199      * \brief Constructs the runge_kutta4_classic class. This constructor can be used as a default
 200      * constructor if the algebra has a default constructor.
 201      * \param algebra A copy of algebra is made and stored inside explicit_stepper_base.
 202      */
 203
 204
 205     /**
 206      * \fn runge_kutta4_classic::do_step_impl( System system , const StateIn &in , const DerivIn &dxdt , time_type t , StateOut &out , time_type dt )
 207      * \brief This method performs one step. The derivative `dxdt` of `in` at the time `t` is passed to the method.
 208      * The result is updated out of place, hence the input is in `in` and the output in `out`.
 209      * Access to this step functionality is provided by explicit_stepper_base and
 210      * `do_step_impl` should not be called directly.
 211      *
 212      * \param system The system function to solve, hence the r.h.s. of the ODE. It must fulfill the
 213      *               Simple System concept.
 214      * \param in The state of the ODE which should be solved. in is not modified in this method
 215      * \param dxdt The derivative of x at t.
 216      * \param t The value of the time, at which the step should be performed.
 217      * \param out The result of the step is written in out.
 218      * \param dt The step size.
 219      */
 220
 221     /**
 222      * \fn runge_kutta4_classic::adjust_size( const StateType &x )
 223      * \brief Adjust the size of all temporaries in the stepper manually.
 224      * \param x A state from which the size of the temporaries to be resized is deduced.
 225      */
 226
 227 } // odeint
 228 } // numeric
 229 } // boost
 230
 231
 232 #endif // BOOST_NUMERIC_ODEINT_STEPPER_RUNGE_KUTTA4_CLASSIC_HPP_INCLUDED