boost/numeric/odeint/stepper/velocity_verlet.hpp
/* [auto_generated] boost/numeric/odeint/stepper/velocity_verlet.hpp [begin_description] tba. [end_description] Copyright 2009-2012 Karsten Ahnert Copyright 2009-2012 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_VELOCITY_VERLET_HPP_DEFINED #define BOOST_NUMERIC_ODEINT_STEPPER_VELOCITY_VERLET_HPP_DEFINED #include <boost/numeric/odeint/stepper/base/algebra_stepper_base.hpp> #include <boost/numeric/odeint/stepper/stepper_categories.hpp> #include <boost/numeric/odeint/algebra/algebra_dispatcher.hpp> #include <boost/numeric/odeint/algebra/operations_dispatcher.hpp> #include <boost/numeric/odeint/util/resizer.hpp> #include <boost/numeric/odeint/util/state_wrapper.hpp> #include <boost/numeric/odeint/util/unwrap_reference.hpp> #include <boost/numeric/odeint/util/bind.hpp> #include <boost/numeric/odeint/util/copy.hpp> #include <boost/numeric/odeint/util/resizer.hpp> // #include <boost/numeric/odeint/util/is_pair.hpp> // #include <boost/array.hpp> namespace boost { namespace numeric { namespace odeint { template < class Coor , class Velocity = Coor , class Value = double , class Acceleration = Coor , class Time = Value , class TimeSq = Time , class Algebra = typename algebra_dispatcher< Coor >::algebra_type , class Operations = typename operations_dispatcher< Coor >::operations_type , class Resizer = initially_resizer > class velocity_verlet : public algebra_stepper_base< Algebra , Operations > { public: typedef algebra_stepper_base< Algebra , Operations > algebra_stepper_base_type; typedef typename algebra_stepper_base_type::algebra_type algebra_type; typedef typename algebra_stepper_base_type::operations_type operations_type; typedef Coor coor_type; typedef Velocity velocity_type; typedef Acceleration acceleration_type; typedef std::pair< coor_type , velocity_type > state_type; typedef std::pair< velocity_type , acceleration_type > deriv_type; typedef state_wrapper< acceleration_type > wrapped_acceleration_type; typedef Value value_type; typedef Time time_type; typedef TimeSq time_square_type; typedef Resizer resizer_type; typedef stepper_tag stepper_category; typedef unsigned short order_type; static const order_type order_value = 1; /** * \return Returns the order of the stepper. */ order_type order( void ) const { return order_value; } velocity_verlet( const algebra_type & algebra = algebra_type() ) : algebra_stepper_base_type( algebra ) , m_first_call( true ) , m_a1() , m_a2() , m_current_a1( true ) { } template< class System , class StateInOut > void do_step( System system , StateInOut & x , time_type t , time_type dt ) { do_step_v1( system , x , t , dt ); } template< class System , class StateInOut > void do_step( System system , const StateInOut & x , time_type t , time_type dt ) { do_step_v1( system , x , t , dt ); } template< class System , class CoorIn , class VelocityIn , class AccelerationIn , class CoorOut , class VelocityOut , class AccelerationOut > void do_step( System system , CoorIn const & qin , VelocityIn const & pin , AccelerationIn const & ain , CoorOut & qout , VelocityOut & pout , AccelerationOut & aout , time_type t , time_type dt ) { const value_type one = static_cast< value_type >( 1.0 ); const value_type one_half = static_cast< value_type >( 0.5 ); algebra_stepper_base_type::m_algebra.for_each4( qout , qin , pin , ain , typename operations_type::template scale_sum3< value_type , time_type , time_square_type >( one , one * dt , one_half * dt * dt ) ); typename odeint::unwrap_reference< System >::type & sys = system; sys( qout , pin , aout , t + dt ); algebra_stepper_base_type::m_algebra.for_each4( pout , pin , ain , aout , typename operations_type::template scale_sum3< value_type , time_type , time_type >( one , one_half * dt , one_half * dt ) ); } template< class StateIn > void adjust_size( const StateIn & x ) { if( resize_impl( x ) ) m_first_call = true; } void reset( void ) { m_first_call = true; } /** * \fn velocity_verlet::initialize( const AccelerationIn &qin ) * \brief Initializes the internal state of the stepper. * \param deriv The acceleration of x. The next call of `do_step` expects that the acceleration of `x` passed to `do_step` * has the value of `qin`. */ template< class AccelerationIn > void initialize( const AccelerationIn & ain ) { // alloc a m_resizer.adjust_size( ain , detail::bind( &velocity_verlet::template resize_impl< AccelerationIn > , detail::ref( *this ) , detail::_1 ) ); boost::numeric::odeint::copy( ain , get_current_acc() ); m_first_call = false; } template< class System , class CoorIn , class VelocityIn > void initialize( System system , const CoorIn & qin , const VelocityIn & pin , time_type t ) { m_resizer.adjust_size( qin , detail::bind( &velocity_verlet::template resize_impl< CoorIn > , detail::ref( *this ) , detail::_1 ) ); initialize_acc( system , qin , pin , t ); } bool is_initialized( void ) const { return ! m_first_call; } private: template< class System , class CoorIn , class VelocityIn > void initialize_acc( System system , const CoorIn & qin , const VelocityIn & pin , time_type t ) { typename odeint::unwrap_reference< System >::type & sys = system; sys( qin , pin , get_current_acc() , t ); m_first_call = false; } template< class System , class StateInOut > void do_step_v1( System system , StateInOut & x , time_type t , time_type dt ) { typedef typename odeint::unwrap_reference< StateInOut >::type state_in_type; typedef typename odeint::unwrap_reference< typename state_in_type::first_type >::type coor_in_type; typedef typename odeint::unwrap_reference< typename state_in_type::second_type >::type momentum_in_type; typedef typename boost::remove_reference< coor_in_type >::type xyz_type; state_in_type & statein = x; coor_in_type & qinout = statein.first; momentum_in_type & pinout = statein.second; // alloc a if( m_resizer.adjust_size( qinout , detail::bind( &velocity_verlet::template resize_impl< xyz_type > , detail::ref( *this ) , detail::_1 ) ) || m_first_call ) { initialize_acc( system , qinout , pinout , t ); } // check first do_step( system , qinout , pinout , get_current_acc() , qinout , pinout , get_old_acc() , t , dt ); toggle_current_acc(); } template< class StateIn > bool resize_impl( const StateIn & x ) { bool resized = false; resized |= adjust_size_by_resizeability( m_a1 , x , typename is_resizeable< acceleration_type >::type() ); resized |= adjust_size_by_resizeability( m_a2 , x , typename is_resizeable< acceleration_type >::type() ); return resized; } acceleration_type & get_current_acc( void ) { return m_current_a1 ? m_a1.m_v : m_a2.m_v ; } const acceleration_type & get_current_acc( void ) const { return m_current_a1 ? m_a1.m_v : m_a2.m_v ; } acceleration_type & get_old_acc( void ) { return m_current_a1 ? m_a2.m_v : m_a1.m_v ; } const acceleration_type & get_old_acc( void ) const { return m_current_a1 ? m_a2.m_v : m_a1.m_v ; } void toggle_current_acc( void ) { m_current_a1 = ! m_current_a1; } resizer_type m_resizer; bool m_first_call; wrapped_acceleration_type m_a1 , m_a2; bool m_current_a1; }; /** * \class velocity_verlet * \brief The Velocity-Verlet algorithm. * * <a href="http://en.wikipedia.org/wiki/Verlet_integration" >The Velocity-Verlet algorithm</a> is a method for simulation of molecular dynamics systems. It solves the ODE * a=f(r,v',t) where r are the coordinates, v are the velocities and a are the accelerations, hence v = dr/dt, a=dv/dt. * * \tparam Coor The type representing the coordinates. * \tparam Velocity The type representing the velocities. * \tparam Value The type value type. * \tparam Acceleration The type representing the acceleration. * \tparam Time The time representing the independent variable - the time. * \tparam TimeSq The time representing the square of the time. * \tparam Algebra The algebra. * \tparam Operations The operations type. * \tparam Resizer The resizer policy type. */ /** * \fn velocity_verlet::velocity_verlet( const algebra_type &algebra ) * \brief Constructs the velocity_verlet class. This constructor can be used as a default * constructor if the algebra has a default constructor. * \param algebra A copy of algebra is made and stored. */ /** * \fn velocity_verlet::do_step( System system , StateInOut &x , time_type t , time_type dt ) * \brief This method performs one step. It transforms the result in-place. * * It can be used like * \code * pair< coordinates , velocities > state; * stepper.do_step( sys , x , t , dt ); * \endcode * * \param system The system function to solve, hence the r.h.s. of the ordinary differential equation. It must fulfill the * Second Order System concept. * \param x The state of the ODE which should be solved. The state is pair of Coor and Velocity. * \param t The value of the time, at which the step should be performed. * \param dt The step size. */ /** * \fn velocity_verlet::do_step( System system , const StateInOut &x , time_type t , time_type dt ) * \brief This method performs one step. It transforms the result in-place. * * It can be used like * \code * pair< coordinates , velocities > state; * stepper.do_step( sys , x , t , dt ); * \endcode * * \param system The system function to solve, hence the r.h.s. of the ordinary differential equation. It must fulfill the * Second Order System concept. * \param x The state of the ODE which should be solved. The state is pair of Coor and Velocity. * \param t The value of the time, at which the step should be performed. * \param dt The step size. */ /** * \fn velocity_verlet::do_step( System system , CoorIn const & qin , VelocityIn const & pin , AccelerationIn const & ain , CoorOut & qout , VelocityOut & pout , AccelerationOut & aout , time_type t , time_type dt ) * \brief This method performs one step. It transforms the result in-place. Additionally to the other methods * the coordinates, velocities and accelerations are passed directly to do_step and they are transformed out-of-place. * * It can be used like * \code * coordinates qin , qout; * velocities pin , pout; * accelerations ain, aout; * stepper.do_step( sys , qin , pin , ain , qout , pout , aout , t , dt ); * \endcode * * \param system The system function to solve, hence the r.h.s. of the ordinary differential equation. It must fulfill the * Second Order System concept. * \param x The state of the ODE which should be solved. The state is pair of Coor and Velocity. * \param t The value of the time, at which the step should be performed. * \param dt The step size. */ /** * \fn void velocity_verlet::adjust_size( const StateIn &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. */ /** * \fn velocity_verlet::reset( void ) * \brief Resets the internal state of this stepper. After calling this method it is safe to use all * `do_step` method without explicitly initializing the stepper. */ /** * \fn velocity_verlet::initialize( System system , const CoorIn &qin , const VelocityIn &pin , time_type t ) * \brief Initializes the internal state of the stepper. * * This method is equivalent to * \code * Acceleration a; * system( qin , pin , a , t ); * stepper.initialize( a ); * \endcode * * \param system The system function for the next calls of `do_step`. * \param qin The current coordinates of the ODE. * \param pin The current velocities of the ODE. * \param t The current time of the ODE. */ /** * \fn velocity_verlet::is_initialized() * \returns Returns if the stepper is initialized. */ } // namespace odeint } // namespace numeric } // namespace boost #endif // BOOST_NUMERIC_ODEINT_STEPPER_VELOCITY_VERLET_HPP_DEFINED