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