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/*
* fusion_runge_kutta.hpp
*
* Copyright 2010-2011 Mario Mulansky
* Copyright 2010-2012 Karsten Ahnert
*
* 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 FUSION_EXPLICIT_RK_HPP_
#define FUSION_EXPLICIT_RK_HPP_
#include <boost/mpl/vector.hpp>
#include <boost/mpl/push_back.hpp>
#include <boost/mpl/for_each.hpp>
#include <boost/mpl/range_c.hpp>
#include <boost/mpl/copy.hpp>
#include <boost/mpl/size_t.hpp>
#include <boost/fusion/container.hpp>
#include <boost/fusion/algorithm/iteration.hpp>
#include <boost/array.hpp>
#include "fusion_algebra.hpp"
//#include "fusion_foreach_performance.hpp"
namespace mpl = boost::mpl;
namespace fusion = boost::fusion;
using namespace std;
struct intermediate_stage {};
struct last_stage {};
template< class T , class Constant >
struct array_wrapper
{
typedef const typename boost::array< T , Constant::value > type;
};
template< class T , size_t i , class StageCategory >
struct stage
{
T c;
boost::array< T , i > a;
typedef StageCategory category;
};
template< class T , size_t i>
struct stage< T , i , last_stage >
{
T c;
boost::array< T , i > b;
typedef last_stage category;
};
template< class T , class Constant , class StageCategory >
struct stage_wrapper
{
typedef stage< T , Constant::value , StageCategory > type;
};
template< class StateType , size_t stage_count >
class explicit_rk
{
public:
typedef StateType state_type;
typedef mpl::range_c< size_t , 1 , stage_count > stage_indices;
typedef typename fusion::result_of::as_vector
<
typename mpl::copy
<
stage_indices ,
mpl::inserter
<
mpl::vector0< > ,
mpl::push_back< mpl::_1 , array_wrapper< double , mpl::_2 > >
>
>::type
>::type coef_a_type;
typedef boost::array< double , stage_count > coef_b_type;
typedef boost::array< double , stage_count > coef_c_type;
typedef typename fusion::result_of::as_vector
<
typename mpl::push_back
<
typename mpl::copy
<
stage_indices,
mpl::inserter
<
mpl::vector0<> ,
mpl::push_back< mpl::_1 , stage_wrapper< double , mpl::_2 , intermediate_stage > >
>
>::type ,
stage< double , stage_count , last_stage >
>::type
>::type stage_vector_base;
struct stage_vector : public stage_vector_base
{
struct do_insertion
{
stage_vector_base &m_base;
const coef_a_type &m_a;
const coef_c_type &m_c;
do_insertion( stage_vector_base &base , const coef_a_type &a , const coef_c_type &c )
: m_base( base ) , m_a( a ) , m_c( c ) { }
template< class Index >
void operator()( Index ) const
{
//fusion::at< Index >( m_base ) = stage< double , Index::value+1 , intermediate_stage >( m_c[ Index::value ] , fusion::at< Index >( m_a ) );
fusion::at< Index >( m_base ).c = m_c[ Index::value ];
fusion::at< Index >( m_base ).a = fusion::at< Index >( m_a );
}
};
stage_vector( const coef_a_type &a , const coef_b_type &b , const coef_c_type &c )
{
typedef mpl::range_c< size_t , 0 , stage_count - 1 > indices;
mpl::for_each< indices >( do_insertion( *this , a , c ) );
//fusion::at_c< 0 >( fusion::at_c< stage_count - 1 >( *this ) ) = stage_count - 1 ;
fusion::at_c< stage_count - 1 >( *this ).c = c[ stage_count - 1 ];
fusion::at_c< stage_count - 1 >( *this ).b = b;
}
};
template< class System >
struct calculate_stage
{
System &system;
state_type &x , &x_tmp;
state_type *F;
const double t;
const double dt;
calculate_stage( System &_system , state_type &_x , state_type &_x_tmp , state_type *_F ,
const double _t , const double _dt )
: system( _system ) , x( _x ) , x_tmp( _x_tmp ) , F( _F ) , t( _t ) , dt( _dt )
{}
template< typename T , size_t stage_number >
void inline operator()( stage< T , stage_number , intermediate_stage > const &stage ) const
//typename stage_fusion_wrapper< T , mpl::size_t< stage_number > , intermediate_stage >::type const &stage ) const
{
if( stage_number == 1 )
system( x , F[stage_number-1] , t + stage.c * dt );
else
system( x_tmp , F[stage_number-1] , t + stage.c * dt );
fusion_algebra<stage_number>::foreach( x_tmp , x , stage.a , F , dt);
}
template< typename T , size_t stage_number >
void inline operator()( stage< T , stage_number , last_stage > const &stage ) const
//void operator()( typename stage_fusion_wrapper< T , mpl::size_t< stage_number > , last_stage >::type const &stage ) const
{
if( stage_number == 1 )
system( x , F[stage_number-1] , t + stage.c * dt );
else
system( x_tmp , F[stage_number-1] , t + stage.c * dt );
fusion_algebra<stage_number>::foreach( x , x , stage.b , F , dt);
}
};
public:
explicit_rk( const coef_a_type &a ,
const coef_b_type &b ,
const coef_c_type &c )
: m_stages( a , b , c )
{ }
template< class System >
void inline do_step( System system , state_type &x , const double t , const double dt )
{
fusion::for_each( m_stages , calculate_stage< System >( system , x , m_x_tmp , m_F , t , dt ) );
}
private:
stage_vector m_stages;
state_type m_x_tmp;
protected:
state_type m_F[stage_count];
};
#endif /* FUSION_EXPLICIT_RK_HPP_ */
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