101 lines
2.4 KiB
C++
101 lines
2.4 KiB
C++
/*
|
|
* bulirsch_stoer.cpp
|
|
*
|
|
* Copyright 2011-2013 Mario Mulansky
|
|
* Copyright 2011-2012 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)
|
|
*/
|
|
|
|
#include <iostream>
|
|
#include <fstream>
|
|
#define _USE_MATH_DEFINES
|
|
#include <cmath>
|
|
|
|
#include <boost/array.hpp>
|
|
#include <boost/ref.hpp>
|
|
|
|
#include <boost/numeric/odeint/config.hpp>
|
|
|
|
#include <boost/numeric/odeint.hpp>
|
|
#include <boost/numeric/odeint/stepper/bulirsch_stoer.hpp>
|
|
#include <boost/numeric/odeint/stepper/bulirsch_stoer_dense_out.hpp>
|
|
|
|
using namespace std;
|
|
using namespace boost::numeric::odeint;
|
|
|
|
typedef boost::array< double , 1 > state_type;
|
|
|
|
/*
|
|
* x' = ( - x*sin t + 2 tan x ) y
|
|
* with x( pi/6 ) = 2/sqrt(3) the analytic solution is 1/cos t
|
|
*/
|
|
|
|
void rhs( const state_type &x , state_type &dxdt , const double t )
|
|
{
|
|
dxdt[0] = ( - x[0] * sin( t ) + 2.0 * tan( t ) ) * x[0];
|
|
}
|
|
|
|
void rhs2( const state_type &x , state_type &dxdt , const double t )
|
|
{
|
|
dxdt[0] = sin(t);
|
|
}
|
|
|
|
|
|
ofstream out;
|
|
|
|
void write_out( const state_type &x , const double t )
|
|
{
|
|
out << t << '\t' << x[0] << endl;
|
|
}
|
|
|
|
int main()
|
|
{
|
|
bulirsch_stoer_dense_out< state_type > stepper( 1E-8 , 0.0 , 0.0 , 0.0 );
|
|
bulirsch_stoer< state_type > stepper2( 1E-8 , 0.0 , 0.0 , 0.0 );
|
|
|
|
state_type x = {{ 2.0 / sqrt(3.0) }};
|
|
|
|
double t = M_PI/6.0;
|
|
//double t = 0.0;
|
|
double dt = 0.01;
|
|
double t_end = M_PI/2.0 - 0.1;
|
|
//double t_end = 100.0;
|
|
|
|
out.open( "bs.dat" );
|
|
out.precision(16);
|
|
integrate_const( stepper , rhs , x , t , t_end , dt , write_out );
|
|
out.close();
|
|
|
|
x[0] = 2.0 / sqrt(3.0);
|
|
|
|
out.open( "bs2.dat" );
|
|
out.precision(16);
|
|
integrate_adaptive( stepper , rhs , x , t , t_end , dt , write_out );
|
|
out.close();
|
|
|
|
x[0] = 2.0 / sqrt(3.0);
|
|
|
|
out.open( "bs3.dat" );
|
|
out.precision(16);
|
|
integrate_adaptive( stepper2 , rhs , x , t , t_end , dt , write_out );
|
|
out.close();
|
|
|
|
|
|
typedef runge_kutta_dopri5< state_type > dopri5_type;
|
|
typedef controlled_runge_kutta< dopri5_type > controlled_dopri5_type;
|
|
typedef dense_output_runge_kutta< controlled_dopri5_type > dense_output_dopri5_type;
|
|
|
|
dense_output_dopri5_type dopri5 = make_dense_output( 1E-9 , 1E-9 , dopri5_type() );
|
|
|
|
x[0] = 2.0 / sqrt(3.0);
|
|
|
|
out.open( "bs4.dat" );
|
|
out.precision(16);
|
|
integrate_adaptive( dopri5 , rhs , x , t , t_end , dt , write_out );
|
|
out.close();
|
|
|
|
}
|