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//
//
// chaos~
// Copyright (C) 2004 Tim Blechmann
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING. If not, write to
// the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA 02111-1307, USA.
#include "ode_base.hpp"
void ode_base::rk1()
{
m_system (m_k[0], m_data);
for (int i = 0; i != m_num_eq; ++i)
m_data[i] += m_dt * m_k[0][i];
}
void ode_base::rk2()
{
m_system (m_k[0], m_data);
for (int i = 0; i != m_num_eq; ++i)
m_k[0][i] = m_k[0][i] * 0.5 * m_dt + m_data[i];
m_system (m_k[1], m_k[0]);
for (int i = 0; i != m_num_eq; ++i)
m_data[i] += m_dt * m_k[1][i];
}
void ode_base::rk4()
{
m_system (m_k[0], m_data);
for (int i = 0; i != m_num_eq; ++i)
{
m_k[0][i] *= m_dt;
m_tmp[i] = m_data[i] + 0.5 * m_k[0][i];
}
m_system (m_k[1], m_tmp);
for (int i = 0; i != m_num_eq; ++i)
{
m_k[1][i] *= m_dt;
m_tmp[i] = m_data[i] + 0.5 * m_k[1][i];
}
m_system (m_k[2], m_tmp);
for (int i = 0; i != m_num_eq; ++i)
{
m_k[2][i] *= m_dt;
m_tmp[i] = m_data[i] + m_k[2][i];
}
m_system (m_k[3], m_tmp);
for (int i = 0; i != m_num_eq; ++i)
m_k[3][i] *= m_dt;
for (int i = 0; i != m_num_eq; ++i)
m_data[i] += (m_k[0][i] + 2. * (m_k[1][i] + m_k[2][i]) + m_k[3][i])
/ 6.;
}
void ode_base::m_step()
{
switch (m_method)
{
case 0:
rk1();
break;
case 1:
rk2();
break;
case 2:
rk4();
break;
}
}
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