80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
/* Boost libs/numeric/odeint/examples/openmp/lorenz_ensemble_simple.cpp
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Copyright 2013 Karsten Ahnert
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Copyright 2013 Mario Mulansky
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Copyright 2013 Pascal Germroth
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Parallelized Lorenz ensembles
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or
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copy at http://www.boost.org/LICENSE_1_0.txt)
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*/
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#include <omp.h>
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#include <vector>
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#include <iostream>
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#include <boost/numeric/odeint.hpp>
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#include <boost/numeric/odeint/external/openmp/openmp.hpp>
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#include "point_type.hpp"
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using namespace std;
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typedef vector<double> vector_type;
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typedef point<double, 3> point_type;
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typedef vector<point_type> state_type;
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const double sigma = 10.0;
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const double b = 8.0 / 3.0;
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struct sys_func {
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const vector_type &R;
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sys_func( const vector_type &_R ) : R( _R ) { }
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void operator()( const state_type &x , state_type &dxdt , double t ) const {
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const size_t n = x.size();
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# pragma omp parallel for
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for(size_t i = 0 ; i < n ; i++) {
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const point_type &xi = x[i];
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point_type &dxdti = dxdt[i];
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dxdti[0] = -sigma * (xi[0] - xi[1]);
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dxdti[1] = R[i] * xi[0] - xi[1] - xi[0] * xi[2];
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dxdti[2] = -b * xi[2] + xi[0] * xi[1];
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}
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}
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};
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int main() {
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using namespace boost::numeric::odeint;
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const size_t n = 1024;
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vector_type R(n);
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const double Rmin = 0.1, Rmax = 50.0;
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# pragma omp parallel for
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for(size_t i = 0 ; i < n ; i++)
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R[i] = Rmin + (Rmax - Rmin) / (n - 1) * i;
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state_type X(n, point_type(10, 10, 10));
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const double t_max = 10.0, dt = 0.01;
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// Simple stepper with constant step size
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// typedef runge_kutta4<state_type, double, state_type, double,
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// openmp_range_algebra> stepper;
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// integrate_const(stepper(), sys_func(R), X, 0.0, t_max, dt);
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// Controlled stepper with variable step size
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typedef runge_kutta_fehlberg78<state_type, double, state_type, double,
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openmp_range_algebra> error_stepper_type;
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typedef controlled_runge_kutta<error_stepper_type> controlled_stepper_type;
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controlled_stepper_type controlled_stepper;
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integrate_adaptive(controlled_stepper, sys_func(R), X, 0.0, t_max, dt);
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copy( X.begin(), X.end(), ostream_iterator<point_type>(cout, "\n") );
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return 0;
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}
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