92 lines
2.4 KiB
C++
92 lines
2.4 KiB
C++
/* Boost libs/numeric/odeint/examples/openmp/lorenz_ensemble.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 <iterator>
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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 <boost/lexical_cast.hpp>
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#include "point_type.hpp"
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using namespace std;
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using namespace boost::numeric::odeint;
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typedef point<double, 3> point_type;
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typedef vector< point_type > inner_state_type;
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typedef openmp_state<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<double> &R;
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sys_func( vector<double> &R ) : R(R) {}
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void operator()( const state_type &x , state_type &dxdt , double t ) const {
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# pragma omp parallel for
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for(size_t j = 0 ; j < x.size() ; j++) {
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size_t offset = 0;
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for(size_t i = 0 ; i < j ; i++)
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offset += x[i].size();
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for(size_t i = 0 ; i < x[j].size() ; i++) {
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const point_type &xi = x[j][i];
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point_type &dxdti = dxdt[j][i];
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dxdti[0] = -sigma * (xi[0] - xi[1]);
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dxdti[1] = R[offset + 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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};
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int main(int argc, char **argv) {
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size_t n = 1024;
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if(argc > 1) n = boost::lexical_cast<size_t>(argv[1]);
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vector<double> 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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vector<point_type> inner(n, point_type(10, 10, 10));
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state_type state;
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split(inner, state);
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cerr << "openmp_state split " << n << " into";
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for(size_t i = 0 ; i != state.size() ; i++)
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cerr << ' ' << state[i].size();
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cerr << endl;
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typedef runge_kutta4< state_type, double > stepper;
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const double t_max = 10.0, dt = 0.01;
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integrate_const(
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stepper(),
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sys_func(R),
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state,
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0.0, t_max, dt
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);
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unsplit(state, inner);
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std::copy( inner.begin(), inner.end(), ostream_iterator<point_type>(cout, "\n") );
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return 0;
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}
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