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126 lines
3.0 KiB
C++
126 lines
3.0 KiB
C++
/*
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* Simulation of an ensemble of Roessler attractors
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*
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* Copyright 2014 Mario Mulansky
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*
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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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*/
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#include <iostream>
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#include <vector>
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#include <random>
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#include <boost/timer.hpp>
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#include <boost/array.hpp>
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#include <boost/numeric/odeint.hpp>
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namespace odeint = boost::numeric::odeint;
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typedef boost::timer timer_type;
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typedef double fp_type;
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//typedef float fp_type;
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typedef boost::array<fp_type, 3> state_type;
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typedef std::vector<state_type> state_vec;
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//---------------------------------------------------------------------------
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struct roessler_system {
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const fp_type m_a, m_b, m_c;
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roessler_system(const fp_type a, const fp_type b, const fp_type c)
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: m_a(a), m_b(b), m_c(c)
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{}
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void operator()(const state_type &x, state_type &dxdt, const fp_type t) const
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{
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dxdt[0] = -x[1] - x[2];
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dxdt[1] = x[0] + m_a * x[1];
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dxdt[2] = m_b + x[2] * (x[0] - m_c);
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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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if(argc<3)
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{
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std::cerr << "Expected size and steps as parameter" << std::endl;
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exit(1);
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}
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const size_t n = atoi(argv[1]);
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const size_t steps = atoi(argv[2]);
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//const size_t steps = 50;
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const fp_type dt = 0.01;
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const fp_type a = 0.2;
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const fp_type b = 1.0;
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const fp_type c = 9.0;
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// random initial conditions on the device
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std::vector<fp_type> x(n), y(n), z(n);
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std::default_random_engine generator;
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std::uniform_real_distribution<fp_type> distribution_xy(-8.0, 8.0);
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std::uniform_real_distribution<fp_type> distribution_z(0.0, 20.0);
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auto rand_xy = std::bind(distribution_xy, std::ref(generator));
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auto rand_z = std::bind(distribution_z, std::ref(generator));
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std::generate(x.begin(), x.end(), rand_xy);
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std::generate(y.begin(), y.end(), rand_xy);
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std::generate(z.begin(), z.end(), rand_z);
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state_vec state(n);
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for(size_t i=0; i<n; ++i)
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{
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state[i][0] = x[i];
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state[i][1] = y[i];
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state[i][2] = z[i];
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}
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std::cout.precision(16);
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std::cout << "# n: " << n << std::endl;
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std::cout << x[0] << std::endl;
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// Stepper type - use never_resizer for slight performance improvement
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odeint::runge_kutta4_classic<state_type, fp_type, state_type, fp_type,
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odeint::array_algebra,
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odeint::default_operations,
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odeint::never_resizer> stepper;
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roessler_system sys(a, b, c);
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timer_type timer;
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fp_type t = 0.0;
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for (int step = 0; step < steps; step++)
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{
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for(size_t i=0; i<n; ++i)
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{
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stepper.do_step(sys, state[i], t, dt);
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}
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t += dt;
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}
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std::cout << "Integration finished, runtime for " << steps << " steps: ";
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std::cout << timer.elapsed() << " s" << std::endl;
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// compute some accumulation to make sure all results have been computed
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fp_type s = 0.0;
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for(size_t i = 0; i < n; ++i)
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{
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s += state[i][0];
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}
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std::cout << state[0][0] << std::endl;
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std::cout << s/n << std::endl;
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}
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