| /* |
| * phase_chain.cpp |
| * |
| * Example of OMP parallelization with odeint |
| * |
| * Copyright 2013 Karsten Ahnert |
| * Copyright 2013 Mario Mulansky |
| * Copyright 2013 Pascal Germroth |
| * 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 <vector> |
| #include <boost/random.hpp> |
| #include <boost/timer/timer.hpp> |
| //[phase_chain_openmp_header |
| #include <omp.h> |
| #include <boost/numeric/odeint.hpp> |
| #include <boost/numeric/odeint/external/openmp/openmp.hpp> |
| //] |
| |
| using namespace std; |
| using namespace boost::numeric::odeint; |
| using boost::timer::cpu_timer; |
| using boost::math::double_constants::pi; |
| |
| //[phase_chain_vector_state |
| typedef std::vector< double > state_type; |
| //] |
| |
| //[phase_chain_rhs |
| struct phase_chain |
| { |
| phase_chain( double gamma = 0.5 ) |
| : m_gamma( gamma ) { } |
| |
| void operator()( const state_type &x , state_type &dxdt , double /* t */ ) const |
| { |
| const size_t N = x.size(); |
| #pragma omp parallel for schedule(runtime) |
| for(size_t i = 1 ; i < N - 1 ; ++i) |
| { |
| dxdt[i] = coupling_func( x[i+1] - x[i] ) + |
| coupling_func( x[i-1] - x[i] ); |
| } |
| dxdt[0 ] = coupling_func( x[1 ] - x[0 ] ); |
| dxdt[N-1] = coupling_func( x[N-2] - x[N-1] ); |
| } |
| |
| double coupling_func( double x ) const |
| { |
| return sin( x ) - m_gamma * ( 1.0 - cos( x ) ); |
| } |
| |
| double m_gamma; |
| }; |
| //] |
| |
| |
| int main( int argc , char **argv ) |
| { |
| //[phase_chain_init |
| size_t N = 131101; |
| state_type x( N ); |
| boost::random::uniform_real_distribution<double> distribution( 0.0 , 2.0*pi ); |
| boost::random::mt19937 engine( 0 ); |
| generate( x.begin() , x.end() , boost::bind( distribution , engine ) ); |
| //] |
| |
| //[phase_chain_stepper |
| typedef runge_kutta4< |
| state_type , double , |
| state_type , double , |
| openmp_range_algebra |
| > stepper_type; |
| //] |
| |
| //[phase_chain_scheduling |
| int chunk_size = N/omp_get_max_threads(); |
| omp_set_schedule( omp_sched_static , chunk_size ); |
| //] |
| |
| cpu_timer timer; |
| //[phase_chain_integrate |
| integrate_n_steps( stepper_type() , phase_chain( 1.2 ) , |
| x , 0.0 , 0.01 , 100 ); |
| //] |
| double run_time = static_cast<double>(timer.elapsed().wall) * 1.0e-9; |
| std::cerr << run_time << "s" << std::endl; |
| // copy(x.begin(), x.end(), ostream_iterator<double>(cout, "\n")); |
| |
| return 0; |
| } |