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- /*
- The example how the phase_oscillator ensemble can be implemented using CUDA and thrust
- Copyright 2011-2013 Mario Mulansky
- Copyright 2011 Karsten Ahnert
- 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 <fstream>
- #include <cmath>
- #include <utility>
- #include <thrust/device_vector.h>
- #include <thrust/reduce.h>
- #include <thrust/functional.h>
- #include <boost/numeric/odeint.hpp>
- #include <boost/numeric/odeint/external/thrust/thrust.hpp>
- #include <boost/timer.hpp>
- #include <boost/random/cauchy_distribution.hpp>
- using namespace std;
- using namespace boost::numeric::odeint;
- /*
- * Sorry for that dirty hack, but nvcc has large problems with boost::random.
- *
- * Nevertheless we need the cauchy distribution from boost::random, and therefore
- * we need a generator. Here it is:
- */
- struct drand48_generator
- {
- typedef double result_type;
- result_type operator()( void ) const { return drand48(); }
- result_type min( void ) const { return 0.0; }
- result_type max( void ) const { return 1.0; }
- };
- //[ thrust_phase_ensemble_state_type
- //change this to float if your device does not support double computation
- typedef double value_type;
- //change this to host_vector< ... > of you want to run on CPU
- typedef thrust::device_vector< value_type > state_type;
- // typedef thrust::host_vector< value_type > state_type;
- //]
- //[ thrust_phase_ensemble_mean_field_calculator
- struct mean_field_calculator
- {
- struct sin_functor : public thrust::unary_function< value_type , value_type >
- {
- __host__ __device__
- value_type operator()( value_type x) const
- {
- return sin( x );
- }
- };
- struct cos_functor : public thrust::unary_function< value_type , value_type >
- {
- __host__ __device__
- value_type operator()( value_type x) const
- {
- return cos( x );
- }
- };
- static std::pair< value_type , value_type > get_mean( const state_type &x )
- {
- //[ thrust_phase_ensemble_sin_sum
- value_type sin_sum = thrust::reduce(
- thrust::make_transform_iterator( x.begin() , sin_functor() ) ,
- thrust::make_transform_iterator( x.end() , sin_functor() ) );
- //]
- value_type cos_sum = thrust::reduce(
- thrust::make_transform_iterator( x.begin() , cos_functor() ) ,
- thrust::make_transform_iterator( x.end() , cos_functor() ) );
- cos_sum /= value_type( x.size() );
- sin_sum /= value_type( x.size() );
- value_type K = sqrt( cos_sum * cos_sum + sin_sum * sin_sum );
- value_type Theta = atan2( sin_sum , cos_sum );
- return std::make_pair( K , Theta );
- }
- };
- //]
- //[ thrust_phase_ensemble_sys_function
- class phase_oscillator_ensemble
- {
- public:
- struct sys_functor
- {
- value_type m_K , m_Theta , m_epsilon;
- sys_functor( value_type K , value_type Theta , value_type epsilon )
- : m_K( K ) , m_Theta( Theta ) , m_epsilon( epsilon ) { }
- template< class Tuple >
- __host__ __device__
- void operator()( Tuple t )
- {
- thrust::get<2>(t) = thrust::get<1>(t) + m_epsilon * m_K * sin( m_Theta - thrust::get<0>(t) );
- }
- };
- // ...
- //<-
- phase_oscillator_ensemble( size_t N , value_type g = 1.0 , value_type epsilon = 1.0 )
- : m_omega() , m_N( N ) , m_epsilon( epsilon )
- {
- create_frequencies( g );
- }
- void create_frequencies( value_type g )
- {
- boost::cauchy_distribution< value_type > cauchy( 0.0 , g );
- // boost::variate_generator< boost::mt19937&, boost::cauchy_distribution< value_type > > gen( rng , cauchy );
- drand48_generator d48;
- vector< value_type > omega( m_N );
- for( size_t i=0 ; i<m_N ; ++i )
- omega[i] = cauchy( d48 );
- // generate( omega.begin() , omega.end() , gen );
- m_omega = omega;
- }
- void set_epsilon( value_type epsilon ) { m_epsilon = epsilon; }
- value_type get_epsilon( void ) const { return m_epsilon; }
- //->
- void operator() ( const state_type &x , state_type &dxdt , const value_type dt ) const
- {
- std::pair< value_type , value_type > mean_field = mean_field_calculator::get_mean( x );
- thrust::for_each(
- thrust::make_zip_iterator( thrust::make_tuple( x.begin() , m_omega.begin() , dxdt.begin() ) ),
- thrust::make_zip_iterator( thrust::make_tuple( x.end() , m_omega.end() , dxdt.end()) ) ,
- sys_functor( mean_field.first , mean_field.second , m_epsilon )
- );
- }
- // ...
- //<-
- private:
- state_type m_omega;
- const size_t m_N;
- value_type m_epsilon;
- //->
- };
- //]
- //[ thrust_phase_ensemble_observer
- struct statistics_observer
- {
- value_type m_K_mean;
- size_t m_count;
- statistics_observer( void )
- : m_K_mean( 0.0 ) , m_count( 0 ) { }
- template< class State >
- void operator()( const State &x , value_type t )
- {
- std::pair< value_type , value_type > mean = mean_field_calculator::get_mean( x );
- m_K_mean += mean.first;
- ++m_count;
- }
- value_type get_K_mean( void ) const { return ( m_count != 0 ) ? m_K_mean / value_type( m_count ) : 0.0 ; }
- void reset( void ) { m_K_mean = 0.0; m_count = 0; }
- };
- //]
- // const size_t N = 16384 * 128;
- const size_t N = 16384;
- const value_type pi = 3.1415926535897932384626433832795029;
- const value_type dt = 0.1;
- const value_type d_epsilon = 0.1;
- const value_type epsilon_min = 0.0;
- const value_type epsilon_max = 5.0;
- const value_type t_transients = 10.0;
- const value_type t_max = 100.0;
- int main( int arc , char* argv[] )
- {
- // initial conditions on host
- vector< value_type > x_host( N );
- for( size_t i=0 ; i<N ; ++i ) x_host[i] = 2.0 * pi * drand48();
- //[ thrust_phase_ensemble_system_instance
- phase_oscillator_ensemble ensemble( N , 1.0 );
- //]
- boost::timer timer;
- boost::timer timer_local;
- double dopri5_time = 0.0 , rk4_time = 0.0;
- {
- //[thrust_phase_ensemble_define_dopri5
- typedef runge_kutta_dopri5< state_type , value_type , state_type , value_type > stepper_type;
- //]
- ofstream fout( "phase_ensemble_dopri5.dat" );
- timer.restart();
- for( value_type epsilon = epsilon_min ; epsilon < epsilon_max ; epsilon += d_epsilon )
- {
- ensemble.set_epsilon( epsilon );
- statistics_observer obs;
- state_type x = x_host;
- timer_local.restart();
- // calculate some transients steps
- //[ thrust_phase_ensemble_integration
- size_t steps1 = integrate_const( make_controlled( 1.0e-6 , 1.0e-6 , stepper_type() ) , boost::ref( ensemble ) , x , 0.0 , t_transients , dt );
- //]
- // integrate and compute the statistics
- size_t steps2 = integrate_const( make_dense_output( 1.0e-6 , 1.0e-6 , stepper_type() ) , boost::ref( ensemble ) , x , 0.0 , t_max , dt , boost::ref( obs ) );
- fout << epsilon << "\t" << obs.get_K_mean() << endl;
- cout << "Dopri5 : " << epsilon << "\t" << obs.get_K_mean() << "\t" << timer_local.elapsed() << "\t" << steps1 << "\t" << steps2 << endl;
- }
- dopri5_time = timer.elapsed();
- }
- {
- //[ thrust_phase_ensemble_define_rk4
- typedef runge_kutta4< state_type , value_type , state_type , value_type > stepper_type;
- //]
- ofstream fout( "phase_ensemble_rk4.dat" );
- timer.restart();
- for( value_type epsilon = epsilon_min ; epsilon < epsilon_max ; epsilon += d_epsilon )
- {
- ensemble.set_epsilon( epsilon );
- statistics_observer obs;
- state_type x = x_host;
- timer_local.restart();
- // calculate some transients steps
- size_t steps1 = integrate_const( stepper_type() , boost::ref( ensemble ) , x , 0.0 , t_transients , dt );
- // integrate and compute the statistics
- size_t steps2 = integrate_const( stepper_type() , boost::ref( ensemble ) , x , 0.0 , t_max , dt , boost::ref( obs ) );
- fout << epsilon << "\t" << obs.get_K_mean() << endl;
- cout << "RK4 : " << epsilon << "\t" << obs.get_K_mean() << "\t" << timer_local.elapsed() << "\t" << steps1 << "\t" << steps2 << endl;
- }
- rk4_time = timer.elapsed();
- }
- cout << "Dopri 5 : " << dopri5_time << " s\n";
- cout << "RK4 : " << rk4_time << "\n";
- return 0;
- }
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