Squashed 'third_party/boostorg/odeint/' content from commit 6ff2719
Change-Id: If4892e29c1a5e6cf3a7aa51486a2725c251b0c7d
git-subtree-dir: third_party/boostorg/odeint
git-subtree-split: 6ff2719b6907b86596c3d43e88c1bcfdf29df560
diff --git a/examples/mpi/phase_chain.cpp b/examples/mpi/phase_chain.cpp
new file mode 100644
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+++ b/examples/mpi/phase_chain.cpp
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+/*
+ * phase_chain.cpp
+ *
+ * Example of MPI 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_mpi_header
+#include <boost/numeric/odeint.hpp>
+#include <boost/numeric/odeint/external/mpi/mpi.hpp>
+//]
+
+using namespace std;
+using namespace boost::numeric::odeint;
+using boost::timer::cpu_timer;
+using boost::math::double_constants::pi;
+
+//[phase_chain_state
+typedef mpi_state< vector<double> > state_type;
+//]
+
+//[phase_chain_mpi_rhs
+struct phase_chain_mpi_state
+{
+ phase_chain_mpi_state( double gamma = 0.5 )
+ : m_gamma( gamma ) { }
+
+ void operator()( const state_type &x , state_type &dxdt , double /* t */ ) const
+ {
+ const size_t M = x().size();
+ const bool have_left = x.world.rank() > 0,
+ have_right = x.world.rank() < x.world.size()-1;
+ double x_left, x_right;
+ boost::mpi::request r_left, r_right;
+ if( have_left )
+ {
+ x.world.isend( x.world.rank()-1 , 0 , x().front() ); // send to x_right
+ r_left = x.world.irecv( x.world.rank()-1 , 0 , x_left ); // receive from x().back()
+ }
+ if( have_right )
+ {
+ x.world.isend( x.world.rank()+1 , 0 , x().back() ); // send to x_left
+ r_right = x.world.irecv( x.world.rank()+1 , 0 , x_right ); // receive from x().front()
+ }
+ for(size_t m = 1 ; m < M-1 ; ++m)
+ {
+ dxdt()[m] = coupling_func( x()[m+1] - x()[m] ) +
+ coupling_func( x()[m-1] - x()[m] );
+ }
+ dxdt()[0] = coupling_func( x()[1] - x()[0] );
+ if( have_left )
+ {
+ r_left.wait();
+ dxdt()[0] += coupling_func( x_left - x().front() );
+ }
+ dxdt()[M-1] = coupling_func( x()[M-2] - x()[M-1] );
+ if( have_right )
+ {
+ r_right.wait();
+ dxdt()[M-1] += coupling_func( x_right - x().back() );
+ }
+ }
+
+ 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_mpi_init
+ boost::mpi::environment env( argc , argv );
+ boost::mpi::communicator world;
+
+ const size_t N = 131101;
+ vector<double> x;
+ if( world.rank() == 0 )
+ {
+ x.resize( 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 ) );
+ }
+
+ state_type x_split( world );
+ split( x , x_split );
+ //]
+
+
+ cpu_timer timer;
+ //[phase_chain_mpi_integrate
+ integrate_n_steps( runge_kutta4<state_type>() , phase_chain_mpi_state( 1.2 ) ,
+ x_split , 0.0 , 0.01 , 100 );
+ unsplit( x_split , x );
+ //]
+
+ if( world.rank() == 0 )
+ {
+ 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;
+}