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fix initialization with external stepper (#215)

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- time was not increased over the iterations
- prediction of dxdt was taken before integrating with the supplied stepper instead of after
This commit is contained in:
Valentin Hartmann 2017-11-12 21:12:17 +01:00 committed by Mario Mulansky
parent 540f46f42c
commit 34def567d2
2 changed files with 16 additions and 11 deletions
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20
include/boost/numeric/odeint/stepper/adaptive_adams_bashforth_moulton.hpp
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@ -110,16 +110,23 @@ public:
template< class ExplicitStepper, class System >
void initialize(ExplicitStepper stepper, System system, state_type &inOut, time_type &t, time_type dt)
{
reset();
dt = dt/static_cast< time_type >(order_value);
m_dxdt_resizer.adjust_size( inOut , detail::bind( &stepper_type::template resize_dxdt_impl< state_type > , detail::ref( *this ) , detail::_1 ) );
system( inOut , m_dxdt.m_v , t );
for( size_t i=0 ; i<order_value; ++i )
{
system( inOut , m_dxdt.m_v , t );
stepper.do_step_dxdt_impl( system, inOut, m_dxdt.m_v, t, dt/static_cast< Time >(order_value) );
stepper.do_step_dxdt_impl( system, inOut, m_dxdt.m_v, t, dt );
m_coeff.predict(t, dt/static_cast< Time >(order_value));
system( inOut , m_dxdt.m_v , t + dt);
m_coeff.predict(t, dt);
m_coeff.do_step(m_dxdt.m_v);
m_coeff.confirm();
t += dt;
if(m_coeff.m_eo < order_value)
{
@ -131,10 +138,13 @@ public:
template< class System >
void initialize(System system, state_type &inOut, time_type &t, time_type dt)
{
reset();
dt = dt/static_cast< time_type >(order_value);
for(size_t i=0; i<order_value; ++i)
{
this->do_step(system, inOut, t, dt/static_cast< Time >(order_value));
t += dt/static_cast< Time >(order_value);
this->do_step(system, inOut, t, dt);
t += dt;
};
};

7
test/numeric/adaptive_adams_bashforth_moulton.cpp
View File

@ -68,12 +68,7 @@ struct perform_adaptive_adams_bashforth_moulton_test
stepper.initialize( init_stepper, osc() , x1 , t , dt);
double A = std::sqrt( x1[0]*x1[0] + x1[1]*x1[1] );
double phi = std::asin(x1[0]/A) - t;
// more steps necessary to "counteract" the effect from the lower order steps
for( size_t n=0 ; n < stepper.steps ; ++n )
{
stepper.do_step( osc() , x1 , t , dt );
t += dt;
}
// now we do the actual step
stepper.do_step( osc() , x1 , t , dt );
// only examine the error of the adams-bashforth step, not the initialization