58 lines
1.9 KiB
C++
58 lines
1.9 KiB
C++
#include "api.hpp"
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#include "state.hpp"
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#include <cstddef>
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PLUGIN_EXPORT std::uint32_t plugin_api_version(){
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return PLUGIN_API_VERSION;
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}
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PLUGIN_EXPORT PluginType plugin_type(){
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return PluginType::Solver;
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}
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PLUGIN_EXPORT const char* plugin_name(){
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return "Adams-Bashforth 2";
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}
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PLUGIN_EXPORT const char* plugin_description(){
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return "Explicit second-order Adams-Bashforth method with an RK4 start";
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}
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PLUGIN_EXPORT void transform(const SolverParameters* parameters,
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SolutionPoint* output,
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size_t output_size){
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if (parameters == nullptr || output == nullptr || output_size == 0)
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return;
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const State initial_state{1.0, 0.0, 0.0};
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output[0] = make_step(parameters->t_begin, initial_state);
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if (output_size == 1)
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return;
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State first_state = runge_kutta_step(initial_state, *parameters);
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output[1] = make_step(parameters->t_begin + parameters->step, first_state);
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for (size_t index = 1; index + 1 < output_size; ++index){
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State current = state_from_point(output[index]);
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State previous = state_from_point(output[index - 1]);
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State current_derivative = derivative(current, *parameters);
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State previous_derivative = derivative(previous, *parameters);
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double h = parameters->step;
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State next{
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current.x1 + h * (1.5 * current_derivative.x1 -
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0.5 * previous_derivative.x1),
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current.x2 + h * (1.5 * current_derivative.x2 -
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0.5 * previous_derivative.x2),
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current.x3 + h * (1.5 * current_derivative.x3 -
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0.5 * previous_derivative.x3),
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};
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const double next_time = parameters->t_begin +
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static_cast<double>(index + 1) * h;
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output[index + 1] = make_step(next_time, next);
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}
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}
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