Namespace

Make a shorter namespace alias.

namespace odeint = boost::numeric::odeint;

Integrate

The process of running differential equations.

odeint::integrate_const(stepper, math_system, init_state, t0, t1, dt, observer);

Steppers

Runge-Kutta 4 (rk4) is the most accurate and fast stepper.

odeint::runge_kutta4<state_type> rk4;

System of Equations

The mathematical system of equations.

void sytem(x, dxdt, t0;

Observer

Observer is called at each time step.

void observer(x, t);

c++ example

#include <boost/numeric/odeint.hpp>
#include <functional>
#include <vector>
#include <iostream>

namespace odeint = boost::numeric::odeint;

namespace nsb
{
	using std::placeholders::_1;
	using std::placeholders::_2;
	using std::placeholders::_3;
	using std::placeholders::_4;
	using std::placeholders::_5;
}

namespace nsb
{
	using dfloat = float;
	using state_type = std::vector<dfloat>;

	class equation
	{
	public:
		void system(const nsb::state_type & x, nsb::state_type & dxdt, const nsb::dfloat time) const
		{
			dxdt[0] = x[0] - x[1] + x[2];
			dxdt[1] = 2*x[0] + x[1] - 2*x[2];
			dxdt[2] = -x[0] + 3*x[1] - x[2];
		}
		void observer(const nsb::state_type & x, const dfloat time) const
		{
			std::cout << time << "	=>	" << x[0] << "	" << x[1] << "	" << x[2] << std::endl;
		}
	public:
		void run() const
		{
			nsb::state_type init{0.1, 0.7, 0.9};
			odeint::integrate_const(
				odeint::runge_kutta4<nsb::state_type>{},
				std::bind(
					&nsb::equation::system,
					this,
					_1,
					_2,
					_3
				),
				init,
				nsb::dfloat{0},
				nsb::dfloat{25},
				nsb::dfloat{0.1},
				std::bind(
					&nsb::equation::observer,
					this,
					_1,
					_2
				)
			);
		}
	};
}

int main()
{
	nsb::equation eqt;
	eqt.run();
}

Date

Sat Jun 7 05:22:11 AM UTC 2025

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