rungekuttadiffeqsolver.java

来自「一个一元曲线多项式数值演示例子」· Java 代码 · 共 33 行

package numbercruncher.mathutils;

/**
 * Differential equation solver that implements
 * a fourth-order Runge-Kutta algorithm.
 */
public class RungeKuttaDiffEqSolver
    extends DiffEqSolver {
  /**
   * Constructor.
   * @param equation the differential equation to solve
   */
  public RungeKuttaDiffEqSolver(DifferentialEquation equation) {
    super(equation);
  }

  /**
   * Return the next data point in the
   * approximation of the solution.
   * @param h the width of the interval
   */
  public DataPoint nextPoint(float h) {
    float k1 = equation.at(x, y);
    float k2 = equation.at(x + h / 2, y + k1 * h / 2);
    float k3 = equation.at(x + h / 2, y + k2 * h / 2);
    float k4 = equation.at(x + h, y + k3 * h);

    y += (k1 + 2 * (k2 + k3) + k4) * h / 6;
    x += h;

    return new DataPoint(x, y);
  }
}