public void testModelsMerging() throws DerivativeException, IntegratorException {
// theoretical solution: y[0] = cos(t), y[1] = sin(t)
FirstOrderDifferentialEquations problem =
new FirstOrderDifferentialEquations() {
public void computeDerivatives(double t, double[] y, double[] dot)
throws DerivativeException {
dot[0] = -y[1];
dot[1] = y[0];
}
public int getDimension() {
return 2;
}
};
// integrate backward from π to 0;
ContinuousOutputModel cm1 = new ContinuousOutputModel();
FirstOrderIntegrator integ1 = new DormandPrince853Integrator(0, 1.0, 1.0e-8, 1.0e-8);
integ1.setStepHandler(cm1);
integ1.integrate(problem, Math.PI, new double[] {-1.0, 0.0}, 0, new double[2]);
// integrate backward from 2π to π
ContinuousOutputModel cm2 = new ContinuousOutputModel();
FirstOrderIntegrator integ2 = new DormandPrince853Integrator(0, 0.1, 1.0e-12, 1.0e-12);
integ2.setStepHandler(cm2);
integ2.integrate(problem, 2.0 * Math.PI, new double[] {1.0, 0.0}, Math.PI, new double[2]);
// merge the two half circles
ContinuousOutputModel cm = new ContinuousOutputModel();
cm.append(cm2);
cm.append(new ContinuousOutputModel());
cm.append(cm1);
// check circle
assertEquals(2.0 * Math.PI, cm.getInitialTime(), 1.0e-12);
assertEquals(0, cm.getFinalTime(), 1.0e-12);
assertEquals(cm.getFinalTime(), cm.getInterpolatedTime(), 1.0e-12);
for (double t = 0; t < 2.0 * Math.PI; t += 0.1) {
cm.setInterpolatedTime(t);
double[] y = cm.getInterpolatedState();
assertEquals(Math.cos(t), y[0], 1.0e-7);
assertEquals(Math.sin(t), y[1], 1.0e-7);
}
}
