Examples of org.apache.commons.math.ode.GillIntegrator

org.apache.commons.math.ode.GillIntegrator
This class implements the Gill fourth order Runge-Kutta integrator for Ordinary Differential Equations .
This method is an explicit Runge-Kutta method, its Butcher-array is the following one :
```
 0  |    0        0       0      0 1/2 |   1/2       0       0      0 1/2 | (q-1)/2  (2-q)/2    0      0 1  |    0       -q/2  (2+q)/2   0 |------------------------------- |   1/6    (2-q)/6 (2+q)/6  1/6 
```
where q = sqrt(2)
@see EulerIntegrator @see ClassicalRungeKuttaIntegrator @see MidpointIntegrator @see ThreeEighthesIntegrator @version $Revision: 620312 $ $Date: 2008-02-10 12:28:59 -0700 (Sun, 10 Feb 2008) $ @since 1.2

    throws DerivativeException, IntegratorException,
           IOException, ClassNotFoundException {


    TestProblem3 pb = new TestProblem3(0.9);
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.0003;
    GillIntegrator integ = new GillIntegrator(step);
    integ.setStepHandler(new ContinuousOutputModel());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ObjectOutputStream    oos = new ObjectOutputStream(bos);
    oos.writeObject(integ.getStepHandler());


    assertTrue(bos.size () > 700000);
    assertTrue(bos.size () < 701000);


    ByteArrayInputStream  bis = new ByteArrayInputStream(bos.toByteArray());

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  }


  public void testDimensionCheck() {
    try  {
      TestProblem1 pb = new TestProblem1();
      new GillIntegrator(0.01).integrate(pb,
                                         0.0, new double[pb.getDimension()+10],
                                         1.0, new double[pb.getDimension()+10]);
        fail("an exception should have been thrown");
    } catch(DerivativeException de) {
      fail("wrong exception caught");

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        TestProblemAbstract pb = (TestProblemAbstract) problems[k].clone();
        double step = (pb.getFinalTime() - pb.getInitialTime())
          * Math.pow(2.0, -i);


        FirstOrderIntegrator integ = new GillIntegrator(step);
        TestProblemHandler handler = new TestProblemHandler(pb, integ);
        integ.setStepHandler(handler);
        SwitchingFunction[] functions = pb.getSwitchingFunctions();
        for (int l = 0; l < functions.length; ++l) {
          integ.addSwitchingFunction(functions[l],
                                     Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
        }
        integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                        pb.getFinalTime(), new double[pb.getDimension()]);


        double error = handler.getMaximalValueError();
        if (i > 5) {
          assertTrue(error < Math.abs(previousError));

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    throws DerivativeException, IntegratorException {


    TestProblem1 pb = new TestProblem1();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;


    FirstOrderIntegrator integ = new GillIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.setStepHandler(handler);
    integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    assertTrue(handler.getLastError() < 2.0e-13);
    assertTrue(handler.getMaximalValueError() < 4.0e-12);
    assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
    assertEquals("Gill", integ.getName());


  }

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    throws DerivativeException, IntegratorException {


    TestProblem1 pb = new TestProblem1();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.2;


    FirstOrderIntegrator integ = new GillIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.setStepHandler(handler);
    integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    assertTrue(handler.getLastError() > 0.0004);
    assertTrue(handler.getMaximalValueError() > 0.005);
    assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

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    throws DerivativeException, IntegratorException {


    final TestProblem3 pb  = new TestProblem3(0.9);
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.0003;


    FirstOrderIntegrator integ = new GillIntegrator(step);
    integ.setStepHandler(new KeplerStepHandler(pb));
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);
  }

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  }


  public void testUnstableDerivative()
  throws DerivativeException, IntegratorException {
    final StepProblem stepProblem = new StepProblem(0.0, 1.0, 2.0);
    FirstOrderIntegrator integ = new GillIntegrator(0.3);
    integ.addSwitchingFunction(stepProblem, 1.0, 1.0e-12, 1000);
    double[] y = { Double.NaN };
    integ.integrate(stepProblem, 0.0, new double[] { 0.0 }, 10.0, y);
    assertEquals(8.0, y[0], 1.0e-12);
  }

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Related Classes of org.apache.commons.math.ode.GillIntegrator

org.apache.commons.math.ode.GillIntegratorTest

org.apache.commons.math.ode.GillStepInterpolatorTest

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