Package org.apache.commons.math.ode.nonstiff

Examples of org.apache.commons.math.ode.nonstiff.EulerIntegrator


  }

  public void testStepSize()
    throws DerivativeException, IntegratorException {
      final double step = 1.23456;
      FirstOrderIntegrator integ = new EulerIntegrator(step);
      integ.addStepHandler(new StepHandler() {
        public void handleStep(StepInterpolator interpolator, boolean isLast) {
            if (! isLast) {
                assertEquals(step,
                             interpolator.getCurrentTime() - interpolator.getPreviousTime(),
                             1.0e-12);
            }
        }
        public boolean requiresDenseOutput() {
            return false;
        }
        public void reset() {
        }
      });
      integ.integrate(new FirstOrderDifferentialEquations() {
                          private static final long serialVersionUID = 0L;
                          public void computeDerivatives(double t, double[] y, double[] dot) {
                              dot[0] = 1.0;
                          }
                          public int getDimension() {
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  }

  public void testDimensionCheck() {
    try  {
      TestProblem1 pb = new TestProblem1();
      new EulerIntegrator(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  = problems[k].copy();
        double step = (pb.getFinalTime() - pb.getInitialTime())
          * Math.pow(2.0, -i);

        FirstOrderIntegrator integ = new EulerIntegrator(step);
        TestProblemHandler handler = new TestProblemHandler(pb, integ);
        integ.addStepHandler(handler);
        EventHandler[] functions = pb.getEventsHandlers();
        for (int l = 0; l < functions.length; ++l) {
          integ.addEventHandler(functions[l],
                                     Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
        }
        double stopTime = integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                                          pb.getFinalTime(), new double[pb.getDimension()]);
        if (functions.length == 0) {
            assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
        }

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    throws DerivativeException, IntegratorException {

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

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

   assertTrue(handler.getLastError() < 2.0e-4);
   assertTrue(handler.getMaximalValueError() < 1.0e-3);
   assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
   assertEquals("Euler", integ.getName());

  }
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    throws DerivativeException, IntegratorException {

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

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

    assertTrue(handler.getLastError() > 0.01);
    assertTrue(handler.getMaximalValueError() > 0.2);
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      throws DerivativeException, IntegratorException {

      TestProblem5 pb = new TestProblem5();
      double step = Math.abs(pb.getFinalTime() - pb.getInitialTime()) * 0.001;

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

      assertTrue(handler.getLastError() < 0.45);
      assertTrue(handler.getMaximalValueError() < 0.45);
      assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
      assertEquals("Euler", integ.getName());
  }
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  }

  public void testDimensionCheck() {
    try  {
      TestProblem1 pb = new TestProblem1();
      new EulerIntegrator(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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      for (int i = 4; i < 8; ++i) {

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

        FirstOrderIntegrator integ = new EulerIntegrator(step);
        TestProblemHandler handler = new TestProblemHandler(pb, integ);
        integ.addStepHandler(handler);
        EventHandler[] functions = pb.getEventsHandlers();
        for (int l = 0; l < functions.length; ++l) {
          integ.addEventHandler(functions[l],
                                     Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
        }
        double stopTime = integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                                          pb.getFinalTime(), new double[pb.getDimension()]);
        if (functions.length == 0) {
            assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
        }

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    throws DerivativeException, IntegratorException {

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

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

   assertTrue(handler.getLastError() < 2.0e-4);
   assertTrue(handler.getMaximalValueError() < 1.0e-3);
   assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
   assertEquals("Euler", integ.getName());

  }
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    throws DerivativeException, IntegratorException {

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

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

    assertTrue(handler.getLastError() > 0.01);
    assertTrue(handler.getMaximalValueError() > 0.2);
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