Examples of org.apache.commons.math.ode.FirstOrderIntegrator.integrate()

Class org.apache.commons.math.ode.FirstOrderIntegrator

Examples of org.apache.commons.math.ode.FirstOrderIntegrator.integrate()

org.apache.commons.math.ode.FirstOrderIntegrator.integrate()
Integrate the differential equations up to the given time.
This method solves an Initial Value Problem (IVP).

Since this method stores some internal state variables made available in its public interface during integration ( {@link #getCurrentSignedStepsize()}), it is not thread-safe.
@param equations differential equations to integrate @param t0 initial time @param y0 initial value of the state vector at t0 @param t target time for the integration(can be set to a value smaller than t0 for backward integration) @param y placeholder where to put the state vector at each successfulstep (and hence at the end of integration), can be the same object as y0 @throws IntegratorException if the integrator cannot perform integration @throws DerivativeException this exception is propagated to the caller ifthe underlying user function triggers one

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


      FirstOrderIntegrator integ = new ThreeEighthesIntegrator(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() < 5.0e-10);
      assertTrue(handler.getMaximalValueError() < 7.0e-10);
      assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

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


    FirstOrderIntegrator integ = new ThreeEighthesIntegrator(step);
    integ.addStepHandler(new KeplerHandler(pb));
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);
  }


  private static class KeplerHandler implements StepHandler {

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              return false;
          }
          public void reset() {
          }
      });
      integ.integrate(new FirstOrderDifferentialEquations() {
          public void computeDerivatives(double t, double[] y, double[] dot) {
              dot[0] = 1.0;
          }
          public int getDimension() {
              return 1;

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      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              vecAbsoluteTolerance,
                                                              vecRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      fail("an exception should have been thrown");
    } catch(DerivativeException de) {
      fail("wrong exception caught");

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      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              scalAbsoluteTolerance,
                                                              scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);


      // the 1.3 factor is only valid for this test
      // and has been obtained from trial and error

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      FirstOrderIntegrator integ = new HighamHall54Integrator(minStep, maxStep,
                                                              scalAbsoluteTolerance,
                                                              scalRelativeTolerance);
      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() < 5.0e-7);
      assertTrue(handler.getMaximalValueError() < 5.0e-7);
      assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

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    for (int l = 0; l < functions.length; ++l) {
      integ.addEventHandler(functions[l],
                                 Double.POSITIVE_INFINITY, 1.0e-8 * maxStep, 1000);
    }
    assertEquals(functions.length, integ.getEventHandlers().size());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);


    assertTrue(handler.getMaximalValueError() < 1.0e-7);
    assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

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        }
        private static final long serialVersionUID = 935652725339916361L;
      }, Double.POSITIVE_INFINITY, 1.0e-8 * maxStep, 1000);


      try {
        integ.integrate(pb,
                        pb.getInitialTime(), pb.getInitialState(),
                        pb.getFinalTime(), new double[pb.getDimension()]);
        fail("an exception should have been thrown");
      } catch (IntegratorException ie) {
        // expected behavior

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      }
      private static final long serialVersionUID = 935652725339916361L;
    }, Double.POSITIVE_INFINITY, 1.0e-8 * maxStep, 3);


    try {
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      fail("an exception should have been thrown");
    } catch (IntegratorException ie) {
       assertTrue(ie.getCause() != null);

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      double maxStep = pb.getFinalTime() - pb.getInitialTime();


      try {
        FirstOrderIntegrator integ =
            new HighamHall54Integrator(minStep, maxStep, new double[4], new double[4]);
        integ.integrate(pb, pb.getInitialTime(), new double[6],
                        pb.getFinalTime(), new double[pb.getDimension()]);
        fail("an exception should have been thrown");
      } catch (IntegratorException ie) {
        // expected behavior
      }

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