Examples of TestProblem3

org.apache.commons.math.ode.TestProblem3

This class is used in the junit tests for the ODE integrators.

This specific problem is the following differential equation :

 y1'' = -y1/r^3  y1 (0) = 1-e  y1' (0) = 0 y2'' = -y2/r^3  y2 (0) = 0    y2' (0) =sqrt((1+e)/(1-e)) r = sqrt (y1^2 + y2^2), e = 0.9

This is a two-body problem in the plane which can be solved by Kepler's equation

 y1 (t) = ...

org.apache.commons.math3.ode.TestProblem3

This class is used in the junit tests for the ODE integrators.

This specific problem is the following differential equation :

 y1'' = -y1/r^3  y1 (0) = 1-e  y1' (0) = 0 y2'' = -y2/r^3  y2 (0) = 0    y2' (0) =sqrt((1+e)/(1-e)) r = sqrt (y1^2 + y2^2), e = 0.9

This is a two-body problem in the plane which can be solved by Kepler's equation

 y1 (t) = ...

  @Test
  public void testVariableSteps()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {


    final TestProblem3 pb  = new TestProblem3(0.9);
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = scalAbsoluteTolerance;


    FirstOrderIntegrator integ = new DormandPrince853Integrator(minStep, maxStep,
                                                               scalAbsoluteTolerance,
                                                               scalRelativeTolerance);
    integ.addStepHandler(new VariableHandler());
    double stopTime = integ.integrate(pb,
                                      pb.getInitialTime(), pb.getInitialState(),
                                      pb.getFinalTime(), new double[pb.getDimension()]);
    Assert.assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
    Assert.assertEquals("Dormand-Prince 8 (5, 3)", integ.getName());
  }

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Examples of TestProblem3

Examples of org.apache.commons.math3.ode.TestProblem3