org.apache.commons.math.ode
Class TestProblem3

java.lang.Object
  org.apache.commons.math.ode.TestProblemAbstract
      org.apache.commons.math.ode.TestProblem3

All Implemented Interfaces:

org.apache.commons.math.ode.FirstOrderDifferentialEquations

public class TestProblem3
extends TestProblemAbstract

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) = ...
 

Field Summary

Fields inherited from class org.apache.commons.math.ode.TestProblemAbstract

calls, errorScale, n, t0, t1, y0

Constructor Summary

TestProblem3()
Simple constructor.

TestProblem3(double e)
Simple constructor.

TestProblem3(TestProblem3 problem)
Copy constructor.

Method Summary

double[]	computeTheoreticalState(double t) Compute the theoretical state at the specified time.
TestProblem3	copy() Copy operation.
void	doComputeDerivatives(double t, double[] y, double[] yDot)

Methods inherited from class org.apache.commons.math.ode.TestProblemAbstract

computeDerivatives, getCalls, getDimension, getErrorScale, getEventsHandlers, getFinalTime, getInitialState, getInitialTime, setErrorScale, setFinalConditions, setInitialConditions

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TestProblem3

public TestProblem3(double e)

Simple constructor.

Parameters:

e - eccentricity

TestProblem3

public TestProblem3()

Simple constructor.

TestProblem3

public TestProblem3(TestProblem3 problem)

Copy constructor.

Parameters:

problem - problem to copy

Method Detail

copy

public TestProblem3 copy()

Copy operation.

Specified by:

copy in class TestProblemAbstract

Returns:

a copy of the instance

doComputeDerivatives

public void doComputeDerivatives(double t,
                                 double[] y,
                                 double[] yDot)

Specified by:

doComputeDerivatives in class TestProblemAbstract

computeTheoreticalState

public double[] computeTheoreticalState(double t)

Description copied from class: TestProblemAbstract

Compute the theoretical state at the specified time.

Specified by:

computeTheoreticalState in class TestProblemAbstract

Parameters:

t - time at which the state is required

Returns:

state vector at time t