Class FirstOrderConverter
 All Implemented Interfaces:
OrdinaryDifferentialEquation
This class is a wrapper around a SecondOrderODE
which
allow to use a ODEIntegrator
to integrate it.
The transformation is done by changing the n dimension state vector to a 2n dimension vector, where the first n components are the initial state variables and the n last components are their first time derivative. The first time derivative of this state vector then really contains both the first and second time derivative of the initial state vector, which can be handled by the underlying second order equations set.
One should be aware that the data is duplicated during the
transformation process and that for each call to computeDerivatives
, this wrapper does copy 4n
scalars : 2n before the call to computeSecondDerivatives
in order to dispatch the y state vector
into z and zDot, and 2n after the call to gather zDot and zDDot
into yDot. Since the underlying problem by itself perhaps also
needs to copy data and dispatch the arrays into domain objects,
this has an impact on both memory and CPU usage. The only way to
avoid this duplication is to perform the transformation at the
problem level, i.e. to implement the problem as a first order one
and then avoid using this class.

Constructor Summary

Method Summary
Modifier and TypeMethodDescriptiondouble[]
computeDerivatives
(double t, double[] y) Get the current time derivative of the state vector.int
Get the dimension of the problem.Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface org.hipparchus.ode.OrdinaryDifferentialEquation
init

Constructor Details

FirstOrderConverter
Simple constructor. Build a converter around a second order equations set. Parameters:
equations
 second order equations set to convert


Method Details

getDimension
public int getDimension()Get the dimension of the problem.The dimension of the first order problem is twice the dimension of the underlying second order problem.
 Specified by:
getDimension
in interfaceOrdinaryDifferentialEquation
 Returns:
 dimension of the problem

computeDerivatives
public double[] computeDerivatives(double t, double[] y) Get the current time derivative of the state vector. Specified by:
computeDerivatives
in interfaceOrdinaryDifferentialEquation
 Parameters:
t
 current value of the independent time variabley
 array containing the current value of the state vector Returns:
 time derivative of the state vector
