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<h2 title="Class FirstOrderConverter" class="title">Class FirstOrderConverter</h2>
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<dd><a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">FirstOrderDifferentialEquations</a></dd>
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<pre>public class <span class="strong">FirstOrderConverter</span>
extends <a href="http://docs.oracle.com/javase/7/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a>
implements <a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">FirstOrderDifferentialEquations</a></pre>
<div class="block">This class converts second order differential equations to first
order ones.
<p>This class is a wrapper around a <a href="../../../../../org/apache/commons/math3/ode/SecondOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode"><code>SecondOrderDifferentialEquations</code></a> which allow to use a <a href="../../../../../org/apache/commons/math3/ode/FirstOrderIntegrator.html" title="interface in org.apache.commons.math3.ode"><code>FirstOrderIntegrator</code></a> to integrate it.</p>
<p>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.</p>
<p>One should be aware that the data is duplicated during the
transformation process and that for each call to <a href="../../../../../org/apache/commons/math3/ode/FirstOrderConverter.html#computeDerivatives(double,%20double[],%20double[])"><code>computeDerivatives</code></a>, this wrapper does copy 4n
scalars : 2n before the call to <a href="../../../../../org/apache/commons/math3/ode/SecondOrderDifferentialEquations.html#computeSecondDerivatives(double,%20double[],%20double[],%20double[])"><code>computeSecondDerivatives</code></a> 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.</p></div>
<dl><dt><span class="strong">Since:</span></dt>
<dd>1.2</dd>
<dt><span class="strong">See Also:</span></dt><dd><a href="../../../../../org/apache/commons/math3/ode/FirstOrderIntegrator.html" title="interface in org.apache.commons.math3.ode"><code>FirstOrderIntegrator</code></a>,
<a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode"><code>FirstOrderDifferentialEquations</code></a>,
<a href="../../../../../org/apache/commons/math3/ode/SecondOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode"><code>SecondOrderDifferentialEquations</code></a></dd></dl>
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<td class="colOne"><code><strong><a href="../../../../../org/apache/commons/math3/ode/FirstOrderConverter.html#FirstOrderConverter(org.apache.commons.math3.ode.SecondOrderDifferentialEquations)">FirstOrderConverter</a></strong>(<a href="../../../../../org/apache/commons/math3/ode/SecondOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">SecondOrderDifferentialEquations</a> equations)</code>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/ode/FirstOrderConverter.html#computeDerivatives(double,%20double[],%20double[])">computeDerivatives</a></strong>(double t,
double[] y,
double[] yDot)</code>
<div class="block">Get the current time derivative of the state vector.</div>
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<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/ode/FirstOrderConverter.html#getDimension()">getDimension</a></strong>()</code>
<div class="block">Get the dimension of the problem.</div>
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<h4>FirstOrderConverter</h4>
<pre>public FirstOrderConverter(<a href="../../../../../org/apache/commons/math3/ode/SecondOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">SecondOrderDifferentialEquations</a> equations)</pre>
<div class="block">Simple constructor.
Build a converter around a second order equations set.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>equations</code> - second order equations set to convert</dd></dl>
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<pre>public int getDimension()</pre>
<div class="block">Get the dimension of the problem.
<p>The dimension of the first order problem is twice the
dimension of the underlying second order problem.</p></div>
<dl>
<dt><strong>Specified by:</strong></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html#getDimension()">getDimension</a></code> in interface <code><a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">FirstOrderDifferentialEquations</a></code></dd>
<dt><span class="strong">Returns:</span></dt><dd>dimension of the problem</dd></dl>
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<h4>computeDerivatives</h4>
<pre>public void computeDerivatives(double t,
double[] y,
double[] yDot)</pre>
<div class="block">Get the current time derivative of the state vector.</div>
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<dt><strong>Specified by:</strong></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html#computeDerivatives(double,%20double[],%20double[])">computeDerivatives</a></code> in interface <code><a href="../../../../../org/apache/commons/math3/ode/FirstOrderDifferentialEquations.html" title="interface in org.apache.commons.math3.ode">FirstOrderDifferentialEquations</a></code></dd>
<dt><span class="strong">Parameters:</span></dt><dd><code>t</code> - current value of the independent <I>time</I> variable</dd><dd><code>y</code> - array containing the current value of the state vector</dd><dd><code>yDot</code> - placeholder array where to put the time derivative of the state vector</dd></dl>
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